Topotactic Synthesis and Photocatalytic Application of Metal Organic Framework (MOF)-Non-Stoichiometric Copper Sulfide (Cu2-xS) Nanocomposite Towards Activation of Atmospheric Molecules

Abstract

The rational construction of MOF-based n-p heterojunction via the in-situ topotactic method is an innovative approach to achieve efficient solar light harvesting for the conversion of atmospheric molecules to renewable energy and value-added chemicals. This study used solvothermal technique to synthesize a nonstoichiometric roxbyite (Cu58S32) phase with nanoplate (np) and snowflake (sf) morphologies by adjusting the types of sulfurizing agent. The nanohybrid Cu-BDC-NH2/Cu58S32 (CSM) was subsequently constructed in situ using the Cu58S32 (CS) as both a host matrix and a source of copper. Over the well-crystalline and radially symmetric hexagonal dendritic structure of CS(sf), Cu-BDC-NH2 MOF nanoplates grew a regulated pattern, resulting in the creation of an n−p heterojunction with a substantial interfacial contact area. Extensive characterization of the CSM nanohybrid materials demonstrated enhanced photon absorption, superior electrochemically active surface areas, and cooperative charge mobilization among the pristine semiconductor materials. Three different kinds of coordinated metal sites were observed in the surface-aligned ultrathin Cu-MOF nanosheets: monomeric Cu(II) with a distorted ligand environment and Cu(II) dimers with a paddle wheel-like structure. With reaction rates 14–20 times higher than pure semiconductors, the optimal CSM(sf) hybrid demonstrated enhanced photocatalytic activity toward H2 evolution (9343 μmolg−1h−1) and O2 reduction (2339 μmolg−1h−1) under solar light simulation. The significant surface hydrophilicity, distinct morphology, molecularly well-defined active sites as well as enhanced redox activity of photo-excited electrons by S-scheme charge transfer phenomena are crucial factors for the superior photocatalytic activity of CSM(sf) nano-hybrid1,2.