Precise Dual-Metal Pairs Enable Ultrafast Structural Response for CO₂-to-Ethylene Photoconversion

Dual-metal sites have shown great potential for high catalytic performance, owing to their synergistic effects. However, randomly distributed dual-metal sites and unidentified coordination environments make it challenging to investigate charge transfer dynamics and elucidate actual catalytic mechanisms. Herein, we report a judicious strategy to construct precisely distributed dual-metal pairs through anchoring single atoms in vacancy-rich metal-organic frameworks (MOFs), enabling ultrafast structural response for CO₂ photoreduction to ethylene. Using oxygen vacancy-rich Mil-125(Ti)-NH₂ loaded with Cu atoms as an example, low-dose real-space imaging and X-ray absorption spectra reveal the well-defined distribution of Cu-Ti dual-metal pairs, resulting in rapid charge transfer from Ti to neighboring Cu within 3.0 ps. Remarkably, a high solar-to-chemical efficiency of 0.62% with a superior electron-based selectivity of 78.3% for ethylene production from CO₂ and H₂O is achieved. Mechanistic investigation unveils that the unique Cu-Ti bimetallic pairs induce strong d-p hybridization with *CHOCO intermediates and undergo structural self-regulation under excitation, thereby facilitating C-C coupling to proceed spontaneously. The generality of precise dual-metal pairs for the ethylene synthesis is also realized by other MOF-based catalysts. This work enlightens a meticulous strategy to attain identified dual-metal catalytic sites and bridges the discrepancy between experimental study and theoretical insight.