Spatially Separated Redox Centers in Anthraquinone-grafted Metal-Organic Frameworks for Efficient Piezo-photocatalytic H2O2 Production

Piezo-photocatalytic production of hydrogen peroxide (H2O2) from water and air is promising but its large-scale application is still challenging as insufficient reaction active sites and low reaction efficiency. We have applied molecular engineering methods to design an anthraquinone molecularly (AQ) grafted metal-organic framework piezo-photocatalyst (UiO-66-AQ) for H2O2 generation from water and air. The catalyst achieves a peak H2O2 yield of 7872.4 mu M g(-1) h(-1) by facilitating two critical reactions: single-electron water oxidation (WOR) and two-electron oxygen reduction (ORR) on spatially separated redox sites. Experiments and computational simulations reveal efficient charge separation through a ligand-to-chain transfer mechanism. Electrons and holes are selectively transferred to AQ and UiO-66 promoting ORR and WOR under ultrasound and visible light. The high reaction rate of ORR (rapid generation of endoperoxide) compensates for the slow kinetics of WOR (generation of OH*) and greatly increases the rate of full-reaction of H2O2 production. Additionally, a continuous flow tubular reactor equipped with UiO-66-AQ catalytic membranes affords 96 % removal of organic dyes by a in situFenton process under visible light and water flow, confirming the significant potential of the catalyst for practical applications. This work deepens the understanding of directional carrier migration at piezo-photocatalytic spatial separation sites, opening new pathways for environmentally friendly and efficient H2O2 synthesis.