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Hollow Zn-Co Based Zeolitic Imidazole Framework as Robust Heterogeneous Catalyst for Enhanced CO2 Chemical Fixation.

The efficient chemical conversion of carbon dioxide (CO 2 ) into value-added fine chemicals is an intriguing but challenging route in sustainable chemistry. Herein, hollow structured bimetallic zeolitic imidazole framework composed of Zn and Co as metal centers (H-ZnCo-ZIF) has been successfully prepared via a post-synthetic strategy based on controllable chemical-etching of the preformed solid ZnCo-ZIF in tannic acid. The creation of hollow cavities inside each monocrystalline ZIFs could be achieved without destroying the intrinsic frameworks, as characterized by field-emission scanning electron microscopy, transmission electron microscope, and X-ray diffraction technologies. The as-synthesized H-ZnCo-ZIF exhibited remarkable catalytic activity in the cycloaddition of CO 2 with epoxides to the corresponding cyclic carbonates, outperforming the solid ZnCo-ZIF analogue due to the improved mass transfer originated from the hollow structure. More importantly, due to stabilization of metal centers in ZIF framework by tannic acid shell, H-ZnCo-ZIF exhibited good recyclability and no activity loss could be observed in six runs. The present study provides a simple and effective strategy to enhance the catalytic performance of ZIFs by creating hollow structure via chemical-etching.