Efficient Photosynthesis of Hydrogen Peroxide from Water and Air over Water-Dispersible Anthraquinone-Based Porous Aromatic Frameworks

Abstract

Photosynthesis of hydrogen peroxide from earth-abundant water and air over organo-based semiconducting materials is a promising alternative to the traditional anthraquinone (AQ) method. However, the generally hydrophobic nature of organic semiconductors has led to their poor dispersibilities in aqueous systems, which built huge barriers for photon capture and reactant contact in water-based photocatalysis. Aiming at this issue, this study reports the facile synthesis of AQ-based porous aromatic frameworks (AQ-PAFs) by coupling of AQ fragments with thiophene-derived linkers via robust carbon-carbon bonds. Remarkably, the interfacial hydrogen bonding interactions between water molecules and AQ sites on the surface improves the general hydrophilicity of AQ-PAFs, which can be well-dispersed in water only systems with uniform particle size distributions. Moreover, the AQ moieties also function as mediators of photoinduced electrons, and the protons produced from water oxidation reaction (WOR), which would kinetically favor the charge separation and subsequent electron transfer reactions. The mono-dispersed AQ-PAF photocatalyst promotes H2O2 photosynthesis from water and air under visible light achieving a high productivity of 7124 μmol g–1 h–1 in the absence of any organic alcohol reagents, among organic semiconductor photocatalysts. Furthermore, a continuous H2O2 photosynthesis for 190 hours is also achieved in a flow system.