Green and high-yield synthesis of bimetallic zeolitic imidazolate framework-67 for efficient catalytic CO2 cycloaddition†

Metal–organic frameworks (MOFs) such as ZIF-67 have been widely studied. Incorporating multi-bimetals into ZIF-67 is a strategic approach to leverage unique properties and address the limitations of traditional single metals in ZIF-67. Herein, an environmentally friendly solid–solid thermal (SST) method is developed to simultaneously incorporate heterometals (Cu, Fe, Ru, Pd, Mn, and Ni) into the ZIF structure, referred to as M@ZIF-67. The synthesis occurs in a single step by utilizing thermally treated mixed solid precursors of multi-bimetals and imidazole ligands without additional agents or solvents, which is an innovative green route for preparing multi-bimetal ZIFs. Multiple techniques confirm that heterometals are homogeneously and uniformly distributed and have a precise metal content in the iso-structure of ZIF-67. Interestingly, synthesizing M@ZIF-67 through the SST method achieves a scalable and high yield. Furthermore, M@ZIF-67 exhibits a precise heterometal content, which plays a crucial role in enhancing its catalytic performance in CO₂ cycloaddition, surpassing results obtained using traditional ZIF-67.