Promoted hydrogenation of CO₂ to methanol over single-atom Cu sites with Na⁺-decorated microenvironment

Although single-atom Cu sites exhibit high efficiency in CO₂ hydrogenation to methanol, they are prone to forming Cu nanoparticles due to reduction and aggregation under reaction conditions, especially at high temperatures. Herein, single-atom Cu sites stabilized by adjacent Na⁺ ions have been successfully constructed within a metal-organic framework (MOF)-based catalyst, namely MOF-808-NaCu. It is found that the electrostatic interaction between the Na⁺ and H^δ- species plays a pivotal role in upholding the atomic dispersion of Cu in MOF-808-NaCu during CO₂ hydrogenation, even at temperatures of up to 275°C. This exceptional stabilization effect endows the catalyst with excellent activity (306 g·kg_cat^-1·h^-1), high selectivity to methanol (93%) and long-term stability at elevated reaction temperatures, far surpassing the counterpart in the absence of Na⁺ (denoted as MOF-808-Cu). This work develops an effective strategy for the fabrication of stable single-atom sites for advanced catalysis by creating an alkali-decorated microenvironment in close proximity.