Synthesis of 2D nanoporous zeolitic imidazolate framework nanosheets for diverse applications

•2D zeolitic imidazolate framework (ZIF) nanosheets are widely studied and used.•2D ZIF nanosheets combine the features of ZIFs and the porous layer structure.•2D ZIF and 2D ZIF-derived nanosheets have been focused on in this review.•The challenges and perspectives of 2D ZIFs as nanoporous nanosheets are discussed. Two-dimensional (2D) zeolitic imidazolate framework (ZIF) nanosheets including ZIF-L, 2D ZIF-8/ZIF-67, 2D Ni/Cu-ZIF and M(Bim)(OAc)/M2(Bim)4 (M = Co, Zn; Bim = benzimidazole; OAc = acetate) have been used as nanoporous nanosheets in various applications. 2D ZIF nanosheets combine the desirable features of ZIFs and the porous layer structure, which give them some unique structure and chemical properties and superior performance over many other materials: the thin porous layer and the large external surface area facilitate the exposure of active sites and mass/ion/electron diffusion, and offer a beneficial environment for deposition of other nanomaterials. Additionally, the 2D morphology enriches the orientation arrangement and diversifies the alignment of pore channels, leading to the tight control on performance. By calcination or carbonization, 2D ZIF-derived materials can be obtained, which not only inherit the features of 2D ZIFs but also display new promising properties. In this review, 2D ZIF and 2D ZIF-derived nanosheets have been focused on, including the structure and morphology, intrinsic features, synthesis methods, modification/functionalization and applications. Furthermore, the current challenges and perspectives of 2D ZIFs as nanoporous nanosheets are discussed, aiming to give a thorough understanding of this area and promote the wide use of 2D ZIFs.