Rapid, Microwave-Assisted Synthesis of Cubic, Three-Dimensional

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Article

Rapid microwave-assisted synthesis of cubic 3D highly porous MOF-205 for room temperature CO fixation via cyclic carbonate synthesis 2

Robin Babu, Roshith Roshan Kuruppathparambil, Amal Cherian Kathalikkattil, Dongwoo Kim, and Dae-Won Park ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b12458 • Publication Date (Web): 18 Nov 2016 Downloaded from http://pubs.acs.org on November 19, 2016

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ACS Applied Materials & Interfaces

Rapid microwave-assisted synthesis of cubic 3D highly porous MOF-205 for room temperature CO2 fixation via cyclic carbonate synthesis Robin Babu,1 Roshith Roshan,1Amal Cherian Kathalikkattil,2 Dong Woo Kim,3 and Dae-Won Park 1* (1)

Division of Chemical and Biomolecular Engineering, Pusan National University, Busan,

609-735, Korea (2)

School of Chemistry, University of Dublin, Trinity College, Dublin 2, Ireland

(3)

Chemical Industry Development Center Ulsan Chemical R&D Division Korea Research

Institute of Chemical Technology

KEYWORDS: Metal-organic framework, microwave synthesis, catalysis, carbon dioxide, epoxides, cyclic carbonates. 1

ACS Paragon Plus Environment


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Abstract A dual-porous three-dimensional (3D) metal-organic framework [Zn4O(2,6NDC)(BTB)4/3] (MOF-205, BET = 4200 m2/g) has been synthesized using microwave power as an alternative energy source for the first time, and its catalytic activity has been exploited for the CO2-epoxide coupling reactions to produce five membered cyclic carbonates under solvent-free conditions. Microwave synthesis was performed in different time intervals to reveal the formation of the crystals. Significant conversion of various epoxides was obtained at room temperature, with excellent selectivity toward the desired five-membered cyclic carbonates. The importance of dual-porosity and the synergistic effect of quaternary ammonium salts on efficiently catalyzed CO2 conversion were investigated using various experimental and physicochemical characterization techniques, and the results were compared with those of the solvothermally synthesized MOF-205 sample. Based on literature and experimental inferences, a rationalized mechanism mediated by the zinc center of MOF205 for CO2-epoxide cycloaddition reaction has been proposed.

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Introduction The rising levels of CO2 have been the area of concern globally over several decades now, owing to its obvious detrimental effects in the biosphere. While the debate on whether CO2 actually contributes to global warming is ongoing, a bright side of this higher availability of CO2 is that, it is an abundant, renewable C1 feedstock with high possibility for valorization1-2. Besides, the non-flammability, non-toxic and easy to handle nature of CO2 has attracted the attention of researchers worldwide to exploit this carbon source to employ for several organic transformations. The chemical conversion of CO2 into five membered cyclic carbonates has been widely acknowledged as an industrially important transformation fulfilling typical green chemistry credentials. The 100% atom-economic ring expansion reaction of epoxides with CO2 yielding cyclic carbonates is a well-known and established procedure catalyzed by a library of various homo- and heterogeneous catalysts, such as simple metal oxides, Schiff bases, salen complexes, and supported ionic liquid catalysts.3-8 Previous reports on the cycloaddition of CO2 and epoxides suggest that bifunctional catalysts having either Lewis acid/base sites or Lewis acid with a strong nucleophile can easily catalyze the CO2-epoxide cycloadditions.9-12 Recently, most researches were focused on the development of metal-organic frameworks (MOFs), as an efficient heterogeneous catalytic system for materializing the epoxide-CO2 transformation under mild conditions, that feature easier separation and reusability, together with non-leaching properties.13-15 The connectivity in MOFs is driven by the coordination between metal nodes and functionalized organic linkers, which creates empty spaces (pores) in the interior of the crystallites that can be accessed from the exterior of the substrates, permitting mass transfer in and out of the fabric. The uniformity of the catalytic active sites results in higher product 3



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selectivities of MOFs than that of conventional solid-supported catalysts, where the coordination environments are inhomogeneous. Besides, MOFs possess additional advantages such as high surface area, ordered pore structure, tunability of particle size/pore volume/pore aperture, high CO2 adsorption capability, and innumerable acidic/basic sites enhancing the possibility of epoxide-CO2 interaction.16-20 Ever since the first report of cycloaddition using MOF catalysts in 2009 by Han et al., various MOFs with different linker connectivities, such as metal-carboxylate, metal-Ndonor, and mixed metal carboxylate/N-donor linkages have been extensively studied by researchers worldwide, including our own group.21-30 In our endeavor to extend the study towards room-temperature cycloaddition reactions, we noticed that the roles of multiligand MOFs with ultra-high porosity have seldom been studied. As the current research is directed at finding easily synthesizable catalysts in an energy-efficient manner, employing microwave irradiation offers the advantages of shorter reaction time, better energy efficiency, simplicity, uniform particle morphology, and excellent phase purity; the highly porous materials of this type open up a promising area of research that ensures ecologically safer carbon dioxide fixation technologies. In our previous work, we have reported the synthesis and catalytic applications of ionic liquids, biopolymer-based catalysts, and, most recently, MOFs in cycloaddition reactions by exploring the potential of microwaves as an alternative energy source.7,23,31 In this work, a highly porous three-dimensional (3D) MOF (MOF-205) featuring Zn4O SBU units with tritopic H3BTB and ditopic H2NDC linkers was synthesized using microwave power for the first time. The structural peculiarities and physical properties of this MOF were also exploited for room-temperature CO2 fixation, and the results were compared with those of the solvothermally synthesized MOF-205 sample (Scheme 1). 4


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Results and discussion The introduction of both organic and inorganic ligands results in the formation of MOFs with different topology and structural properties, gives a suitable coordination mode to achieve specific properties and applications. Structural analysis and physical characterization were carried out in detail. MOF-205, formulated as [Zn4O(2,6-NDC)(BTB)4/3], adopts a dualporous 3D framework and crystallizes in the cubic system (pm3n space group, ith-d topology).32-33 The framework of this material consists of Zn4O clusters linked by tritopic H3BTB and ditopic H2NDC ligands, with these building blocks assembled into a structure containing both micro- and mesopores. The micropores are found in cage-like structures built from four Zn4O clusters, two 2,6-Naphthalenedicarboxylate units, and four BTB units, whereas the mesopore dodecahedral cages are formed from [Zn4O]6+ units, eight BTB units, and four 2,6-Naphthalenedicarboxylate units. The coordination environments created by ligands around Zn2+ centers and their packing are depicted in Figure 1. A comparison of MOF-5, MOF-177, and MOF-205 revealed that all of them feature the same Zn4O(CO2)6 connector unit, but exhibit different topologies due to the variance in the number, orientation, and nature of potential functional groups that can bind to the cluster. The average Zn–Zn distance for MOF-205 was measured to be around 3.3 Å, with that of Zn–O around 2.0 Å and that of C–O around 1.3 Å, being almost the same as those of MOF-5 and MOF-177.34-35 MOF-205 was solvothermally synthesized using a method similar to that reported by Kaskel et al. and was denoted as MOF-205(S).33 MOF-205(M) was synthesized using microwave power as an alternative energy source. The experimental setup consists of a multimode microwave reactor (KMIC-2 KW) which can be operated at a frequency of 2.450 GHz, provided with power source which can be adjusted continuously in the range of 0-2 kW. 5



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In a typical experiment, 142 mg Zn(NO3)2·4H2O (0.543 mmol), 17 mg H2(2,6-NDC) (0.079 mmol), and 54 mg H3(BTB) (0.123 mmol) were separately dissolved in 10 mL Diethylformamide. After sonicating for 5 min, the resulting solution was transferred into a 40 mL glass reactor. The glass reactor was closed tightly inside the microwave reactor and irradiated using a power of 200 W for 20 min. The cut-off temperature was kept at 150 °C, in view of the stability of the Pyrex glass microwave reactor. After the reaction, the reactor was allowed for natural cooling to room temperature. The produced crystals were washed several times with DEF to remove impurities and unreacted starting materials. The final product was soaked in dichloromethane (≥ 99.8%, Sigma-Aldrich) and replenishing it for two days, followed by thermal activation at 100 °C for 24 h under vacuum to free up the pores. The reason for choosing solvent exchange instead of employing high temperature for solvent removal was to minimize the energy consumption. Elemental analysis calculated (%) for C48H27NO13Zn4: C 53.03, H 2.50, O 19.13, N 8.09 (From DEF solvent), Zn 24.05; found: C 52.90, H 3.02, O 18.80, N 7.54, Zn 24.52. The phase purity, structural integrity, and bulk homogeneity of both solvothermal and microwave-synthesized MOF-205 were characterized by powder X-ray diffraction (XRD) (Figure 2). The experimental XRD pattern was compared with the one simulated based on crystallographic information files in the single crystal database. Microwave assisted synthesis was carried out in different time intervals to reveal the formation of the crystals. FESEM was used to survey the morphology of the crystals collected at different reaction times (Figure 3). Extension of the reaction time from 5 to 10 min showed that the crystals were still underdeveloped, with some unreacted precursors attached. The full growth of crystals was completed after 20 minutes. The similarities of the experimental and simulated XRD patterns 6


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confirm that the bulk of 3D-MOF-205(S) and 3D-MOF-205(M) samples are similar and pure crystalline phases. The compositional similarity of both MOF-205(S) and MOF-205(M) was proven by FTIR analysis (Figure 4). The resemblance of observed peaks for both MOF-205(S) and MOF-205(M) confirms that chemical integrity is preserved even upon adopting a microwaveassisted synthetic method. Thermogravimetric analysis (TGA) was conducted from room temperature to 600 °C to assess the material stability, robustness, and the nature of framework construction. The solvent was completely removed from the pores of the catalyst before thermal analysis. As depicted in Figure 5, the onset of framework degradation for both samples was at approximately 400 °C, further corroborating the resemblances in the thermal stability of both MOF-205(S) and MOF-205(M) catalysts. The specific surface area, average pore sizes, and micro/mesopore volume of the catalysts generally play significant roles in enhancing the CO2-epoxide cycloaddition reactions. The surface area studies of MOF-205(M) were done with nitrogen gas at 77 K. A typical type-IV isotherm was observed with a very high surface area of 4200 m2 g−1 (Figure S1). In particular, our microwave-assisted MOF-205 material exhibited a BET surface area almost identical to the one previously reported for the solvothermally synthesized sample.32 Temperature-programmed desorption (TPD) analysis was performed to calculate the potential acidic and basic sites present in MOF-205(M). CO2TPD analysis showed that the latter sample possessed a total of 62.2 mmol/g of basic sites (Figure S2). The presence of carboxylate groups around the Zn4O paddle-wheel units is responsible for CO2 adsorption. Similarly, NH3-TPD analysis showed that MOF-205(M) possessed 4.4 mmol/g of acidic sites, corresponding to the zinc metal centers (Lewis-acidic sites) (Figure S3). 7



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To evaluate the catalytic potentials of MOF-205(S) and MOF-205(M), a series of terminal and internal epoxides were examined in the coupling reaction of CO2 with epoxides to produce cyclic carbonates. Propylene oxide was chosen as primary epoxide system for the reactions. The initial screening reactions were performed under solvent-free conditions for 24 h at room temperature and 1.2 MPa CO2 pressure. Neither MOF-205(S) (0.6 mol%) nor MOF-205(M) (0.6 mol%) produced any noticeable conversion for PO under the same reaction conditions mentioned above (Table 1, Entry 3 and 4). It is well known that the use of nucleophilic co-catalysts such as tetraalkylammonium halides NR4X (R = Et, Bu) in conjugation with a Lewis acid is often beneficial for producing cyclic carbonates from epoxides and CO2, for which tetrabutylammonium bromide (TBAB) was chosen as a suitable candidate. A significant increase in PO conversion was obtained for the MOF-205(S)/TBAB and MOF-205(M)/TBAB system (Table 1, Entry 6, 7). To ascertain the role of the MOF environment in the catalysis, another set of control experiments were also conducted with the precursors of MOF-205 catalyst (Table 1, Entry 6). MOF-205(S)/TBAB system displayed an 89% conversion for PO along with > 99% selectivity. On the other hand, MOF205(M)/TBAB achieved 92% conversion for PO along with > 99% selectivity. Thus, the microwave-assisted method facilitates a faster route for catalyst synthesis than the conventional solvothermal method, while maintaining the essential catalytic activity under room-temperature reaction conditions. To investigate the effect of halide ions in the tetraalkylammonium salt, the reactions were also performed with tetrabutylammonium iodide (TBAI) and tetrabutylammonium chloride (TBAC) co-catalysts (Table 1, Entry 8, 9). The observation that bromide ion renders higher activity than iodide leads to the conclusion that, the reaction occurs primarily in micropores, not on the external surface of the framework.

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Eventhough, the ionic size differences between the free iodide and bromide are not so high, it is more probable for the bromide attached ring opened epoxide (key intermediate during the catalysis) to move freely through the micropore cages of the MOF whereby they will be more exposed to the CO2 molecules.36-37 Effect of catalyst amount in catalyzing the cycloaddition reaction was investigated using MOF-205(M) catalyst under semi-batch operation conditions. An increase in the PO conversion was noticed when the catalyst amount was increased from 0 to 0.6 mol% (Figure 6). The reaction did not proceed promisingly after reaching the maximal conversion of 92% at 0.6mol%. Hence the MOF-205(M): TBAB ratio was fixed as 1 (0.6 mol% each) for further studies. Time-dependent catalytic activity studies of the MOF-205(M) catalyst showed that the PO conversion gradually increased within the range of 0 to 24 h (Figure 7). The reaction did not proceed promisingly after reaching the maximal conversion of 92% at 24 h. Effect of reaction temperature on the test reaction was carried out at different time intervals using MOF-205(M) catalyst. The catalytic activity progressively increased from RT to 50 °C, whereby PC yields of 90 and 91% were reached in 10 h (40 °C) and 6 h (50 °C), respectively. The turnover frequency (TOF) calculated for MOF-205(M) catalyst was shown in Table S1. It was found that the TOF of the MOF-205(M)/TBAB catalyst increased from 7 (RT), 15 (40 °C) to 26 (50 °C). Based on the experimental data and our previous works using Density Functional Theory DFT) calculations,22 a plausible mechanism for the CO2-epoxide cycloaddition reaction catalyzed by MOF-205(M) is illustrated in Scheme 2. The coordinatively unsaturated Zn centers of the paddle-wheel unit act as Lewis-acidic sites which coordinate to the epoxides. The Br– ion from tetrabutylammonium bromide results in the ring opening of the epoxide. 9



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Then, the O- of the ring opened epoxide attacks the carbon atom of CO2, results in the formation of a carbonate complex (intermediate a). Finally, ring closure occurs by intramolecular carbonate O- attack on the C-Br carbon whereby PC is generated (Intermediate-b), and the regenerated catalyst moves to the next cycle of cycloaddition by coordinating the next epoxide molecule. The separation and reusability of heterogeneous catalysts are essential criterions to be considered both in laboratory and industrial processes to minimize energy and waste streams.38 We tested the recyclability for both MOF-205(S) and MOF-205(M) catalysts at RT for 24 h (Table 2). It was observed that high conversion and selectivity observed for the fresh catalysts in the first test were maintained in the next five all re-cycles for both catalysts. The structural stability and chemical integrity of the latter were well preserved even after five recycles, as confirmed by XRD (MOF-205(M): Figure 8 and MOF-205(S): Figure S4), FTIR (MOF-205(M): Figure 9 and MOF-205(S): Figure S5), and ICP-OES analysis (Table S2). The analysis of the filtrate by the latter method revealed zinc leaching of less than 1.5% after five recycles. The hydrothermal stability of the MOFs is a general issue to hinder the further applications. We soaked the MOF-205(M) catalyst in water at room temperature for one week and tested its PXRD to prove the stability. We observe that the MOF-205(M) catalyst maintained its stability towards water (Figure S6). To ascertain the versatility of MOF-205(M) in catalyzing epoxide-CO2 cycloaddition, reactions of various epoxides were also explored, with the results summarized in Table 3. Terminal aliphatic epoxides exhibited almost maximal conversion under the conditions optimized for propylene oxide. While the sterically hindered cyclohexene is not converted to any significant levels as is commonly observed with most of the metal catalyst 10


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systems. The lower reactivity of bulky epoxides compared to smaller ones leads to the conclusion that mesopores do not seem to contribute to the catalytic reaction to a large extent, but it helps in the easier mass transport of reactants and products to/from the active sites present inside the micropores. In our previous reports, we demonstrated the importance of micro-mesoporous MOFs in cycloaddition reactions, outperforming the use of pure micro- or mesoporous MOFs.39 The catalytic potentials of both MOF-205(S) and MOF-205(M) in the PO-CO2 cycloaddition reactions were compared with those of various MOFs reported earlier at room temperature conditions, and are depicted in Table 4. Initially, the activity of MOF-205(M) was compared to that of microporous MOF-5, using the reaction conditions reported for the latter catalyst (Table 4, Entry 1 and 2). MOF-5 showed a 56% PC yield, whereas the corresponding value for MOF-205(M) was 80%. These experiments were conducted at RT, 0.4 MPa CO2 over 4 h. IRMOF-3, H-Nu-1000, MMPF-9, and MMCF-2 catalysts were also found to be active in PO-CO2 cycloaddition reactions, requiring either higher catalyst/cocatalyst amounts (Table 4, Entry 3, 4, 5 and 6). Most importantly, both MOF-205(S) and MOF-205(M) catalysts maintained 100% atom economy by retaining > 99% selectivity towards the five membered cyclic carbonate products, thereby avoiding time expenses and energy-consuming separation processes. CO2 adsorption studies in MOFs prove that the surface area and pore volumes play a major role in adsorption.42 MOF-205, owning a high surface area (4200 m2/g) and pore volumes were already reported as potential candidate for CO2 capture applications.32 The presence of both micro and meso pores in one framework offers multiple benefits than each of the pure micro and meso pore regimes.25,43-44 The mesopores present in MOF-205 are ideal grooves for hosting bulky epoxides/substrates, 11



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whereas the corresponding micropores are supposed to enhance the catalyst-substrate interactions, which, taken together, results in higher catalytic activity. Thus in conclusion, the higher surface area, meso-/microporosity, and acidity/basicity of MOF-205(S) and MOF205(M) play significant roles in enhancing their catalytic performance at room temperature. Conclusion A dual-porous three-dimensional (3D) metal-organic framework [Zn4O(2,6NDC)(BTB)4/3] (MOF-205) was rapidly synthesized using microwave power, and its structural and physical properties were exploited for the CO2-epoxide coupling reactions to produce the cyclic carbonates under solvent-free conditions. The high catalytic performance of both MOF-205(S) and MOF-205(M) are attributed to the pooled effects of micro/mesoporosity and acidity/basicity. The effect of various reaction parameters that results in a maximal yield with almost 100% selectivity for the desired cyclic carbonate was also analyzed and optimized for facilitating CO2 transformation at room temperature. Thus, in general, metal organic frameworks can display outstanding performance with versatile coordination chemistry owing to a judicious selection of different mixed ligand systems that can easily control their pore size, dimensionality, and chemical environment, making them favorable candidates for different applications.

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Experimental section 1. Preparation of MOF-205 (a). Solvothermal method MOF-205 was solvothermally synthesized by a method similar to the one reported by Kaskel et al. 142 mg Zn(NO3)2·4H2O (≥ 98%, Sigma-Aldrich), 17mg H2(2,6-NDC) (99%, SigmaAldrich), and 54 mg H3(BTB) (97%, Alfa-Aesar) were separately dissolved in 20 mL DEF (99%, Alfa-Aesar). The solutions were mixed together and sonicated for 10 min and then kept in a 50 mL Teflon-lined autoclave at 100 °C for one day. After finishing the reaction time, the autoclave was kept overnight for cooling to room temperature. The produced crystals were washed several times with DEF to remove impurities and unreacted starting materials. The final product was soaked in dichloromethane (≥ 99.8%, Sigma-Aldrich) and replenishing it for two days, followed by thermal activation at 100 °C for 24 h under vacuum to free up the pores. (b). Microwave assisted method In a typical experiment, 142 mg Zn(NO3)2·4H2O (0.543 mmol), 17 mg H2(2,6-NDC) (0.079 mmol), and 54 mg H3(BTB) (0.123 mmol) were separately dissolved in 10 mL Diethylformamide. After sonicating for 5 min, the resulting solution was transferred into a 40 mL glass reactor. The glass reactor was closed tightly inside the microwave reactor and irradiated using a power of 200 W for 20 min. The cut-off temperature was kept at 150 °C, in view of the stability of the Pyrex glass microwave reactor. After finishing the reaction time, the reactor was kept overnight for cooling to room temperature. The produced crystals the produced crystals were washed several times with DEF to remove impurities and unreacted 13



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starting materials. The final product was soaked in dichloromethane (≥ 99.8%, Sigma-Aldrich) and replenishing it for two days, followed by thermal activation at 100 °C for 24 h under vacuum to free up the pores. 2. Cycloaddition of epoxides and CO2 In a typical reaction, 25 ml stainless steel autoclave reactor was filled with the predecided amounts of the catalyst, co-catalyst and epoxide. The autoclave was kept connected to a CO2 source. After finishing the reaction, the reactor was allowed to reach room temperature and the final filtrate was analyzed using gas chromatography (HP 6890, Agilent Technologies, Flame ionized detector) to determine the conversion and selectivity. Reactivity test data were obtained two times. When the difference of the two data exceeded over 5%, third analysis was conducted and the average value was taken as representative data. 3. NMR details of cyclic carbonates Propylene carbonate (4-methyl-1,3-dioxolan-2-one): 1H NMR (300 MHz, CDCl3) δ 4.77-4.72 (m, 1H, OCH), 4.48-4.42 (m, 1H, CH2), 3.94-3.89 (m, 1H, CH2), 1.35 (d, J = 6.3 Hz, 3H, CH3) Epichlorohydrin carbonate (4-(chloromethyl)-1,3-dioxolan-2-one): 1H NMR (300 MHz, CDCl3) δ 4.96-4.91 (m, 1H, OCH), 4.53-4.47 (m, 1H, CH2), 4.31-4.26 (m, 1H, CH2), 3.783.61 (m, 2H, CH2Cl) Allyl glycidyl carbonate (4-((allyloxy)methyl)-1,3-dioxolan-2-one): 1H NMR (300 MHz, CDCl3) δ 5.81-5.70 (m, 1H, CH), 5.2-5.08 (m, 2H, CH2), 4.78-4.76 (m, 1H, OCH), 4.38-4.25 (m, 2H, CH2), 3.96-3.93 (m, 2H, CH2), 3.63-3.49 (m, 2H, CH2) 14


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Styrene carbonate (4-phenyl-1,3-dioxolan-2-one): 1H NMR (300 MHz, CDCl3) δ 7.47-7.45 (m, 5H, Ph), 5.76-5.71 (m, 1H, OCH), 4.82-4.79 (m, 1H, CH2), 4.36-4.34 (m, 1H, CH2) ASSOCIATED CONTENT Supporting Information. Nitrogen adsorption-desorption isotherm of MOF-205(M), characterization of the fresh and recycled MOF-205(S) catalysts, viz., XRD, FT-IR and ICPOES. Information about various characterization techniques. AUTHOR INFORMATION Corresponding Author *Dae-Won Park Email: [email protected] Author Contributions All authors are aware of the submission and agree to its publication. ACKNOWLEDGMENT Financial support for this study is provided by the National Research Foundation of Korea (GF-HIM 2015M3A6B1065264). ABBREVIATIONS CO2, Carbon dioxide; MOF, Metal Organic Framework; BTB, 1,3,5-Tris(4-carboxy phenyl)benzene; 2,6-NDC, 2,6-Naphthalenedicarboxylic acid; TBAB, Tetrabutylammonium bromide. 15



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References 1. Lanzafame, P.; Centi, G.; Perathoner, S. Catalysis for Biomass and CO2 Use Through Solar Energy: Opening New Scenarios for a Sustainable and Low-carbon Chemical Production. Chem. Soc. Rev. 2014, 43, 7562-7580. 2. Wang, W.; Wang, S.; Ma, X.; Gong, J. Recent Advances in Catalytic Hydrogenation of Carbon Dioxide. Chem. Soc. Rev. 2011, 40, 3703-3727. 3. North, M.; Pasquale, R.; Mechanism of Cyclic Carbonate Synthesis from Epoxides and CO2. Angew. Chem. Int. Ed. 2009, 48, 2946-2948. 4. Paddock, R. L.; Nguyen, S. T.; Chemical CO2 Fixation: Cr(III) Salen Complexes as Highly Efficient Catalysts for the Coupling of CO2 and Epoxides. J. Am. Chem. Soc. 2001, 123, 11498-11499. 5. He, Q.; O'Brien, J. W.; Kitselman, K. A.; Tompkins, L. E.; Curtis, G. C. T.; Kerton, F. M. Synthesis of Cyclic Carbonates from CO2 and Epoxides Using Ionic Liquids and Related Catalysts Including Choline Chloride–metal Halide Mixtures. Catal. Sci. Technol. 2014, 4, 1513-1528. 6. Wang, J.; Wu, J.; Tang, N.; Synthesis, Characterization of a New Bicobalt Complex [Co2L2(C2H5OH)2Cl2] and Application in Cyclic Carbonate Synthesis. Inorg. Chem. Commun. 2007, 10, 1493-1495. 7. Kim, D. -W.; Roshan, R.; Tharun, J.; Cherian, A.; Park, D. -W. Catalytic Applications of Immobilized Ionic Liquids for Synthesis of Cyclic Carbonates from Carbon Dioxide and Epoxides. Korean J. Chem. Eng. 2013, 30, 1973-1984. 16


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8. Meléndez, J.; North, M.; Pasquale, R. Synthesis of Cyclic Carbonates from Atmospheric Pressure Carbon Dioxide Using Exceptionally Active Aluminium(salen) Complexes as Catalysts. Eur. J. Inorg. Chem. 2007, 3323-3326. 9. North, M.; Pasquale, R.; Young, C. Synthesis of Cyclic Carbonates from Epoxides and CO2. Green Chem. 2010, 12, 1514-1539. 10. Klaus, S.; Lehenmeier, M. W.; Anderson, C. E.; Rieger, B. Recent Advances in CO2/epoxide Copolymerization-New Strategies and Cooperative Mechanisms. Coord. Chem. Rev. 2011, 255, 1460-1479. 11. Kielland, N.; Whiteoak, C. J.; Kleij, A. W. Stereoselective Synthesis with Carbon Dioxide. Adv. Synth. Catal. 2013, 355, 2115-2138. 12. Sakakura, T.; Kazufumi, K.; The Synthesis of Organic Carbonates from Carbon Dioxide. Chem. Commun. 2009, 1312-1330. 13. Kathalikkattil, A. C.; Babu, R.; Tharun, J.; Roshan, R.; Park, D. -W. Advancements in the Conversion of Carbon Dioxide to Cyclic Carbonates Using Metal Organic Frameworks as Catalysts. Catal. Surv. Asia. 2015, 19, 223-235. 14. Beyzavi, M. H.; Stephenson, C. J.; Liu, Y.; Karagiaridi, O.; Hupp, J. T.; Farha, O. K.; Metal-organic Framework-based Catalysts: Chemical Fixation of CO2 with Epoxides Leading to Cyclic Organic Carbonates. Front. Energy Res. 2015, 2, 63-72. 15. Zhu, M.; Carreon, M. A. Porous Crystals as Active Catalysts for the Synthesis of Cyclic Carbonates. J. Appl. Polym. Sci. 2014, 131, 39738-39751. 16. Furukawa, H.; Cordova, K. E.; O’Keeffe, M.; Yaghi, O. M. The Chemistry and 17



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 18 of 39

Applications of Metal-organic Frameworks. Science. 2013, 341, 1230444-1230455. 17. Stock, N.; Biswas, S. Synthesis of Metal-Organic Frameworks (MOFs): Routes to Various MOF Topologies, Morphologies, and Composites. Chem. Rev. 2012, 112, 933-969. 18. Long, J. R.; Yaghi, O. M. The Pervasive Chemistry of Metal-organic Frameworks. Chem. Soc. Rev. 2009, 38, 1213-1214. 19. Kuppler, R. J.; Timmons, D. J.; Fang, Q. -R.; Li, J. -R.; Makal, T. A.; Young, M. D.; Yuan, D.; Zhao, D.; Zhuang, W.; Zhou, H. -C. Potential Applications of Metal-organic Framework. Coord. Chem. Rev. 2009, 253, 3042-3066. 20. Liu, J.; Chen, L.; Cui, H.; Zhang, J.; Zhang, L.; Su, C. -Y. Applications of Metal-organic Frameworks in Heterogeneous Supramolecular Catalysis. Chem. Soc. Rev. 2014, 43, 60116061. 19. Song, J.; Zhang, Z.; Hu, S.; Wu, T.; Jiang, T.; Han, B. MOF-5/n-Bu4NBr: An Efficient Catalyst System for the Synthesis of Cyclic Carbonates from Epoxides and CO2 Under Mild Conditions. Green Chem. 2009, 11, 1031-1036. 20. Miralda, C. M.; Macias, E. E.; Zhu, M.; Ratnasamy, P.; Carreon, M. A. Zeolitic Imidazole Framework-8 Catalysts in the Conversion of CO2 to Chloropropene Carbonate. ACS Catal. 2012, 2, 180-183. 21. Kuruppathparambil, R. R.; Jose, T.; Babu, R.; Hwang, G. -Y.; Kathalikkattil, A. C.; Kim, D-W.; Park, D. -W. A Room Temperature Synthesizable and Environmental Friendly Heterogeneous ZIF-67 Catalyst for the Solvent less and Co-catalyst Free Synthesis of Cyclic Carbonates. Appl. Catal. B. 2016, 182, 562-569. 18


Page 19 of 39

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


22. Kathalikkattil, A. C.; Babu, R.; Roshan, R. K.; Lee, H.; Kim, H.; Tharun, J.; Suresh, E.; Park, D. -W. An lcy-topology Amino acid MOF as Eco-friendly Catalyst for Cyclic Carbonate Synthesis from CO2: Structure-DFT Corroborated Study. J. Mater. Chem. A. 2015, 3, 22636-22647. 23. Kathalikkattil, A. C.; Kim, D. W.; Tharun, J.; Soek H. G.; Roshan, R.; Park, D. -W. Aqueous-microwave Synthesized Carboxyl Functional Molecular Ribbon Coordination Framework Catalyst for the Synthesis of Cyclic Carbonates From Epoxides and CO2. Green Chem. 2014, 16, 1607-1616. 24. Zalomaeva, O. V.; Chibiryaev, A. M.; Kovalenko, K. A.; Kholdeeva, O. A.; Balzhinimaev, B. S.; Fedin, V. P. Cyclic Carbonates Synthesis From Epoxides and CO2 Over Metal–organic Framework Cr-MIL-101. J. Catal. 2013, 298,179-185. 25. Beyzavi, M. H.; Klet, R. C.; Tussupbayev, S.; Borycz, J.; Vermeulen, N. A.; Cramer, C. J.; Stoddart, J. F.; Hupp, J. T.; Farha, O. K. A Hafnium-Based Metal−Organic Framework as an Efficient and Multifunctional Catalyst for Facile CO2 Fixation and Regioselective and Enantioretentive Epoxide Activation. J. Am. Chem. Soc. 2014, 136, 15861-15864. 26. Tharun, J.; Mathai, G.; Kathalikkattil, A. C.; Roshan, R.; Won, Y. S.; Cho, S. J.; Chang, J. S.; Park, D. -W. Exploring the Catalytic Potential of ZIF-90: Solventless and Co-CatalystFree Synthesis of Propylene Carbonate from Propylene Oxide and CO2. ChemPlusChem. 2015, 80, 715-721. 27. Yang, D. A.; Cho, H. Y.; Kim, J.; Yang, S. T.; Ahn, W. S. CO2 Capture and Conversion Using Mg-MOF-74 Prepared by a Sonochemical Method. Energy Environ. Sci. 2012, 5, 19



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 39

6465-6473. 28. Gao, W.-Y.; Chen, Y.; Niu, Y.; Williams, K.; Cash, L.; Perez, P. J.; Wojtas, L.; Cai, J.; Chen, Y. S.; Ma. S. Inserting CO2 into Aryl C-H Bonds of Metal-Organic Frameworks: CO2 Utilization for Direct Heterogeneous C-H Activation. Angew. Chem. Int. Ed. 2014, 53, 26152619. 29. Guillerm, V.; Weselinski, L. J.; Belmabkhout, Y.; Cairns, A. J.; D’Elia, V.; Wojtas, L.; Adil, K.; Eddaoudi, M. Discovery and Introduction of a (3,18)-Connected Net as an Ideal Blueprint for the Design of Metal–organic Frameworks. Nat. Chem. 2014, 6, 673-680. 30. Ren, Y.; Cheng, X.; Yang, S.; Qi, C.; Jiang, H.; Mao, Q. A Chiral Mixed Metal-organic Framework Based on a Ni(saldpen) Metalloligand: Synthesis, Characterization and Catalytic Performances. Dalton Trans. 2013, 42, 9930-9937. 31. Kathalikkattil, A. C.; Roshan, R.; Tharun, J.; Soek, H. G.; Ryu, H. S.; Park, D. -W. Pillared Cobalt-Amino Acid Framework Catalysis for Styrene Carbonate Synthesis from CO2 and Epoxide by Metal–Sulfonate–Halide Synergism. ChemCatChem. 2014, 6, 284-292. 32. Sim, J.; Yim, H.; Ko, N.; Choi, S. B.; Oh, Y.; Park, H. J.; Park, S.Y.; Kim, J. Gas Adsorption

Properties

of

Highly

Porous

Metal-organic

Frameworks

Containing

Functionalized Naphthalene Dicarboxylate Linkers. Dalton Trans. 2014, 43, 18017-18024. 33. Klein, N.; Senkovska, I.; Gedrich, K.; Stoeck, U.; Henschel, A.; Mueller, U.; Kaskel, S. A Mesoporous Metal–Organic Framework. Angew. Chem. Int. Ed. 2009, 48, 9954-9957. 34. Li, H.; Eddaoudi, M.; O'Keeffe, M.; Yaghi, O. M. Design and Synthesis of an Exceptionally Stable and Highly Porous Metal-organic Framework. Nature. 1999, 402, 27620


Page 21 of 39

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


279. 35. Saha, D.; Deng, S.; Structural Stability of Metal Organic Framework MOF-177. J. Phys. Chem. Lett. 2010, 1, 73-78. 36. Amendola, V.; Bergamaschi, G.; Boiocchi, M.; Fusco, N.; Rocca, M. V. L.; Linati, L.; Presti, E. L.; Mella, M.; Metrangolo, P.; Miljkovic, A. Novel hydrogen- and halogen-bonding anion receptors based on 3-iodopyridinium units. RSC Adv. 2016, 6, 67540-67549. 37. Kleist, W.; Jutz, F.; Maciejewski, M.; Baiker, Alfons. Mixed-Linker Metal-Organic Frameworks as Catalysts for the Synthesis of Propylene Carbonate from Propylene Oxide and CO2. Eur. J. Inorg. Chem. 2009, 3552-3561. 38. Arai, M.; Zhao, F.; Metal Catalysts Recycling and Heterogeneous/Homogeneous Catalysis. Catalysts, 2015, 5, 868-871. 39. Babu, R.; Kathalikkattil, A. C.; Roshan, R.; Tharun, J.; Kim, D. -W.; Park, D. -W. Dualporous Metal Organic Framework for Room Temperature CO2 Fixation via Cyclic Carbonate Synthesis. Green Chem. 2016, 18, 232-242. 40. Gao, W. -Y.; Wojtas, L.; Ma, S. A Porous Metal–metalloporphyrin Framework Featuring High-density Active Sites for Chemical Fixation of CO2 under Ambient Conditions. Chem. Commun., 2014, 50, 5316-5318. 41. Gao. W. -Y.; Chen, Y.; Niu, Y.; Williams, K.; Cash, L.; Perez, P. J.; Wojtas, L.; Cai, J.; Chen, Y. -S.; Ma, S. Crystal Engineering of an nbo Topology Metal–Organic Framework for Chemical Fixation of CO2 under Ambient Conditions. Angew. Chem. Int. Ed., 2014, 53, 2615 -2619. 21



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42. Liu. J.; Thallapally, P. K.; McGrail, B. P.; Brown, D. R.; Liu, J. Progress in Adsorptionbased CO2 Capture by Metal-organic Frameworks. Chem. Soc. Rev., 2012, 41, 2308-2322. 43. Kox, M. H. F.; Stavitski, E.; Groen, J. C.; Perez-Ramirez, J.; Kapteijn, F.; Weckhuysen, B. M.; Visualizing the Crystal Structure and Locating the Catalytic Activity of Micro- and Mesoporous ZSM-5 Zeolite Crystals by Using In Situ Optical and Fluorescence Microscopy. Chem. Eur. J., 2008, 14, 1718-1725. 44. Roeser, J.; Kailasam, K.; Thomas, Arne. Covalent Triazine Frameworks as Heterogeneous Catalysts for the Synthesis of Cyclic and Linear Carbonates from Carbon Dioxide and Epoxides. ChemSusChem., 2012, 5, 1793-1799.

22


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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Scheme 1. Schematic representation of the synthesis of cyclic carbonate from epoxides and CO2

23



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a

b Figure 1. “a” is the pictorial representation of the coordination environments shaped around the

zinc

metal centers

by

2,6-naphthalene

dicarboxylic

acid and

1,3,5-Tris(4-

carboxyphenyl)benzene ligands. “b” is the perspective view of MOF-205 along the c-axis depicting the arrangement of mesopores and microporous cages.

24


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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 2. PXRD patterns of both MOF-205(S) and MOF-205(M) catalysts in comparison to the single crystal simulated pattern.

25



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(a)

Page 26 of 39

(b)

(c)

(d)

(e) Figure 3. FESEM images of the microwave synthesized samples at different times: (a) 5 min (b) 10 min (c) 15 min and (d) 20 min. Figure (e) shows the FESEM image of solvothermaly synthesized samples. 26


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Figure 4. FTIR spectra of MOF-205(S) and MOF-205(M)

27



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Figure 5. Thermogravimetric analysis (TGA) of MOF-205(S) and MOF-205(M).

28


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Table 1. Catalytic screening of MOF-205(S) and MOF-205(M) in the reaction of propylene oxide (PO) with CO2 No

Catalyst

Conversion

Selectivity

(%)a

(%)a

1

None

0

-

2

TBAB

99

10b

MOF-205(S)/TBAB

80

>99

11b

MOF-205(M)/TBAB

82

>99

Reaction conditions: propylene oxide (PO) = 42.8 mmol (3 mL), 1.2 MPa PCO2, Room temperature (RT), 24 h, 600 rpm, catalyst mol% = 0.6, TBAB= 0.6 mol%, semi-batch. aFrom GC using toluene as internal standard. b: Reactions were performed under batch conditions. (GC error analysis: Run the GC three times for each sample and took the average value)

29



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Figure 6. Influence of catalyst amount MOF-205(M) on the cycloaddition of propylene oxide and CO2.

Reaction conditions: propylene oxide (PO) = 42.8 mmol (3 mL), 1.2 MPa PCO2, RT, 24 h, 600 rpm, semi-batch.

30


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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 7. Influence of reaction time on the cycloaddition of propylene oxide and CO2 using MOF-205(M) catalyst.

Reaction conditions: propylene oxide (PO) = 42.8 mmol (3 mL), 1.2 MPa PCO2, RT, 600 rpm, semi-batch.

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Page 32 of 39

Table 2. Catalyst recovery and recyclability studies No

Recycles

Conversion (%)

Selectivity (%)

Yield (%) MOF-205(S)/(M)

1

Fresh

89/92

> 99

89/92

2

1st

89/92

> 99

89/92

3

2nd

88/92

> 99

88/92

4

3rd

89/91

> 99

89/91

5

4th

89/92

> 99

89/92

6

5th

89/91

> 99

89/91

Reaction conditions: 42.8 mmol propylene oxide, 0.6 mol% MOF-205 (S)/(M), RT, 1.2 MPa PCO2, 24 h.

32


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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table 3. Substrate screening using MOF-205(M) catalyst in the reaction with CO2 Entry

Epoxide

Conversion

Selectivity

Yield

(%)

(%)

(%)

1

92

>99

92

2

82

>99

82

3

70

>99

70

4

58

>99

58

5

10

>99

10

Reaction conditions: MOF-205(M) = 0.6 mol%, TBAB = 0.6 mol%, epoxide = 42.8 mmol, PCO2 = 1.2 MPa, RT, 24 h, semi-batch.

33



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Page 34 of 39

Table 4. Comparison of the catalytic potentials of both MOF-205(S) and MOF-205(M) catalysts with previously reported MOFs at the closest reaction conditions No

Catalyst

Catalyst

Co-

Temp

Pressure

Time

PC

(mol %)

catalyst

(°C)

(MPa)

(h)

Yield

(mol %)

Ref

(%)

1

MOF-5

2.5

2.5

RT

0.4

4

56

19

2

MOF-205(M)

2.5

2.5

RT

0.4

4

80

+

3

IRMOF-3

0.64

0.64

RT

1.2

24

56

39

4

Hf-Nu-1000

4

10

RT

0.1

26

100

25

5

MMPF-9

0.13

7.2

RT

0.1

48

87

40

6

MMCF-2

0.13

7.2

RT

0.1

48

95

41

7

Cr-MIL-101

1.2

0.62

RT

0.8

24

82

24

8

UMCM-1-NH2

0.64

0.64

RT

1.2

24

90

39

9

MOF-205(S)

0.6

0.6

RT

1.2

24

89

+

10

MOF-205(M)

0.6

0.6

RT

1.2

24

92

+

Epoxide: Propylene oxide, co-catalyst: tetrabutylammonium bromide (TBAB), +: this work.

34


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Scheme 2. Proposed mechanism for the cycloaddition of PO and CO2 catalyzed by MOF205/TBAB

35



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Page 36 of 39

Figure 8. Powder XRD patterns of the fresh and recycled MOF-205(M) catalyst.

36


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Figure 9. FTIR spectra of the fresh and recycled MOF-205(M)

37



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Page 38 of 39

Graphical Abstract

38


Page 39 of 39

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22x17mm (300 x 300 DPI)


Rapid, Microwave-Assisted Synthesis of Cubic, Three-Dimensional

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