Atypical Hybrid Metal–Organic Frameworks (MOFs): A Combinative Process for MOF-on-MOF Growth, Etching, and Structure Transformation

The structural, compositional, and morphological features of metal–organic frameworks (MOFs) govern their properties and applications. Construction of hybrid MOFs with complicated structures, components, or morphologies is significant for the development of well-organized MOFs. An advanced route is reported for construction of atypical hybrid MOFs with unique morphologies and complicated components: 1) MOF-on-MOF growth of a 3D zeolitic imidazolate framework (ZIF) on a ZIF-L template, 2) etching of a part of the 2D ZIF-L template, and 3) structural transformation of 2D ZIF-L into 3D ZIF. The formation of core–shell-type MOF rings and plates is controlled by regulating the three processes. The formation route for the core–shell-type MOF rings and plates was monitored by tracking changes in morphology, structure, and composition. Carbon materials prepared from the pyrolysis of the core–shell-type hybrid MOFs displayed enhanced oxygen reduction reaction activities compared to their monomeric counterparts.