Enzyme-Inspired Design of Well-Defined Dual-Metal-Site Pairs Confined within Metal-Organic Frameworks for Tailoring...

Activity-selectivity trade-off remains a grand challenge and crucial issue in artificial photosynthesis. As for the natural enzyme system, bimetallic clusters confined in protein-folding chains enable regulating the activity-selectivity equilibrium for photosynthesis. However, current artificial photocatalysts lack the precisely synergistic control over active site configuration and catalytic microenvironments, causing the compromised trade-off between activity and specificity. Herein, we developed a "ship-in-bottle" strategy to confine well-defined dual-metal-site pairs (DMSPs) Co2L2 in the cage of amino-functionalized metal-organic framework UiO-67-(NH2)2, aiming at synergistic regulation of selectivity and activity for photocatalytic CO2 reduction. The as-synthesized Co2L2@UiO-67-(NH2)2 realized the highest syngas yield with CO/H2 ≈ 1/1, whereas only H2 but no CO was detected for original Co2L2. It was demonstrated that the tailored microenvironment around DMSPs enhanced the specific adsorption of CO2 like that in enzymes. Furthermore, the electron consumption rate of Co2L2@UiO-67-(NH2)2 (11078.00 μmol·gDMSP-1·h-1) was 63-fold higher than that of the Co2L2+UiO-67-(NH2)2 physical mixture counterpart (174.30 μmol·gDMSP-1·h-1), ascribing to the synergistic catalytic effect of DMSPs and improved charge transfer. As a proof of concept, this work integrates dual-metal-site catalysts with local microenvironment engineering to suppress the kinetically favored hydrogen evolution pathway and accelerate the CO2 reduction reaction process, providing a novel and feasible approach for optimizing artificial photosynthesis.