Oriented Controllable Fabrication of MetalâOrganic Frameworks

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Oriented Controllable Fabrication of Metal-Organic Frameworks Membranes as Solid Catalysts for Cascade Indole Acylation-Nazarov Cyclization for Cyclopentenone[b]indoles Chao Huang, Yingying Zhang, Haiyan Yang, Dandan Wang, Liwei Mi, Zhichao Shao, Mengjia Liu, and Hongwei Hou Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.8b01050 • Publication Date (Web): 07 Aug 2018 Downloaded from http://pubs.acs.org on August 7, 2018

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Crystal Growth & Design

Oriented

Controllable

Fabrication

of

Metal-Organic

Frameworks

Membranes as Solid Catalysts for Cascade Indole Acylation-Nazarov Cyclization for Cyclopentenone[b]indoles Chao Huang,*,† Yingying Zhang,† Haiyan Yang,† Dandan Wang,† Liwei Mi,*,† Zhichao Shao,‡ Mengjia Liu‡ and Hongwei Hou*,‡ †

Center for Advanced Materials Research, Zhongyuan University of Technology, Zhengzhou 450007,

P. R. China. ‡

College of Chemistry and Molecular Engineering, Zhengzhou University, Zhengzhou 450001, P. R.

China.

1

ACS Paragon Plus Environment

Crystal Growth & Design 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

ABSTRACT: Creating ordered metal-organic frameworks (MOFs) membranes with a scalable fabrication for continuous and homogeneous nanoarchitecture represent a category of tunable and functionalizable heterogeneous catalysts. In this work, we demonstrate a facile synthetic strategy for controlling Cu-MOF (1) to fabricate highly oriented MOF membranes (1a) with good controllability in membranes thickness on the macroporous Ni foam as the supporting scaffold, which can promote the growth of the uniform and high-quality MOF-based membranes with the benefit of readily accessible active sites. Nanoscale crystals of 1b also can be acquired by using surfactants as templates without Ni foam as surface-supported. Furthermore, MOFs-based 1-1b have indicated to be efficient heterogeneous catalysts to promote cascade indole acylation-Nazarov circularization for producing cyclopentenone[b]indoles skeletons. In particular, their unique membranes structure of 1a, containing ordered structure and molecular tunability, afford a well-defined platform to highly effective facilitate cyclization reactions by enhancing the diffusional rate and permeability with the minimum diffusion distance but does little for their selectivity. INTRODUCTION As the numerous heterogeneous catalysts utilized in industry, it is necessary to develop new-generation molecular catalysts on porous carrier which are suitable for industrial engineering.1,2 Metal-organic frameworks (MOFs), also called cellular materials which are made by metal coordination nodes and organic ligands, had demonstrated a multifunctional tunable hathpace to simulate these capabilities of natural enzymes and immobilize molecular catalysts for many important organic transformations.3-12 Although MOFs with uniformly dispersive isolated catalytic sites or synergistic catalysts have been examined, the catalytic property of MOFs is toujours restricted by the diffusion distances and rates of products and substrates in the cavities (pores) of the frameworks.13-28 To circumvent this problem and improve significantly catalytic active, it is central to relieve the diffusional constraint by decreasing single dimension (1D) of bulk MOFs samples to micrometer or nanometer in thickness to provide an interesting classification of highly ordered membranes materials, MOF-based membranes.29-33 Unlike three-dimensional (3D) MOF crystals, MOF-based membranes have large specific surface area promoting the touch of substrates with the readily accessible active centers on the membranes surface with minimal diffusion distance during the catalytic processes.29,30,34-37 On the other hand, MOF-based membranes inherit the high porosities, 2


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along with controllable channel sizes and functional active sites for maximum of the sieving effects and to construct well-defined multi-active platforms to increase the holistic penetrability of the membrane materials but does little for their highly selectivity.29,38-39 Moreover, highly ordered MOF-based membranes catalysts can realize precise control for fundamental structure-property investigations to simulate the active centers of numerous catalytic enzymes in nature.29,40-42 More important, MOF-based membranes also retain the heterogeneous characteristic, molecule functionality and tunability, and ordered structure of MOF catalysts, and have the possible to precise control of the catalytic microenvironments for the rational design and assembly of better solid catalysts to minimize the diffusional constrains.30,39,40,43,44 On the other side, our laboratory has paid close attention to develop MOF-based heterogeneous catalysts to execute tandem acylation-Nazarov cyclization reactions.45-47 It belongs to a class of acid-catalyzed acylation followed by 4π-electrocyclization to construct five-membered carbocycles for synthesizing of cyclopentenone frameworks, which are important intermediates in preparing numerous natural products, such as roseophilin, bruceolline E, taiwaniaquinol and so on.48-51 We recently showed that the Zn-MOF and Ag-MOF had displayed to be valable solid catalysts to facilitate cascade pyrrole dervatives cyclization reactions for producing cyclopenta[b]pyrrole skeletons.45,46 Inspired by preliminary results, we would like to explore MOFs-based catalysts for cascade indole derivatives circularization reactions for producing cyclopentenone[b]indoles skeletons. However, employing a series of Brønsted acids (such as TFA, HCl, or H3PO4), Lewis acids (such as BBr3, anhydrous AlCl3, SnCl4, anhydrous FeCl3, or ZnCl2), or MOFs (Ag-MOFs and Zn-MOFs) as homogeneous or heterogeneous catalysts usually produced no products or the acylation products with a modicum of the circularization products since indole had the lesser electron cloud density compared with that of pyrrole.52-57 Therefore, immobilizing of the high density of Lewis acidic active sites with continuous and ordered membranes utilizing a solid support to construct stable MOF-based membranes to simulate the complex characteristics of natural calssification for tandem reactions, can provide an interesting approach to afford the benefit of readily accessible active sites with minimum diffusion distance for the cascade indole circularization reaction for producing cyclopentenone[b]indoles skeletons. Herein, we demonstrate a strategy for the scalable fabrication of continuous and uniform nanoarchitecture MOF-based membranes on the macroporous substrate as catalysts to explore 3



cascade indole acylation-Nazarov circularization reactions. In order to acquire the benefit of readily accessible active sites in high-quality membranes, we incorporate a rigid and Y-shaped H3CPCDC ligand to link Cu2(COO)4 to construct a two-dimension (2D) layer structure [Cu(HCPCDC)H2O]n (1) with many large open channels. Then, highly oriented membranes (1a) with good controllability in membranes thickness were fabricated on the macroporous Ni foam as the supporting scaffold to facilitate their homogeneous and well-defined growth of MOF-based membranes. Nanoscale samples of 1b also can be obtained without Ni foam as surface-supported. Furthermore, we demonstrate the catalytic performances of MOFs-based 1-1b with regard to the cyclization to prepare cyclopentenone[b]indoles skeletons. This suggested that the catalytic performance of 1a was more effective than that of 1 and 1b, because of the homogeneous and continuous membranes, which can provide the tunable and functionalizable platform for the cyclization reaction by minimizing the diffusion distance and enhancing the diffusion rate but does little for their selectivity. As far as we know, until now, the cascade indole circularization reactions, which could be facilitated by the MOF-based membranes catalysts, have not been reported. EXPERIMENTAL SECTION Materials and Physical Measurements. H3CPCDC ligand and N-tosylindole were synthesized with the procedure modified from the literature.56,58 Ni foam was treated by 2M HCl, and then dried under vacuum oven overnight. The molarity of HNO3 was 16 mol/L. Other reagents were supplied by business purchase and utilized without distillation. A series of characterization, including 1H spectra, FT-IR spectra, Powder X-ray diffraction (PXRD), elemental analyses, X-ray photoelectron spectroscopy (XPS), thermal analyse, scanning electron microscopy (SEM), gas sorption isotherms, atomic absorption spectrum (AAS), inductively coupled plasma-atomic emission spectrometry (ICP-AES), and supercritical CO2 (SC-CO2) of complexes 1-1b were tested by series of instruments (Supporting Information). In addition, general process of cascade indole circularization reactions for 4a-f was provided in Supporting Information. Synthesis of [Cu(HCPCDC)H2O]n (1). Cu(NO3)2·3H2O (0.048 g), H3CPCDC (0.037 g), 2 mL H2O, 3 mL DMF and HNO3 (50 µL) were placed inside the bottle (10 mL). The bottle was aged 4 days under 85 °C, then blue rodlike samples of 1 were procured (yield, 62% depended on Cu). Analysis calculated (%) for C21H13CuNO7: C, 55.45 %; H, 2.88 %; N, 3.08 %. Found: C, 55.46 %; H, 4


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2.85 %; N, 3.10 %. IR: 3435 (vs)，2929 (vw), 1654 (w), 1607 (vs), 1511 (m), 1472 (w), 1389 (vs), 1234 (m), 1025 (vw), 920 (w), 780 (s), 724 (vw). Synthesis of MOFs-based membranes 1a on Ni foam. In a typical synthesis, Cu(NO3)2·3H2O (0.048 g) and PVP (0.2 g) were mixed in 2 mL H2O and stirred for 20 min in a 10 mL vial. The Ni foam was well immersed into the above solution and sonicated for 30 min. Subsequently, 3 mL DMF contained 0.1 mmol of H3CPCDC (0.037 g) and HNO3 (50 µL) were added and further sonicated for 1 hour. The mixture solution in the bottle was aged 4 days under 85 °C. After, the Ni foam was extracted, lined dry by H2O and EtOH, and dried under vacuum oven overnight. Synthesis of Nanocrystals 1b with PVP. In a typical synthesis, Cu(NO3)2·3H2O (0.048 g) and PVP (0.2 g) were mixed in 2 mL H2O and stirred for 20 min in a 10 mL vial until all PVP was dissolved. Subsequently, 3 mL DMF contained 0.1 mmol of H3CPCDC (0.037 g) and HNO3 (50 µL) were added and further sonicated for 1 hour. The mixture solution in the bottle was aged 4 days under 85 °C. After, the nanocrystals could be centrifuged at ten thousand rpm for fifteen minutes to transfer the supernatant. The nanocrystals were achieved, and further washed by EtOH (3×5 mL) and centrifuged at ten thousand rpm for fifteen minutes to isolate the crystal nanocrystals. Crystal Data Collection and Refinement. 1 was carried out by the Bruker D8 VENTURE diffractometer (λ = 0.71073 Å, Mo-Kα). The SAINT and SADABS program were used to control the restoring data and semiempirical absorption correction.59,60 The structure of 1 was worked out and refined by the SHELXL-1997 in Supporting Information.61 The detailed crystallographic data, bond lengths (Å), and angles (°) of 1 are afforded in Table S1 and Table S2, respectively (Supporting Information). The corresponding CCDC number is 1821724. RESULTS AND DISCUSSION Crystal structure. 1 crysalizes in the orthorhombic space group Pnna, and possesses a two-dimensional framework with the dimesions of the large open channels (25.27 ×16.14 Å2) (Figure 1a) (In view of van der Waals radii). In 1, the asymmetric unit includes one Cu2+ cations, one HCPCDC2- ligand and one coordinated water. Cu1 cations are binded with five O atoms (O1, O2, O5, O6, and O7) from one coordinated H2O and four HCPCDC2- ligands, respectively. Carboxylate groups build the plates of each variety of polyhedron and water molecules locate in the axial of acmes (Figure S1a). In 1, the two carboxyl groups in the H3CPCDC ligands are completly deprotonated and act as a 5



bismonodetate bridging linker to connect two Cu centers (Cu1 and Cu1a) with the Cu···Cu distance of 2.61 Å. Pairs of Cu2+ ions combine four carboxyl groups to give a {Cu2(COO)4} as the secondary building units (SBUs) (Figure S1b). Furthermore, these SBUs can be connected by carboxyl perssad of the HCPCDC2- ligands to provide a 2D layer structure, revealing a rhombus windows and a cavity suitable to put a sphere of 14 Å in diam (In view of van der Waals radii) (Figure S1c). Moreover, the 2D layers, stacked by π···π reciprocities with the adjacent carbazole rings (separation of 3.65 Å), give a supermolecule with an open architecture framework (Figure 1b). (Figure 1 here) Synthesis of controllable fabrication of MOFs-based membranes. Heterogeneous catalysts generally indicate morphology-dependent performaces, since the catalytic property rusts upon the diffusion rates and permeability of substrates and products within the surface of channels. The superiority of MOFs-based membranes as catalysts is that they keep well-organized structure, molecular controllaility and functionalization of MOF-based catalysts, and hold much promise for giving the well-defined platforms with readily accessible active sites in the membranes layer to increase the catalytic efficiency.30,39,40,62 Therefore, Ni foam, which was low cost and hig macroporsity, was used to develop a facile yet versatile approach, oriented surface-supported metal-organic frameworks (SURMOFs) controllable fabrication to in situ prepare MOF membranes with good controllability in membranes thickness (Figures 2a and 2b), because of its relatively low cost and high macroporosity. (Figure 2 here) By employing polyvinylpyrrolidone (PVP) as a surfactant, continuous and stabilized MOF-based membrane (1a) formed on the Ni foam (Figures 2c-d and Figure S2a). From the cross-section SEM images, it can be found that the membranes of 1a were uniformly anchored onto the Ni foam, and the membranes were well continuous growth with the thickness of approximately 500 nm (Figures 2e-f and Figure S2b). Clearly, energy dispersive spectrometry (EDS) and elemental mappings of the membranes of 1a further demonstrated the uniform and continuous distribution of the related elements (Cu, O, N, and C) in the membrane, displaying the homogenous growth of crystalline samples on the substrate (Figure S2c and Figure 3a). Moreover, ICP-AES analysis of the membranes of 1a revealed that only copper was found in the membranes, and XPS analysis indicated that their 6


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observation of Cu 2p3/2 peak at 934.67 eV demonstrated the CuII ions as the unique chemical states in 1a (Figure 3b). Moreover, PXRD study showed there were no remarkable variations among the datas of MOFs membranes, synthesis samples and simulated, which demonstrated that the crystal structures of the membranes and bulk samples kept unchanged (Figure S2d). In addition, without Ni foam as surface-supported, the sizes of 1 (~ 0.35 × 0.26 × 0.26 mm3, Figure S3a) can be minished to the nanometer dimension of about 300 nm in width by 1.0 µm in length at the same conditions, giving nanoscale crystals of 1b (Figures 3c-d and Figures S3b-c). PXRD analysis revealed that the nanoscale crystals of 1b excellently matched the simulated and synthesized PXRD patterns of bulk crystals 1 (Figure S3d), and the XPS spectrum of 1b indicated the posotions of Cu 2p3/2 at 934.78 eV, suggesting CuII ions as the single chemical states in 1b (Figure S3e). As the result, diverse morphologies and granular sizes of MOFs can be ascribed to the influence of the surface-supported. A Ni foam can be used to anchor copper cations on the carboxyl-group-terminated organic surface to provide a macroporous framework as the carrier to promote the growth of a well-proportioned and high-quality SUMOF membranes.24 In contrast, the growth of crystalline particles can be stemed by PVP as the capping agent that can not dominate the interactions between the MOF structure and the substrate in the absence of Ni foam. (Figure 3 here) Moreover, nitrogen sorption measurements of 1-1b after supercritical SC-CO2 activation displayed the N2 uptake of 156, 188, and 251 cm3g-1 at the saturated pressure, respectively (Figures S4a-c). According to the N2 adsorption isotherm, 1-1b possess the BET specific surface area of 585, 703, and 937 m2g-1, respectively. Derived from the N2 adsorption isotherm, it clearly demonstrated that the MOF-based membranes had the large BET surface areas to afford the benefit of readily accessible active centers for the cascade indole circularization reactions. In further studies, to study the effect of the concentrations of surfactant upon the formation of the thickness of membranes, many attempts for synthesizing crystalline 1a with various morphology and thickness were conducted by using PVP with different concentrations (0.3, 0.20, 0.15, 0.10, and 0.05 g) (Figures S4d-f). The results showed that well-defined morphology and thickness distributions of 1a could be obtained when the PVP concentration of 0.2 g. Thus, this research clarifies the property to regulate the functionalization of MOFs-based membranes with the same skeleton from the large scale to the 7



nanograde by developing Ni foam as surface-supported. The catalytic performance of 1a. To catalyze the cascade indole circularization reactions to prepare cyclopentenone[b]indoles skeletons, it is still a conundrum for delveloping new kinds of catalysts for controlling the highly efficient and selective Nazarov cyclizations to facilitate the muti-steps transformations. Encouraged by the high density of active sites in MOFs-based membranes, we were interested in probing whether an idea multiple active platform could be afforded by MOF membranes as catalysts for cascade indole circularization reactions to produce cyclopentenone[b]indoles skeletons as the single products. To convert these stoichiometric experiments for preparing cyclopentenone[b]indoles frameworks by cascade indole circularization reactions, the solvent resistance performance of 1a in DCE was preliminary tested by immersing the samples for 36 h in boiling DCE, because DCE was choosen as reaction solvent for this reaction. It was found that 1a had well solvent resistance performances, which could keep stable and remain original shapes boiling in DCE after 36 h. Besides, the thermogravimetric analysis (TGA) data was studied by inspecting the thermal stability of 1 (Figure S1e). Furthermore, we commenced optimization examines with N-tosylindole (2), TFAA, and crotonic acid (3a) as substrates for 3 h in different conditions (Table S3). After carefully massive testing of menstruums and temp, the optimal status was acquired in the existence of TFAA and 20 mol % of MOF membranes of 1a in DCM at 90 ºC for 3 h, providing the desired cyclopentenone[b]indoles frameworks (yield of 92%) via the tandem acylation-Nazarov cyclization process. Furthermore, attempts to substitute 1a with Ni foamed, 1, or 1b resulted in no or incomplete conversion of N-tosylindole and the cyclization product was given in yield of 0, 32 or 63%, respectively (Table S3, entries 15, 12 and 13). Moreover, the tandem acylation-Nazarov cyclization proceeded in poor to moderate yield in toluene (21%), DCM (39%), and CHCl3 (17%), but MeCN, THF, and Et2O were unsuitable solvents. For comparison, Cu(OTf)2 as homogeneous catalysts (Table S3, entry 14), which were usually used as homogeneous catalysts for this reaction, giving a few of cyclization products (21%). Therefore, it showed that 1a was highly efficient and selective catalyst to execute this reaction to produce cyclization products as the only products. In consideration of efficiency, selectivity, stability and simplicity, we identified 1a/TFAA/DCM/90 ºC as our optimal reaction conditions for this cyclization reactions. 8


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(Tables 1 here) Subsequently, the MOF-based membranes 1a catalytic methods was tested to be universal for promoting cyclization reaction with 3a-f and N-tosylindole (2) (Table 1). In all instances, heterogeneous catalyst 1a possesses excellent activity to facilitate these reactions, producing 4a-f with well and moderate selectivity for the cyclopentenone[b]indoles skelectons (yields, 86-92%). Moreover, when 1 or 1b was utilized as heterogeneous catalyst, the yileds of 4a-f were less than that of 1a as heterogeneous catalyst under uniform conditions, corresponding to the decrease of BTE surface area (1 < 1b < 1a). Furthermore, using 1, 1a and 1b as catalysts, the reaction gave the different conversion of N-tosylindole (2) during the reaction processes (Figure S5), which showed that the surface area played a vital role to infulence the diffusional rate in the reaction. To avoid the probability of the various activities of 3a-f resulting in such tendency, further experiments were implemented with the homogeneous catalysts (Cu(OTf)2, Table 1) under the same reaction conditions. Substrates 3a-f under the catalysis of Cu(OTf)2 provided a few of Nazarov cyclization products (yields, 16-21%), which do not match the decrease order of BTE surface area (1 < 1b < 1a). Furthermore, when the reaction time was extended 10h for 3f (bulky substrate) in the existence of 1 or 1b, the productivity risen from 39 to 84% or 53 to 87%, respectively (Table 1, entries 21 and 23). Thus, these results clearly indicated that an increase of the surface area leads to the increase in rate of reaction but has no influence on the selectivity. (Figure 4 here) The distinct and high catalytic performance of the present 1a system is attributed to spring from its picturesque structural characteristics and membranes materials. Structural study demonstrates that 1 includes the characteristic rhombus channel with the mesh size of 25.27 ×16.14 Å2 , which can act as a suitable space to promote the transport of organic substrates (3a: 5.80 × 3.07 Å2, 3b: 6.26 × 3.90 Å2, 3c, 6.19 × 4.09 Å2, 3d: 6.37 × 4.51 Å2, 3e: 8.75 × 3.83 Å2, 3f: 12.98 × 5.11 Å2) and products (4a-f). Moreover, SEM images show that the as-synthesized membranes of 1a with a thickness of approximate 500 nm, which possess the superiority of readily accessible active centers in the membranes to reduce the diffusion distance and enhance the products turnover and diffusion rates of substrates. The membrane of 1a is significant and display distinct substrate-catalyst interactions that can take advantage of regulating selectivity, synergistically increase the overall permeability of the 9



material to facilitate the tandem reactions and produce Nazarov cyclization products. Therefore, we hypothesized that the membranes of 1a can steady the intermeium provided in the circularization system and gave the tunable and functionalizable platform to execute cyclization in the large pores and demonstrate unique selective performance (Scheme S1). To certify the hypothesis, mapping experiments were utilized to explore the substrates and catalysts transformations. To acquire the changes of elements in the membranes, the various reaction processes (0 h, 1.5 h and 3 h) were elaborately regulated to research their reaction systems. The mapping images obviously display the distribution of Cu, N, O, C and S constituents during the reaction process (Figures 4a-c). The source of S element in the mapping images was ascribed to the N-tosylindole (2) utilized in the cyclization reaction. Moreover, considerable researches have been executed to explore the catalysts 1a with XPS (Figure 4d), aiming to demonstrate their tune of catalytic microenvironments of membranes 1a in various reaction times (0, 1.5, and 3 h). Therefore, the observation of Cu 2p3/2 peak at 934.59, 934.57, and 934.65 eV in XPS displayed that the valence state of Cu kept uniquely CuII during the reaction processes, which invariably retained the Lewis catalytic activity to facilitate cyclization reactions. In contrast, the low catalytic performance of 1 or 1b was ascribed to the particle sizes and BET surface areas, which not only limit the overall diffusional rates and diffusion distance, but also decrease the permeability of substrates and products transported in the channels. Therefore, emphasizing the advantage of membranes catalysts 1a over bulk crystals 1 or nanoscale crystals 1b as heterogeneous catalysts as diffusional constraints can be released. The heterogeneous feature of the membranes catalyst 1a was first verified by the filtration experiment. After 35% conversion of 2 in the presence of 1a for 1h, 1a was transfered by centrifugation and the mixture supernatant continue to work on for 2h. The result displayed that the conversion kept nearly unchanged in this period of time. Next, AAS analysis of the supernatant was examined at the end of the reaction. It was found that the existence of litte filtrating of Cu (< 1 ppm) from 1a was observed during the reaction. Thus, these consequences unambiguously revealed that 1a was truly heterogeneous catalyst. We have also evaluated the recyclability of heterogeneous 1a for the reaction with 2 and 3a. To conduct the recyclability experiments, 1a was carefully collected from the mixture by centrifugation, then the collected catalyst only slight deteriorated after ten runs (Figure S6a). Moreover, PXRD 10


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patterns and SEM images studies identified that the membranes catalyst 1a kept the same morphologies and frameworks after at least ten runs, which were possibly the reasons for the distinct catalytic performace and recyclability (Figures 6b-e). CONCLUSIONS In summary, we successfully revealed a moderate and versatile preparation strategy for the construction of SURMOF-derived nanoarchitecture membranes, in which the growth of well-proportioned and high-quality membranes can be anchored on macroporous Ni foam. The oriented nanoarchitecture membranes on the platform were proved to be able to accelerate the coring and the development of MOFs on the Ni foam, and importantly can regulate the continuous growth of crystalline samples in forming the membrane. Furthermore, with the benefit of readily accessible active centers in the MOF-based membranes, the membranes of 1a as a high performance heterogeneous catalyst to significantly outperform bulk crystals 1 or nanoscale crystals 1b to execute circularization with indole, give the tunable and functionalizable terrace for facilitating circularization by enhancing the diffusional rate and permeability with the minimum diffusion distance but does little for their selectivity. Supporting Information The detailed crystallographic data, bond lengths, angles of 1, TGA plots, PXRD patterns for 1-1b, details of results, and nitrogen isotherm data. These materials are available free of charge on the website. Corresponding Author *E-mail: [email protected] (H. Hou). *E-mail: [email protected] (C. H) *E-mail: [email protected] (L. M) Notes The authors declare no competing financial interest. Acknowledgments 11



The research was financially supported through the National Natural Science Foundation of China (Nos. 21701201, 21601212, 21671205, 21671174, and 21371155), the Key Natural Science Foundation of Henan Province, and the Scientific and technological project of Henan Province (182102210528). References (1) Satterfield, C. N. Heterogeneous catalysis in industrial practice, 2nd ed; McGraw-Hill: New York, 1991. (2) Norskov, J. K.; Bligaard, T.; Rossmeisl, J.; Christensen, C. H. Towards the computational design of solid catalysts. Nat. Chem. 2009, 1, 37-46. (3) Howarth, A. J.; Peters, A.W.; Vermeulen, N. A.; Wang, T. C.; Hupp, J. T.; Farha, O. K. Best Practices for the Synthesis, Activation, and Characterization of Metal-Organic Frameworks. Chem. Mater. 2016, 29, 26-39. (4) Zhao, M.; Yuan, K.; Wang, Y.; Li, G.; Guo, L.; Gu, L.; Hu, W.; Zhao, H.; Tang, Z. Metal-organic frameworks as selectivity regulators for hydrogenation reactions. Nature 2016, 539, 76-80. (5) Chughtai, A. H.; Ahmad, N.; Younus, H. A.; Laypkov, A.; Verpoort, F. Metal-organic frameworks: versatile heterogeneous catalysts for efficient catalytic organic transformations. Chem. Soc. Rev. 2015, 44, 6804-6849. (6) Sun, L.; Liu, X.; Zhou, H. Design and fabrication of mesoporous heterogeneous basic catalysts. Chem. Soc. Rev. 2015, 44, 5092-5147. (7) Zhang, T.; Lin, W. Metal-organic frameworks for artificial photosynthesis and photocatalysis. Chem. Soc. Rev. 2014, 43, 5982-5993. (8) Jiao, L.; Wang, Y.; Jiang, H.; Xu Q. Metal-Organic Frameworks as Platforms for Catalytic Applications. Adv. Mater. 2017, 29, 1703663. (9) Zhao, M.; Ou, S.; Wu, C. Porous Metal-Organic Frameworks for Heterogeneous Biomimetic Catalysis. Acc. Chem. Res. 2014, 47, 1199-1207. (10) Zhang, Y.; Shen, X.; Weng, L.; Jin, G. Octadecanuclear Macrocycles and Nonanuclear Bowl-Shaped Structures Based on Two Analog0ous Pyridyl-Substituted Imidazole-4,5-dicarboxylate Ligands. J. Am. Chem. Soc. 2014, 136, 15521-15524. (11) Lu, Y.; Deng, Y.; Lin, Y.; Han, Y.; Weng, L.; Li, Z.; Jin, G. Molecular Borromean Rings Based 12


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17



Figure 1. (a) View of the 2D framework of 1 with large open channels (25.27 × 16.14 Å2) along the b axis (considering van der Waals radii). Hydrogen atoms are omitted for clarity. (b) A space-filling view of the porous network along the b axis, showing the channels of 1.

18


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Figure 2. (a) Illustration of the synthesis process for the MOFs-based membranes catalysts. (b) A detailed SEM image of Ni form before deposition. (c, d) SEM images of MOFs-based membranes 1a on Ni foam with various magnifications. (e, f) Surface and cross-section SEM images of membranes 1a on Ni foam with various magnifications.

19



Figure 3. (a) Elemental mapping images of membranes 1a (b) XPS spectrum of 1a. (c, d) The morphologies and particle sizes of 1b induced by PVP with various magnifications.

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Table 1. MOFs-based 1-1b catalyzed tandem acylation-Nazarov cyclization for the synthesis of cyclopentenone[b]indoles.a

Entry

Catalysts

α,β-unsaturated carboxylic acids

1

1

Yield % of 4a-fb 51

2

1a

92

3

1b

63

4

Cu(OTf)2

21

5

1

48

6

1a

91

7

1b

60

8

Cu(OTf)2

20

9

1

48

10

1a

88

11

1b

58

12

Cu(OTf)2

18

13

1

44

14

1a

87

15

1b

55

16

Cu(OTf)2

17

Products

21



Page 22 of 24

17

1

43

18

1a

86

19

1b

55

20

Cu(OTf)2

16

21

1

39, 84c

22

1a

86

23

1b

53, 87c

24

Cu(OTf)2

16

a

Reaction conditions: N-tosylindole (1.0 mmol), α,β-unsaturated carboxylic acid (1.5 mmol), catalyst (0.20

mmol), TFAA (1.5 mmol), DCE (25 mL), reflux (3h). bIsolated yield of the product after 3h. cReflux (10h).

22


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Figure 4. (a) Elemental mapping images of 1a at the beginning (0 h). (b) Elemental mapping images of 1a with reacting 1.5 h. (c) Elemental mapping images of 1a at the end (3 h). (d) XPS spectrum of 1a during different reaction times (0, 1.5, and 3 h).

23



Page 24 of 24

For Table of Contents Use Only

Oriented

Controllable

Fabrication

of

Metal-Organic

Frameworks

Membranes as Catalysts for Tandem Indole Acylation-Nazarov Cyclization to Cyclopentenone[b]indoles Chao Huang,*,† Yingying Zhang,† Haiyan Yang,† Dandan Wang,† Liwei Mi,*,† Zhichao Shao,‡ Mengjia Liu‡ and Hongwei Hou*,‡

The continuous and uniform nanoarchitecture MOF-based membranes (1a) as a highly efficient heterogeneous catalyst was fabricated on porous Ni foam as the supporting scaffold to significantly outperform bulk crystals 1 or nanoscale crystals 1b to execute tandem acylation-Nazarov cyclization reaction with indole and α,β-unsaturated carboxylic acids.

24


Oriented Controllable Fabrication of MetalâOrganic Frameworks

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