Tailoring surface reaction pathways by self-assembling a trifluoromethyl-terminated molecular layer to enhance photocatalytic cellulose-to-syngas conversion in pure water†

Photocatalytic cellulose conversion offers a sustainable route for syngas production by utilizing solar energy and renewable biomass, in comparison with conventional syngas production that primarily relies on non-renewable fossil resources. However, its efficiency in pure aqueous systems remains limited due to uncontrolled deep oxidation toward CO₂. Herein, we report a trifluoromethyl-terminated hole-selective molecular layer (Poz3F) engineered onto ZnSe@TiO₂ heterojunctions to regulate interfacial reaction mechanisms. Mechanistic studies reveal that the Poz3F layer suppresses hydroxyl radical formation, facilitates hole accumulation on the heterojunction surface, and steers glucose reforming pathways through altering the adsorption configuration. This dual modulation promotes decarbonylation of aldehydes and dehydration of formic acid, activating direct CO generation while suppressing CO₂ formation. The heterojunction with optimized Poz3F coverage achieves high syngas evolution rates of 2061, 1775, and 1276 μmol g⁻¹ h⁻¹ for glycerol, glucose, and α-cellulose, respectively, with CO/CO₂ selectivity enhancements of 1.84-, 3.15-, and 3.44-fold compared to the unmodified counterpart in pure water. Remarkably, stable syngas production over 100 hours is realized with glucose, alongside successful application with respect to raw biomass substrates of wood, grass, and paper in pure water. This work establishes molecular-level surface engineering as an effective strategy to synchronously enhance activity and selectivity in solar-driven biomass-to-syngas conversion.