Incorporation of Engineered Cu⁰/Cu⁺ Interfaces in Metal-Organic Frameworks for Boosting CO₂ Hydrogenation to Methanol

The Cu-based materials are an important category of catalysts for CO₂ hydrogenation to methanol, in which Cu⁰ and Cu⁺ species have been widely acknowledged to play key roles in the reaction. Herein, a series of metal-organic frameworks (MOFs), namely UiO-66(n) with exposed ─COOH groups, are fabricated by employing both terephthalic acid and 1,2,4-benzenetricarboxylic acid linkers. Following by introducing Cu nanoparticles, Cu@UiO-66(n) are synthesized. By regulating the amount of exposed ─COOH groups on the MOF pore wall, the interaction between Cu and the MOF support is regulated. This ─COOH microenvironment regulates the overall Cu⁰/Cu⁺ ratio in the supported Cu species, thereby tuning the Cu⁰/Cu⁺ interfacial descriptor, which is closely associated with the CO₂ hydrogenation performance. The Cu@UiO-66(25) featuring the longest Cu⁰/Cu⁺ interface achieves a methanol space-time yield of 694 g kg_cat ^-1 h^-1 and methanol selectivity of 92.8% at 250 °C and 4 MPa, far surpassing other counterparts. This work provides a deep understanding of the synergistic effect between Cu⁰ and Cu⁺ species in catalytic CO₂ hydrogenation.