Construction of Single-Cluster Rhodium Catalyst for Efficient CO₂ Hydrogenation to Ethanol

Thermocatalytic conversion of carbon dioxide (CO₂) into ethanol is a promising strategy for efficient utilization of CO₂. However, it remains a grand challenge to achieve a high ethanol yield due to the difficulty in accurate control of CO₂ activation and C-C coupling under thermocatalytic reaction conditions. Herein, a precise rhodium (Rh) single-cluster catalyst on carbon nitride support (Rh_SC/CN) was designed for CO₂ hydrogenation to ethanol. The Rh_SC/CN catalyst, with an average Rh-Rh coordination number of 2.06, exhibits a record turnover frequency (TOF_Rh) of 595.2 h^-1, a high ethanol selectivity of 95.3% and an ethanol yield of 17.5 mmol g_cat ^-1 h^-1 at 240 °C and 5.0 MPa (H₂/CO₂ = 3), surpassing previously reported Rh-based catalysts. Density functional theory calculations, in situ diffuse reflectance infrared Fourier transform spectroscopy, X-ray absorption spectroscopy and H₂/D₂ isotope exchange probing experiments altogether reveal the reaction mechanism, and show that the synergetic interaction between Rh-Rh and Rh-N sites boosts CO₂ adsorption and asymmetric C-C coupling between CH₃* and CO* to form CH₃CO*, leading to a high ethanol selectivity. This discovery provides new insights into the design of single-cluster catalysts for simultaneously promoting CO₂ reactivity and ethanol selectivity.