Synthesis of metal-organic framework microrings via an anisotropic growth-etching approach

Design of metal-organic frameworks (MOFs) with elaborate structural features is of great significance for their applications with improved performances. In this work, we report the construction of unique zinc-based zeolite imidazole framework (ZIF-8) microrings via an anisotropic growth-etching route. The synthesis relies on the anisotropic deposition of ZIF-8 crystals on the edges with coordinatively unsaturated Zn²⁺ of leaf-like ZIF (ZIF-L) nanosheets and subsequent selective etching of alkaline unstable ZIF-L. Furthermore, functional carbon materials with a ring-like structure can be prepared by pyrolysis of ZIF-8 microrings as precursors, exhibiting enhanced oxygen reduction reaction performance compared to the traditional ZIF-8 derived counterparts. Our work may pave the way for the design of MOFs with sophisticated micro/nanostructures.