Pillar-Layered Metal–Organic Framework with Sieving Effect and Pore

Aug 9, 2017 - Xu-Jia Hong, Qin Wei, Yue-Peng Cai , Bing-bing Wu, Hai-Xing Feng, Ying Yu, and Ren-Feng Dong. School of Chemistry and Environment, ...
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A Pillar-Layered Metal-Organic Framework with Sieving Effect and Pore Space Partition for Effective Separation of Mixed Gas C2H2/C2H4 Xu-Jia Hong, Qin Wei, Yuepeng Cai, Bing-Bing Wu, Hai-Xing Feng, Ying Yu, and Ren-Feng Dong ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.7b10420 • Publication Date (Web): 09 Aug 2017 Downloaded from http://pubs.acs.org on August 10, 2017

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A Pillar-Layered Metal-Organic Framework with Sieving Effect and Pore Space Partition for Effective Separation of Mixed Gas C2H2/C2H4 Xu-Jia Hong, Qin Wei, Yue-Peng Cai,* Bing-bing Wu, Hai-Xing Feng, Ying Yu and Ren-Feng Dong* School of Chemistry and Environment, Guangzhou Key Laboratory of Materials for Energy Conversion and Storage, Guangdong Provincial Engineering Technology Research Center for Materials for Energy Conversion and Storage South China normal University Guanghzou, 510006, P. R. China. Corresponding author E-mail: [email protected], [email protected]

ABSTRACT: The removal of acetylene from the industrial feed gas to purify the ethylene is an important and challenging issue. The adsorption-based separation is a more environmental friendly and cost effective method compared with the current removal approaches such as partial hydrogenation and solvent extraction while facing the challenge of developing materials with high C 2H2/C2H4 selectivity and C2H2 capacity. Herein, by expanding Mixed-Metal Organic Frameworks (M’MOFs) structure with high C2H2/C2H4 selectivity, we report a pillar-layered MOF, {[Cd5(MPCZ)2(BDC)3(NO3)2(H2O)4]·G}n (MECS-5), which not only inherits the sieving effects of M’MOF series, but also develops its own characteristic-the 2D layer with expanding space and the plane pore-partition group to ‘cover’ it. MECS-5 shows higher IAST C2H2/C2H4 selectivity than the most reported MOFs, especially more than five times higher than MOF-74 series while displays great enhancement in the C2H2 capacity, more than two times higher compared with the M’MOF. The column breakthrough experiment further proves the possibility of MECS-5a for real industrial ethylene purification.

Keywords: metal-organic frameworks, pillar-layered Cd-MOF, selective adsorption, C2H2/C2H4, sieving effect, pore space partition

■INTRODUCTION Ethylene is one of the most important chemical raw materials, and polymer products based on ethylene have been widely used in people’s daily life. Due to its industrial production method of the steam cracking of hydrocarbons, however, there is usually about 1% of acetylene residue in the ethylene feed gas, and this acetylene residue will cause great trouble to the next polymerization1. So it is very necessary to purify the ethylene feed gas and the concentration of the acetylene should be reduced to the acceptable lever. The current approaches for the C 2H2/C2H4 separation in the petrochemical industry are partial hydrogenation and solvent extraction2. Unfortunately, both of them are costly and energy consumptive. The former process needs noble metal catalyst and usually loss olefin, while the later waste lots of solvent. Therefore, developing cost effective and environmental friendly separation method of acetylene and ethylene is in urgent. Using porous materials to selectively separate the gas at the normal pressure and temperature is an attractive and challenging method. The key issue is to develop the porous materials which have high selectivity and adsorption capacity for acetylene at the same time. Unhappily, the traditional porous materials, such as active carbon and zeolites, present poor performance in the C2H2/C2H4 separation due to the similarity of the two substances in the molecular dynamic radius3.

Metal-Organic Frameworks, constructed by the metal ions and organic ligands4-6, not only have high surface area but also provide the platform for scientists to design materials with particular size and chemical environments at the molecular level, which create more possibility to develop the efficient separation materials for C2H2/C2H47,8. Compared with the MOFs used for other gas separation such as CO2/CH4 and CO2/N29, until now there are only few reported MOFs used for the C2H2/C2H4 separation, for example, the series of MOF-7410, M’MOF11,12, SIXSIF13, NOTT-30014 and UTSA15,16. Among them, the M’MOF series possess good selectivity for C2H2/C2H4 because of the sieving effect but with low capacity11,12, while MOF-74 series are opposite, it has low selectivity but high capacity, only the SIXSIF series13 recently reported by Chen’s group show the excellent C2H2/C2H4 selectivity and high C2H2 uptake (Scheme 1). It is challenge and needs the careful and diligent thinking for the design and syntheses of the MOFs with high C2H2/C2H4 selectivity and C2H2 uptake. By imitating from the reported MOFs with good selectivity or capacity, and elaborately adjusting their structures may be an efficient way for developing suitable C2H2/C2H4 separation materials. We noticed that the most reported MOFs usually have high C2H2 uptake but low selectivity, while the MOFs with high selectivity are rare. It seems that it is more difficult to improve the selectivity than the capacity. The M’MOF series featured with the pillar-layered structure which is experimentally proved to be the kind of structure that is easy to control, while their

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IAST selectivity for C2H2/C2H4 can easily reach the high lever in the reported MOFs11,12 (Scheme 1). Besides, we noticed that the pores in the two-dimensional framework constructed by the ligand H2BDC and Cd(II) ions can exist in two kinds of forms: one is the small pores of triangle shape surrounded with three walls of terephthalic acids; another is the larger pore of quadrangle shape surrounded with four walls (Scheme 1)17. The 2D layers of the reported M’MOF series adopted the former, which limits the adsorption capacity. It inspire us to think if the 2D layers adopt the larger pore form while maintaining the framework of M’MOF series, the C2H2 adsorption capacity may be improved while still keeping the high selectivity. Moreover, the reported pore space partition is one of a good strategy to divide the open channel into smaller space for enhancing the interaction between the MOFs and gas which can be taken into account when designing the MOFs because the pores of the reported pillar-layered MOFs are usually open channel which is not conducive to effectively capture the target gas in the pores 18.

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pores in the 2D layer and divide the 1-D channel space into smaller segments (Scheme 1). The well-designed MECS-5 finally combines the sieving effects and pore space partition making it present high C2H2/C2H4 selectivity and C2H2 adsorption capacity (Scheme 1). ■EXPERIMENTAL SECTION Materials and physical measurements Except the ligand HMPCZ, all the reagents and solvents were purchased. The ligand HMPCZ was synthesized according to the reference19. Nicolet/Nexus-670 FT-IR spectrometer was used to collect the infrared spectra from KBr pellets in the range of 4000 - 400 cm-1. Thermogravimetric analyses (TGA) were performed on a Netzsch Thermo Microbalance TG 209 F3 Tarsus from room temperature to 800 ℃ with a heating rate of 10 ℃/min under flowing nitrogen. The X-ray powder diffraction patterns were measured on a Bruker D8 Advance diffractometer at 40 kV and 40 mA with a Cu target tube and a graphite monochromator. Synthesis of {[Cd5(MPCZ)2(BDC)3(NO3)2(H2O)4]·G}n (MECS5) Cd(NO3)2·4H2O (123.2 mg, 0.4 mmol), HMPCZ (54.2 mg, 0.2 mmol) and H2BDC(80.2 mg, 0.3 mmol) were dissolved in the mixture of DMF (4 mL). Then the mixture was sealed in a glass bottle with the cover and then heated under autogenous pressure at 100 ℃ for three days. After cooling to room temperature, yellow block-shaped crystals of MECS-5 were obtained and washed with DMF. Yield: 46% (based on the ligand). IR (KBr, cm-1): 3451(br), 2930(m), 2859(w), 1613(w), 1574(w), 1507(m), 1469(m), 1375(m), 1315(m), 1262(m), 1181(w), 1107(s), 1081(s), 982(m), 826(m), 771(m), 739(w), 620(m), 458(w). X-ray data collection and structure refinement

Scheme 1 Imitating from M’MOF to design the structure of MOF with high C 2H 2/C2H 4 selectivity and C 2H 2 uptake.

Taking all the above into account, herein by imitating from the M’MOF series, we report a pillar-layered MOF, MECS-5, constructed by the terephthalic acid and Schiff base HMPCZ liangd (HMPCZ = 2-Hydroxy-3-methoxybenzaldehyde-pyridin-3-ylcarbonylhydrazone) with Cd(II) ions (Scheme 1). Compared with M’MOF series, the layers of MECS-5 possess expanding pores, which are 2×2 grid pores (Scheme 1). In particular, the planar binuclear Cd(II) building block units constructed by the HMPCZ and the Cd(II) ions not only act as the pillars connect the 2D layer into 3D MOF, but also act as the ‘cap’ cover the 2×2 grid

Data collections were performed at 298 K on a Bruker Smart Apex II diffractometer with graphitemonochromated Mo Kα radiation (λ = 0.71073 Å) for MECS-5. Absorption corrections were applied by using the multiscan program SADABS20. Structural solutions and fullmatrix least squares refinements based on F2 were performed with the SHELXS-9721 and SHELXL-9722 program packages, respectively. All the non-hydrogen atoms were refined anisotropically. The solvent molecules in the compound are highly disordered. The SQUEEZE option in PLATON23 was used to remove the disordered solvent molecules. The hydrogen atoms on organic motives were placed at calculated position and the coordinated water hydrogen atoms were located from difference maps and refined with isotropic temperature factors. All hydrogen atoms of the coordinated solvent water molecules have been not added. Details of the crystal parameters, data

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collections, and refinements for complexes MECS-5 are summarized in Table S1. Selected bond lengths and angles are shown in Table S2. Further details are provided in Supporting Information. The CCDC number for compound MECS-5 is 1536047. Gas adsorption experiments The N2, C2H2 and C2H4 sorption measurements were performed on automatic volumetric adsorption equipment (Belsorp-max). Before gas adsorption measurements, the samples were immersed in MeOH for exchanging the guest at least 5 times and then filtered and dried at room temperature. Then the samples were activated by heating at 80C under vacuum conditions for 24h. A sample of activated MECS-5a (70–100 mg) was used for the sorption measurement and was maintained at 77K with liquid nitrogen, at 273K with an ice-water bath, at 298K with the water bath. ■RESULTS AND DISCUSSION Synthesis and structure characterization The solvothermal reaction of HMPCZ, H2BDC and Cd(NO3)2 in the mixture of the H2O and DMF solvent at 100oC for 3 days yielded the yellow crystals. The X-ray single crystal diffraction experiment showed that the yellow crystal crystallized in the monoclinic crystal system, I2/a space group and formulated as {[Cd5(MPCZ)2(BDC)3(NO3)2(H2O)4]·G}n (MECS-5). As shown in Figure S1a, the asymmetric unit of MECS-5 contains one deprotonated Schiff base ligand, MPCZ-, one and a half deprotonated terephthalic acid, BDC2-, one nitrate ion, two and a half Cd(II) ions and three coordinated solvent molecules. The selected bond length and bond angle are listed in the Table S2.

trinuclear Cd(II) building unit. The central Cd1 atom is coordinated to eight oxygen atoms from six carboxylates forming the dodecahedron coordination geometry. Then the Cd3(O2CR)6 units are linked to each other through the BDC2- to form the 2D layer with a certain thickness in the ab plane (Figures 1 and S2). As shown in Figure 1, in the 2D layer, taking the BDC2- as the wall and the Cd3(O2CR)6 units as the pillar, the 2 × 2 grid cavity can be seen with the sizes of 9.403Å × 11.408Å × 6.801Å. Thus, compared with the M’MOF series, MECS-5 possesses the expanding pore space in the 2D layer for accommodating more gas molecules. What’s more, the coordinated H2O molecules directly face the cavity, which can be removed and providing the open Cd(II) sites. At the same time, in MECS-5, two deprotonated ligand MPCZ- as well as two Cd(II) ions assembled into the planar binuclear Cd(II) building unit, [Cd2(MPCZ)2(NO3)2(H2O)2]. In the binuclear Cd(II) building unit, Cd(II) is seven coordinated to four oxygen atoms and one nitrogen atom from two MPCZ- to form the plane, leaving two oxygen atoms respectively from one nitrate ion and one coordinated H2O molecule in the axial of the plane (Figure S3). The pyridine groups in the planar binuclear Cd(II) building unit make the unit equivalent to the classical pillar, 4,4'-bipyridine, connecting the 2D layers to construct the 3D pillar-layered MOF (Figures 1 and S4). However, compared with the simple 4,4'-bipyridine, the binuclear Cd(II) unit contains the open Cd(II) sites generated by removing the coordinated H2O molecules. Thanks to the planarity of the binuclear Cd(II) unit and its dihedral angel of 53.431o between the dinuclear plane and the terminal pyridyl group, in MECS-5 the binuclear Cd(II) unit is also treated as the ‘cap’ to cover the 2×2 grid pores in the 2D layer and assumes the role of pore-partition group to divide the channel space into the smaller segments (Figure 1). Gas separation performance and mechanism

Figure 1 The pillar-layered structure of MECS-5 (C, gray; N, blue; O, red; Cd, pink; the hydrogen atoms are omitted for clarity).

The trinuclear Cd(II) building unit, Cd3(O2CR)6, can be generated by the Cd1, Cd2, Cd1#1 (#1: 0.5-x, y, -z) and the BDC2- through the symmetrical operation (Figure S1b) which is similar to the reported Cd3(O2CR)617. In the trinuclear Cd(II) building unit, the two Cd2 in the end are 7coordiante to one oxygen atom from one Ƙ1-coordinated carboxylate, two oxygen atoms from two Ƙ2-coordinated carboxylates, one oxygen atom from the coordinated H 2O molecules and one nitrogen atom from the pyridine nitrogen atom of HMPCZ in the axial position of the

Figure 2 (a) The PXRD pattern of MECS-5, (b) TGA curves of MECS-5, MECS-5 soaked in MeOH and the activated MECS-5a.

In order to remove the solvents in MECS-5, the assynthesized samples were immersed in MeOH for exchange the solvent guest at least 5 times and then filtered. Then the samples were heated at 80C under vacuum conditions for 24h to obtain the activated MECS5a. The XRD and TGA results show that the solvent

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molecules were completely removed in the activated MECS-5a while maintaining the structure (Figure 2). The N2 sorption isotherm at 77K shows a typical type-I isotherm indicating the micro porosity of MECS-5a with the Langmuir area of MECS-5a calculated to be 964 m2g-1 (Figure 3a) which is larger than the M’MOF series reflecting the expanding space of the MECS-5a.

Figure 3 (a) Adsorption isotherm of MECS-5a for N2 at 77 K; (b) adsorption isotherms of MECS-5a for C2H2 and C2H4 at 273 K and 298 K; (c) the C2H2/C2H4 selectivity for MECS-5a at 298 K calculated by the IAST method in C2H2/C2H4 (1/99) binary mixtures; (d) the Qst of MECS-5a for C2H2 and C2H4.

As shown in Figure 3b, the adsorption isotherms of C2H2 and C2H4 at 273K and 298K indicate that compound MECS5a have obviously different adsorption amount for C2H2 and C2H4. The uptake amounts of MECS-5a for C2H2 are 125.5 cm3·g-1 (3.85 mmol·g-1) at 273K and 1bar and 86.2 cm3·g-1 (2.74 mmol·g-1) at 298K and 1bar. For C2H4, the uptake amounts are quite few, only 34.6 cm 3·g-1 (1.54 mmol·g-1) at 273K and 25.5 cm3·g-1 (1.14 mmol·g-1) at 298K, respectively. Compared with the M’MOF series11,12, the adsorption amount of MECS-5a for C2H2 is improved (Table S3) which could be attributed to the larger specific surface area coming from the expanding space in the 2D layer and the smaller segments divided by the dinuclear Cd(II) plane pore-partition group. Though the C2H2 uptake amount of MECS-5a is smaller than the other MOFs, such as MOF-7410 and NOTT-100a15, the C2H4 uptake amount of MECS-5a is far smaller which reveals the better selectivity of MECS-5a. To investigate the C2H2 selectivity, the ideal adsorption solution theory (IAST) base method (Figure 3c) was used to calculated the separation selectivity of C2H2 versus C2H4 in the binary C2H2/C2H4 mixtures containing 1% C2H2 to simulate the typical industrial mixture. As shown in Figure 3c, the selectivity of C2H2/C2H4 displayed the decreasing trend from 17.5 to 12.6 in the range of 0-100KPa. At 100KPa and 298K, the selectivity of compound MECS-5a is higher than the most reported MOFs, such as the MOF-74 series, NOTT-300 (~5.5), UTSA-100a (10.72), and similar to the M’MOF-4a (14.4) (Table S3). The high selectivity of

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MECS-5a could be attributed to the sieving effects coming from the similar structure of MECS-5a and M’MOF series which have been reported possessing high selectivity of C2H2/C2H4. More importantly, we found that there are three small pore windows in MECS-5a, 4.5×5.3Å , 3.4×4.5Å,1.8×3.9Å (Figure S5, Table S3). It is more easy for the C2H2 to get inside the pores because of the smaller empirical kinetic diameters. The scatter diagram in Scheme 1 shows the distribution diagram of the adsorption amount and the IAST calculation C2H2/C2H4 selectivity for MECS-5a and some reported typical MOFs. We can find that there are only a few MOFs possess both high C2H2 uptake and C2H2/C2H4 selectivity, and most MOFs possess either high C2H2 uptake with low selectivity or high selectivity with low C2H2 uptake. Besides, the most reported MOFs featured with high C2H2 uptake but low selectivity while the MOFs with high selectivity are rare. Imitating from the M’MOF series, the pillar-layered MECS-5a not only inherits the high C2H2/C2H4 selectivity of M’MOF series deriving from the sieving effects and pore space partition, but also possesses moderate C2H2 uptake amount due to the expanding space in the 2D layer. All these factors contribute to the high C2H2 uptake and C2H2/C2H4 selectivity of MECS-5a.

Figure 4 The column breakthrough experiment for C2H2/C2H4 (1:99, v/v) mixture at 298 K and 1 bar in MECS-5a.

In order to further test the performance of MECS-5a in the actual adsorption-based separation and purification processes, the powder of MECS-5a was packed in the column with the C2H2/C2H4 (1:99, v/v) mixture flowing over at 298K. It is clearly that MECS-5a could successfully separate the C2H2 from the feed gas (Figure 4). The breakthrough points of C2H4 and C2H2 are 3.85mmol/g and 8.38mmol/g respectively and the purity of C2H4 could successfully achieve > 99.996% (Figure S10). What’s more, the MECS-5a also presented the good structural stability and regenerability as shown in Figure S7 and S10 which proves the possibility of MECS-5a for real industrial ethylene purification.

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To better understand adsorption of MECS-5a for C2H2, the GCMC and DFT calculation were carried out to calculate the possible adsorption sites in MECS-5a. Figure 5 shows the specific spatial possibility distribution illustrating the tendency of particles after equilibrium. The distribution of acetylene is mostly in the round of the plane pore-partition group and the Cd3(O2CR)6 units in the 2D layer. It can be seen that there is a higher density distribution around the plane pore-partition group. This is because that the pore-partition group exists the unsaturated coordination Cd (II) ions which can provide the interaction sites for C2H2 (Figure 6a). Besides, the hydrogen bond between the oxygen from the coordinated nitrate ion and the acetylene molecular associates with the π…π interaction between the acetylene molecule and the benzene ring of ligand providing the adsorption site for C2H2 as well (Figure 6b). In the 2D layer of MECS-5a, the open-metal sites at the ends of Cd3(O2CR)6 units and the aromatic rings of the terephthalic acids provide the adsorption sites (Figure 6c). From the distribution of C2H2 in MECS-5a, it is clear that the dinuclear plane porepartition group play an important role in the adsorption of C2H2. On the one hand, the planarity of the pore-partition group and the functional sites provide rich interaction sites for acetylene molecules. On the other hand, it subdivides the channel into more independent units and limits the acetylene molecules in the narrow space.

the M’MOF series with high C2H2/C2H4 selectivity, we report a pillar-layered MOF, MECS-5, which inherits the sieving effects of M’MOF to limit the adsorption of ethylene. It is interesting that the expanding space in 2D layer compared with M’MOFs make it possible to capture more acetylene while the planar pore-partition group limit acetylene in the narrow space to ensure the high selectivity and adsorption capacity at the same time. Obviously, this work not only successfully develops the potential separation materials for real industrial ethylene purification, but also provides the example of designing MOFs with better separation performance based on the structure of reported MOFs.

Acknowledgements The authors are grateful for financial aid from the National Natural Science Foundation of P. R. China (Grant No.21471061, 21671071 and 21575043), the National Natural Science Foundation of Guangdong Province (Grant No. 2014A030311001), Scientific Research Foundation of Graduate School of South China Normal University (Grant No. 2016lkxm06), Applied Science and Technology Planning Project of Guangdong Province, Guangzhou, China (No. 2015B010135009), Innovation team project of Guangdong Ordinary University (No. 2015KCXTD005), the great scientific research project of Guangdong Ordinary University (No. 2016KZDXM023).

Supporting Information Available: Additional structural figures, selected bond lengths, bond angles, crystal data, PXRD patterns, fitting for sorption isotherms, and tables (PDF) The report of checkcif (PDF) CIF file for MECS-5 (CIF)

Notes and references Figure 5. Spatial possibility distribution of C2H2 in MECS-5a along c axis (left ) and a axis (right).

Figure 6. The possibility binding sites of (a) the unsaturated coordination Cd (II) ions; (b) the hydrogen bond and the π…π interaction; (c) the open-metal sites at the ends of Cd3(O2CR)6 units and the aromatic rings of the terephthalic acids for C2H2 in MECS-5a.

Conclusions In summary, in order to construct the MOFs with high C2H2/C2H4 selectivity and C2H2 capacity, by imitating from

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C.-H.; Sun, D., Beyond Clusters: Supramolecular Networks Self-Assembled from Nanosized Silver Clusters and Inorganic Anions. Chem. Eur. J. 2016, 22 (20), 6830-6836. 6. Yuan, S.; Deng, Y.-K.; Sun, D., Unprecedented SecondTimescale Blue/Green Emissions and Iodine-UptakeInduced Single-Crystal-to-Single-Crystal Transformation in ZnII/CdII Metal–Organic Frameworks. Chem. Eur. J. 2014, 20 (32), 10093-10098. 7. Li, J.-R.; Sculley, J.; Zhou, H.-C., Metal–Organic Frameworks for Separations. Chem. Rev. 2012, 112 (2), 869-932. 8. Cui, Y.; Li, B.; He, H.; Zhou, W.; Chen, B.; Qian, G., Metal–Organic Frameworks as Platforms for Functional Materials. Accounts Chem. Res. 2016, 49 (3), 483-493. 9. Wang, X.-P.; Chen, W.-M.; Qi, H.; Li, X.-Y.; Rajnák, C.; Feng, Z.-Y.; Kurmoo, M.; Boča, R.; Jia, C.-J.; Tung, C.-H.; Sun, D., Solvent-Controlled Phase Transition of a CoIIOrganic Framework: From Achiral to Chiral and Two to Three Dimensions. Chem. Eur. J. 2017, 23 (33), 79907996. 10. He, Y.; Krishna, R.; Chen, B., Metal–organic frameworks with potential for energy-efficient adsorptive separation of light hydrocarbons. Energ. Environ. Sci. 2012, 5 (10), 9107-9120. 11. Xiang, S. C.; Zhang, Z.; Zhao, C. G.; Hong, K.; Zhao, X.; Ding, D. R.; Xie, M. H.; Wu, C. D.; Das, M. C.; Gill, R.; Thomas, K. M.; Chen, B., Rationally tuned micropores within enantiopure metal-organic frameworks for highly selective separation of acetylene and ethylene. Nat. Commun. 2011, 2, 204. 12. Das, M. C.; Guo, Q.; He, Y.; Kim, J.; Zhao, C. G.; Hong, K.; Xiang, S.; Zhang, Z.; Thomas, K. M.; Krishna, R.; Chen, B., Interplay of metalloligand and organic ligand to tune micropores within isostructural mixed-metal organic frameworks (M'MOFs) for their highly selective separation of chiral and achiral small molecules. J. Am. Chem. Soc. 2012, 134 (20), 8703-8710. 13. Cui, X.; Chen, K.; Xing, H.; Yang, Q.; Krishna, R.; Bao, Z.; Wu, H.; Zhou, W.; Dong, X.; Han, Y.; Li, B.; Ren, Q.; Zaworotko, M. J.; Chen, B., Pore chemistry and size control in hybrid porous materials for acetylene capture from ethylene. Science 2016, 353, 141-144. 14. Yang, S.; Ramirez-Cuesta, A. J.; Newby, R.; Garcia-Sakai, V.; Manuel, P.; Callear, S. K.; Campbell, S. I.; Tang, C. C.; Schroder, M., Supramolecular binding and separation of hydrocarbons within a functionalized porous metalorganic framework. Nat. Chem. 2014, 7 (2), 121-129. 15. Hu, T. L.; Wang, H.; Li, B.; Krishna, R.; Wu, H.; Zhou, W.; Zhao, Y.; Han, Y.; Wang, X.; Zhu, W.; Yao, Z.; Xiang, S.; Chen, B., Microporous metal-organic framework with dual functionalities for highly efficient removal of acetylene from ethylene/acetylene mixtures. Nat. Commun. 2015, 6, 7328. 16. Wen, H. M.; Li, B.; Wang, H.; Wu, C.; Alfooty, K.; Krishna, R.; Chen, B., A microporous metal-organic framework with rare lvt topology for highly selective C2H2/C2H4 separation at room temperature. Chem. Commun.

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ACS Applied Materials & Interfaces

TOC Graphic A Pillar-Layered Metal-Organic Framework with Sieving Effect and Pore Space Partition for Effective Separation of Mixed Gas C2H2/C2H4 Xu-Jia Hong, Qin Wei, Yue-Peng Cai,* Bing-bing Wu, Hai-Xing Feng, Ying Yu and Ren-Feng Dong* School of Chemistry and Environment, Guangzhou Key Laboratory of Materials for Energy Conversion and Storage, Guangdong Provincial Engineering Technology Research Center for Materials for Energy Conversion and Storage South China normal University Guanghzou, 510006, P. R. China.

Imitating from M’MOF series, with expanding space in the 2D layer and the plane pore-patition group covering the space in the pillar, a pillar-layered Cd-MOF (namely MECS-5) showing sieving effect and pore space partition for the C2H2/C2H4 separation presents high selectivity and adsorption capacity for C2H2.

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