Microenvironmental Tuning in Isostructural Conjugated Metal-Organic Frameworks for Superior Photocatalytic H2O2 Generation.

Photocatalytic hydrogen peroxide (H2O2) generation via sunlight-driven water and oxygen reduction reactions presents a sustainable alternative to the energy-intensive anthraquinone process. Although metal-organic frameworks (MOFs) offer tunable platforms for photocatalysis, the influence of metal-ligand microenvironment modulation within isostructural systems remains largely unexplored. In this work, we report two chemically robust conjugated 3D MOFs, Mn-Tp and Fe-Tp, synthesized via a scalable, solvent-free mechanochemical route and their exploration as photocatalysts. Despite sharing identical topologies and morphologies, Mn-Tp exhibits markedly superior photocatalytic performance, achieving a remarkable H2O2 yield of 10,487 µmol g-1 h-1, an apparent quantum yield of 9.94% at 467 nm, and a solar-to-chemical conversion efficiency of 0.45%. Mechanistic investigations, supported by theoretical calculations, reveal that subtle differences in the metal-node microenvironment modulate the electronic structure, promote dual-channel H2O2 generation via oxygen reduction and water oxidation, and suppress decomposition pathways. This study highlights the crucial role of local redox tuning in enhancing photocatalytic functionality, providing a strategic blueprint for designing next-generation MOF-based catalysts for the sustainable production of oxidants.