In Situ Exfoliation of Covalent Metal-Organic Frameworks for Enhancing Photocatalytic Hydrogen Peroxide Production

Two-dimensional nanosheets exhibit largely enhanced photocatalytic activities for hydrogen peroxide (H₂O₂) production. Conventionally, the nanosheets are fabricated through ex situ approaches (i.e., top-down and bottom-up) prior to catalytic applications. However, the preparation of 2D MOF nanosheets via in situ exfoliation remains largely unexplored. Herein, we report the synthesis of three 2D silver cyclic trinuclear unit (Ag-CTU)-based covalent metal-organic frameworks (CMOFs). Owing to their excellent light adsorption ability and suitable bandgap, these CMOFs can serve as efficient photocatalysts for synthesis of hydrogen peroxide (H₂O₂) from water and oxygen. Notably, the H₂O₂ production rates of these CMOFs were increased continuously during the photocatalytic processes, reaching 0.50, 1.40, 2.88, and 3.60 mmol g^-1 h^-1 after 6, 18, 36, and 72 h, respectively. Mechanistic studies reveal that in situ exfoliation of these CMOFs into ultrathin nanosheets (∼0.87 nm) significantly enhances their photocatalytic activity. Moreover, these CMOFs achieve a remarkable H₂O₂ accumulation of 609 mM over 72 h, to best of our knowledge, which surpasses the most previously reported values.