Dimension and shape controllable ZIFs for highly-efficient chemical fixation of CO₂ without solvent and co-catalyst

The cycloaddition of CO₂ with epoxides is an important strategy to reach the goal of carbon neutral, at the same time high-value-added products can be obtained. The integration of Lewis acidic and alkaline sites makes ZIFs potential catalysts for the CO₂ cycloaddition. Herein, through simply adjusting the water proportion in the synthesis solvent, a series of ZIF materials were prepared and applied in the CO₂ cycloaddition. The transitional ZIF-(80)-Co combines the advantages of two-dimensional and three-dimensional ZIFs, namely the two-dimensional morphology, well-developed porous structures, higher CO₂ adsorption capacity, and rich acidic/alkaline sites. The outstanding microstructures and surface properties of ZIF-(80)-Co contribute to its superior catalytic performance for the CO₂ cycloaddition, and an epichlorohydrin (ECH) conversion of 96.9 % and a cyclic carbonate selectivity of 98 % are achieved without solvent and co-catalyst. Importantly, the cycloaddition of CO₂ with ECH over ZIF-(80)-Co is faster than most of the reported ZIFs in literature. Furthermore, ZIF-(80)-Co also exhibits excellent catalytic performance in the CO₂ cycloaddition with epoxy butane, allyl glycidyl ether, cyclohexene oxide and styrene oxide.