Highly selective photocatalytic CO2 reduction to ethane enabled by a tandem Au/UiO-68-NH2@MoS2 composite.

Solar-driven CO2 reduction to energy-dense C2 fuels remains challenging due to limited catalytic surfaces capable of sustaining both C-C coupling and full hydrogenation of intermediates in water. In this work, we report a tandem composite, Au/U68N(X)@MS, assembled from 3 wt% Au-preloaded UiO-68-NH2 (denoted as U68N) microcrystals and few-layer MoS2 nanosheets engineered with sulfur vacancies and dense Mo-edge ensembles. Under visible-light irradiation, Au/U68N motif serves as the photo-induced electron and CO-supply module, whereas vacancy-rich Mo sites on the edges of MoS2 chemisorb adjacent ∗CO intermediates, stabilize CO-CO-type dimers, and sustain subsequent multi-electron, proton-accessible hydrogenation steps that favor C2H6 formation over C1 product. Systematic modulation of the Au/U68N loading on MoS2 reveals that increasing the modification level progressively enhances interfacial conductivity and CO2 uptake capacity. In situ spectroscopic analyses further reveal a plasmon-enhanced Z-scheme charge-transfer pathway that preserves strong redox potentials across the heterointerface. Among the composites, Au/U68N(50)@MS delivers optimal tandem synergy, achieving a C2H6 productivity of 48.3 μmol h-1 g-1 with 72% selectivity. This outstanding performance positions Au/U68N(50)@MS among the most efficient photocatalytic CO2-reduction composites reported to date, highlighting that precise engineering of heterojunctioned composites is a decisive design parameter for steering aqueous CO2-to-C2 conversion.