2D MOFs and their derivatives for electrocatalytic applications: Recent advances and new challenges

Metal organic frameworks (MOFs) are promising electrocatalysts due to their high porosity, large specific surface area and adjustable structure. Especially, two-dimensional (2D) MOFs with ultra-thin structure provide more active sites and shorter diffusion distance for heterogeneous catalytic reactions. However, the poor conductivity and poor stability of 2D MOFs impede their practical electrocatalytic applications greatly. Therefore, 2D MOF-derived transition metal carbides, sulfides, phosphides, oxides, and single-atom catalysts have been fabricated by carbonization, vulcanization, phosphorization or oxidation strategies, which improve the conductivity and stability significantly. Here, the synthesis strategies of 2D MOFs and their derivatives are summarized, and the factors affecting the geometries and electronic structures of active sites are commented in detail. The electrocatalytic applications of 2D MOFs and their derivatives in oxygen evolution reaction (OER), hydrogen evolution reaction (HER), oxygen reduction reaction (ORR), carbon dioxide reduction reaction (CO2RR) and nitrogen reduction reaction (NRR) are reviewed. The effect of the geometric construction and electronic configuration of active sites (including metals, nonmetals, and defects) of 2D MOFs and their derivatives on the electrocatalytic performance is detailedly discussed by combining experimental achievements and theoretical analysis. Finally, the development prospects and challenges of 2D MOFs and their derivatives are proposed.