Solar-light-driven CO₂ reduction CO to CH₄ and C₂H₆ is a complex process involving multiple elementary reactions and energy barriers. Therefore, achieving high CH₄ activity and selectivity remains a significant challenge. Here, we integrate bifunctional Cu₂O and Cu-MOF (MOF = metal-organic framework) core–shell co-catalysts (Cu₂O@Cu-MOF) with semiconductor TiO₂. Experiments and theoretical calculations demonstrate that Cu₂O (Cu⁺ facilitates charge separation) and Cu-MOF (Cu²⁺ improves the CO₂ adsorption and activation) in the core–shell structure have a synergistic effect on photocatalytic CO₂ reduction, reducing the formation barrier of the key intermediate *COOH and *CHO. The photocatalyst exhibits high CH₄ yield (366.0 μmol·g⁻¹·h⁻¹), efficient electron transfer (3283 μmol·g⁻¹·h⁻¹) and hydrocarbon selectivity (95.5%), which represents the highest activity of Cu-MOF-based catalysts in photocatalytic CO₂ reduction reaction. This work provides a strategy for designing efficient photocatalysts from the perspective of precise regulation of components.

Semiconductors-based heterogeneous photocatalytic water splitting has been extensively studied, but it still remains challenging to accelerate the separation of electron–hole pairs and facilitate the reaction kinetics. Here we report a general strategy to fabricate highly efficient Pt/TiO₂ photocatalyst by coupling the Pt co-catalysts and surface oxygen vacancies (V_O) of TiO₂. TiO₂ was pre-modified with alkali or alkaline earth metals ion solutions, which produce a large number of surface hydroxyl on TiO₂. Subsequently, the photodeposited Pt sub-nanoparticles substitute surface hydroxyl and induce surface V_O on TiO₂. The coupling of Pt and surface V_O on TiO₂ can accelerate the extraction of photo-charges through the interaction of Pt–V_O–Ti bonds and reduce the hydrogen evolution barrier, thereby promoting the photocatalytic activity. The synthesized Pt-V_O-TiO₂ sample exhibits a photocatalytic hydrogen evolution activity as high as 1.5 L·g⁻¹·h⁻¹, which is 2.2 times that of traditional Pt/TiO₂. Our findings in-depth understand the synergistic effect of co-catalysts and defects on photocatalysis and open up new possibilities for achieving robust photocatalytic water splitting.