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.