Fabricating bimetallic single clusters into porphyrinic metal-organic frameworks for CO₂ reduction to methanol via hydrosilylation

As a new kind of potential catalysts containing both maximum atom efficiency and high synergetic effect, heteronuclear metal single clusters (SCs) with metal–metal bonds have been successfully anchored into porphyrinic metal-organic frameworks, giving rise to a series of MOF composites named after Ir_xCu_1−x-SCs@Co-PCN-222-PyzA. Among them, Ir_0.15Cu_0.85-SCs@Co-PCN-222-PyzA displayed the highest efficiency and accelerated the selective reduction of CO₂ to methanol via hydrosilylation under 15% CO₂ pressure with the turnover frequency of 356 h⁻¹ and turnover number of 2453 based on the Ir content. Ir_0.15Cu_0.85-SCs@Co-PCN-222-PyzA could be recycled and reused for 10 successive runs with no loss of the reactivity and selectivity. Mechanistic studies revealed that the superior reactivity might be attributed to “co-adsorption–co-activation” of reaction substrates by the bimetallic single clusters of Ir_xCu_1−x-SCs within the confined nanospaces of Co-PCN-222.