Enhanced hole–proton-coupled electron transfer of spin polarized photocatalyst via Mo–S4 coordination for sequential activation of C(sp3)–H and O–H bonds

Photocatalytic oxidative dehydrogenation of biomass feedstocks offers the possibility for synthesizing value-added chemicals, but the sluggish transport kinetics and rapid recombination of photogenerated charge carriers constrain photocatalysis efficiency. Spin-polarized photocatalysts, by accelerating the separation of photogenerated electrons and holes, offer a promising strategy for selective biomass valorization. Herein, polarization unit Mo was incorporated into ZnIn 2 S 4 (ZIS) with S-vacancy through Mo–S 4 coordination (Mo-Vs-ZIS) to enhance hole and proton-coupled electron transfer (PCET). Mo-Vs-ZIS spin polarized photocatalyst applied to 5-hydroxymethylfurfural (HMF) afforded a 2,5-diformylfuran (DFF) selectivity of 92.3% at a production rate of 1105.3 µmol g cat −1 h −1 , attributed to carrier transport and reaction processes. The Mo-Vs-ZIS photocatalyst efficiently (100 min) converted benzyl and furfuryl alcohols, aromatic alcohols bearing electron-rich substituents, and halogen-substituted aromatic alcohols into their corresponding aldehydes. Piezoelectric force microscopy (PFM) and Kelvin probe force microscopy analyses (KPFM) revealed that the full-space polarized electric field was formed to drive directional transfer of photogenerated carriers, facilitating bulk-to-surface charge separation. Moreover, Mo-Vs-ZIS showed high Bader charge transfer to O 2 , where Mo atomic sites functioned as an electron reservoir, driving the activation of O 2 to form •O 2 − , a kinetically favorable step for HMF oxidation and induced transfer of holes to activate C( sp 3 )–H bonds, which is a rate-determining step. Then, the critical step of PCET (•O 2 − +H + →•OOH) over Mo-Vs-ZIS gave •OOH for O–H activation to complete the reaction sequence. This spin-polarized modification strategy featuring atomic-level catalytic sites enables its application to other semiconductor photocatalysts for biomass conversion.