CO2 hydrogenation on Cu-catalysts generated from ZnII single-sites: Enhanced CH3OH selectivity compared to Cu/ZnO/Al2O3

• Cu-Zn/SiO 2 based heterogeneous catalyst for CO 2 reduction via surface organometallic chemistry. • Small and narrowly distributed CuZn x nanoparticles. • Reversible alloying-dealloying process. • Improved MeOH selectivity. • Formation of Zn II and CuZn x by in situ XAS. The hydrogenation of CO 2 to CH 3 OH is mostly performed by a catalyst consisting mainly of copper and zinc (Cu/ZnO/Al 2 O 3 ). Here, Cu-Zn based catalysts are generated using surface organometallic chemistry (SOMC) starting from a material consisting of isolated Zn II surface sites dispersed on SiO 2 – Zn II @SiO 2 . Grafting of [Cu(OtBu)] 4 on the surface silanols available on Zn II @SiO 2 followed by reduction at 500 °C under H 2 generates CuZn x alloy nanoparticles with remaining Zn II sites according to X-ray absorption spectroscopy (XAS). This Cu-Zn/SiO 2 material displays high catalytic activity and methanol selectivity, in particular at higher conversion compared to benchmark Cu/ZnO/Al 2 O 3 and most other catalysts. In situ XAS shows that CuZn x alloy is partially converted into Cu(0) and Zn(II) under reaction conditions, while ex situ solid state nuclear magnetic resonance and infrared spectroscopic studies only indicate the presence of methoxy species and no formate intermediates are detected, in contrast to most Cu-based catalysts. The absence of formate species is consistent with the higher methanol selectivity as recently found for the related Cu-Ga/SiO 2 .