Modulating the Selectivity of CO₂ Photoreduction by Regulating the Location of PtCu in a UiO-66@ZnIn₂S₄ Core–Shell Nanoreactor

Controlling product selectivity in CO2 photoreduction remains a grand challenge, particularly when CH3OH is the targeted product. Herein, we demonstrate a strategy for tuning the selectivity of core–shell-structured UiO-66@ZnIn2S4 (UiO/ZIS) in visible-light-driven catalytic reduction of CO2 by regulating the location of PtCu cocatalysts. The PtCu nanoparticles are confined within the inner UiO-66 core to afford PtCu/UiO/ZIS, incorporated at the UiO-66/ZnIn2S4 heterointerface to form UiO/PtCu/ZIS, and anchored on the outer ZnIn2S4 surface to fabricate UiO/ZIS/PtCu. The primary CO2 reduction products for PtCu/UiO/ZIS, UiO/PtCu/ZIS, and UiO/ZIS/PtCu are CO, CH3OH, and CH4, with selectivities of 52.1, 72.7, and 88.8%, respectively. Experimental and theoretical results demonstrate that the spatial position of PtCu affects both the charge separation efficiency and the H2O oxidation rate in the ternary photocatalysts. This, in turn, influences the supply of electrons and protons to the active sites, leading to varying degrees of CO2 hydrogenation and deoxygenation. Additionally, different PtCu positions also create distinct reactive sites and surrounding microenvironments, altering the energy barriers of key reaction steps and giving rise to diverse CO2 reduction pathways. This work provides fresh hints for rationally controlling product selectivity in artificial photosynthesis through the precise regulation of cocatalyst placement within heterostructured photocatalysts.