Efficient Solvent‐Free Carbon Dioxide Fixation Reactions with Epoxides Under Mild Conditions by Mixed‐Ligand Zinc(II) Metal–Organic Frameworks

Parth Patel; Bhavesh Parmar; Rukhsana I. Kureshy; Noor‐ul Khan; Eringathodi Suresh

Index: 10.1002/cctc.201800137

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Abstract

Mixed‐ligand 3 D/2 D Zn metal–organic frameworks (MOFs) {[Zn(bdc)(L1)]⋅x G}n (ZnMOF‐1) and {[Zn(ipa)(L2)]}n (ZnMOF‐2; in which H2BDC=benzene‐1,4‐dicarboxylic acid, L1=4‐pyridyl carboxaldehyde isonicotinoylhydrazone, H2IPA=isophthalic acid, L2=3‐pyridyl carboxaldehyde nicotinoyl hydrazone, and G=lattice guests) were synthesized using versatile synthetic routes that include a green mechanochemical (grinding) reaction. Chemical and thermal stability, phase purity, and characterization of the ZnMOFs synthesized by different approaches were established by using various analytical methods. Both ZnMOFs can be used as a highly active, solvent‐free, binary catalyst for CO2 cycloaddition with epoxides under ambient reaction conditions of 1 atm pressure and room temperature/40 °C, in the presence of the cocatalyst nBu4NBr. The yield, recyclability, and stability of ZnMOF‐1 as a potential catalyst towards epoxide to cyclic carbonate conversion are excellent under ambient conditions. From literature and experimental inferences, a rationalized mechanism mediated by the Zn center of ZnMOFs for the CO2‐epoxide cycloaddition reaction has been proposed. To the best of our knowledge, very few MOF‐based catalysts have been reported to realize the conversion of CO2 to useful products under similar mild conditions. In the present investigation, that is, catalyst preparation by green mechanochemical synthesis and catalysis under ambient, solvent‐free conditions were performed with minimum energy utilization.