Surface Hydroxyl Steered Adsorption Configuration for Efficient Photocatalysis Coupling Hydrogen Evolution and 5-Hydroxymethylfurfural Selective Oxidation Toward 2,5-Furandicarboxylic Acid Production.

Photocatalytic coupling water reduction reaction and 5-hydroxymethylfurfural (HMF) selective oxidation toward 2,5-furandicarboxylic acid (FDCA) offers a promising route for co-production of green hydrogen and value-added bio-based platform chemicals, but limited by low FDCA selectivity and yield. Herein, an Al-doped SrTiO3 (STO) photocatalyst integrated with RhCrOx and Co3O4 cocatalysts is investigated for HMF oxidation reaction (HMFOR) under neutral and alkaline conditions. While alkaline conditions markedly improve the FDCA production, the accelerated HMF self-degradation and competing Cannizzaro side-reaction compromise the hole utilization efficiency. Spectral and theoretical investigations reveal that surface-bonded hydroxyl (─OH) species on Co3O4 under alkaline conditions steer HMF adsorption from vertical to a tilted configuration, which facilitates the rate-determining step of 5-hydroxymethyl-2-furancarboxylic acid (HMFCA) to 5-formyl-2-furancarboxylic acid (FFCA) conversion. Building upon this mechanistic insight, Co3O4 is substituted with a ─OH terminated Co(OH)2 oxidation cocatalyst, which sustains the favorable flat HMF adsorption configuration even under neutral and oxygen-free conditions. The obtained RhCrOx/STO/Co(OH)2 achieves a FDCA selectivity of 72.7% and a yield of 49.0% for HMFOR, together with hydrogen evolution rate of 626 µmol g-1 h-1. This study demonstrates that steering reactant adsorption configuration via surface ─OH species offers an effective strategy for efficient solar-driven photocatalysis coupling biomass valorization and hydrogen production.