Nitrogen-Rich Tetrazole–Amide-Functionalised Zn Metal–Organic Framework as Catalyst for Efficient Catalytic CO2 Cycloaddition with Epoxides

Abstract

In this study, we report the design, synthesis, and catalytic application of the novel nitrogen-rich Zn(II) MOF [Zn2(μ3-1κN,2κN′,3κO-HL)2(DMF)2]n·nH2O (HL2− = 4-((4-(1H-tetrazol-5-yl)phenyl)carbamoyl)benzoate), denoted as ZnMOF, for the efficient conversion of carbon dioxide (CO2) to cyclic carbonates via cycloaddition with epoxides. It was synthesised from a tetrazole appended amide-functionalised pro-ligand (H3L) and Zn(NO3)2·6H2O under hydrothermal conditions. The synthesised material was characterised namely by elemental analysis, infrared spectroscopy, powder X-ray diffraction (PXRD), and single-crystal X-ray diffraction analyses. The catalytic potential of ZnMOF was investigated in the CO2 cycloaddition reaction with various epoxides, with conversions ranging from 17% to 99%. The catalyst retained its activity across multiple reaction cycles, demonstrating its stability and reusability. The influence of co-catalysts on the reaction was explored, with tetrabutylammonium bromide (TBABr) emerging as the most effective one. A plausible reaction mechanism is proposed.