Ligand-Channel-Engineered Ultrafast Charge Transfer in S-Scheme Heterojunction for CO ₂ Photoreduction Coupled with Biomass Valorization

Achieving photocatalytic conversion of CO2 coupled with 5-hydroxymethylfurfural (HMF) represents a highly forward-looking endeavor under the carbon neutrality context. This work innovatively constructs ligand-modified CdS quantum dots (QDs)-anchored on ZnCoNi-LDH nanocages (CdS/ZnCoNi-LDH) through a ligand-mediated interlayer anion exchange strategy. This strategy is demonstrated to exhibit universality for synthesizing composites comprising diverse ligand-functionalized CdS QDs and ZnCoNi-LDH with tunable interlayer anions. The efficient S-scheme charge separation and transfer mechanism is confirmed through in situ X-ray photoelectron spectroscopy, Kelvin probe and theoretical analysis. At molecular/atomic levels, femtosecond transient absorption spectroscopy elucidates the ultrafast charge transfer behavior through ligand-mediated interfacial channels in the CdS/ZnCoNi-LDH S-scheme heterojunction. In the CO2 reduction coupled with HMF oxidation system, CdS/ZnCoNi-LDH exhibits up to 16-fold and 41-fold enhancements in CO and 2,5-diformylfuran (DFF) yields, respectively, with selectivities exceeding 96% for CO and 93% for DFF. In situ experimental and theoretical results demonstrate that the redistribution of surface charges in CdS/ZnCoNi-LDH facilitates the adsorption of CO2 and HMF molecules, while simultaneously lowering the energy barrier for *CO desorption and hydroxymethyl dehydrogenation in HMF. This study provides an insight for synergistic utilization of CO2 and biomass valorization through engineered design of advanced S-scheme heterojunctions.