Leveraging phenazine and dihydrophenazine redox dynamics in conjugated microporous polymers for high-efficiency overall photosynthesis of hydrogen peroxide

Abstract

Harnessing solar energy for hydrogen peroxide (H₂O₂) production from water and oxygen is crucial for sustainable solar fuel generation. Conjugated microporous polymers (CMPs), with their vast structural versatility and extended π-conjugation, are promising photocatalysts for solar-driven H₂O₂ generation, though enhancing their efficiency is challenging. Inspired by the crucial role of phenazine derives in biological redox cycling and electron transfer processes, the redox-active phenazine moiety is rationally integrated into a CMP framework (TPE-PNZ). By leveraging the reversible redox dynamics between phenazine and dihydrophenazine, TPE-PNZ sets a new benchmark for H₂O₂ production among CMP-based photocatalysts, reaching a production rate of 5142 μmol g⁻¹ h⁻¹ and a solar-to-chemical conversion efficiency of 0.58% without requiring sacrificial agents. This interconversion allows for the storage of photogenerated electrons by phenazine and subsequent conversion into dihydrophenazine, which then reduces O₂ to H₂O₂ while reverting to phenazine, markedly facilitating charge transfer and mitigating charge recombination. Experimental and computational investigations further reveal that this reversible process enhances O₂ adsorption and reduction, significantly lowering the energy barrier towards H₂O₂ formation. This study offers critical insights into designing advanced materials for sustainable energy research.