Aqueous microwave-assisted synthesis of non-interpenetrated metal-organic framework for room temperature cycloaddition of CO₂ and epoxides

다국어 초록 (Multilingual Abstract)

A multilinker non-interpenetrated metal-organic framework, UMCM-15, was synthesized by using microwave power as an alternative energy-efficient tool for the first time. The synergistic catalytic activity, when combined with a co-catalyst containing a strongly nucleophilic anion, was studied in the solventless room temperature cycloaddition between epoxides and CO<SUB>2</SUB>. Unlike previous reports on UMCM-15 synthesized in the high-boiling solvent dimethylformamide, low boiling water/ethanol mixture was used as the solvent herein. This approach holds potential as a sustainable green methodology. Crystal formation during the microwave-assisted (MW) synthesis was monitored at certain time intervals. The favorable role of non-interpenetrated pillared structures in promoting room temperature CO<SUB>2</SUB>-epoxide cycloaddition reactions was explained by comparing the catalytic efficiency of the three-linker extended pillar-layered non-interpenetrated UMCM-15 with its analogous pillared structures built from two- and three-fold interpenetrated ([Zn<SUB>2</SUB>(BDC)<SUB>2</SUB>(4,4'-bipy)] and [Zn<SUB>2</SUB>(NDC)<SUB>2</SUB>(4,4'-bipy)]) catalytic systems with a single dicarboxylate linker. The efficacy of the microwave-assisted UMCM-15(M) catalyst in cycloaddition reactions was proved by comparing the catalytic activity of UMCM-15(M) with that of the congener made by solvothermal synthesis, UMCM-15(S). In addition, a plausible mechanism for the synergistic operation of the Lewis acid sites and nucleophiles was suggested.