Catalytic testing. CO2 hydrogenation to methanol was conducted in a high-pressure continuous-flow fixed-bed reactor setup comprising mass flow controllers to feed gases (Bronkhorst, El-Flow F-201CV), pneumatic valves, a reactor with an inner diameter of 2.2 mm housed in an electrically-heated aluminum brass furnace, a pressure transducer, a burst plate calibrated at 6 MPa, a syringe pump to feed liquids (Chemyx Nexus 6000 Syring Pump), an online gas chromatograph (Agilent 7890 A equipped with Agilent DB-1 and GS-GasPro columns), and a computer control by a custom protocol within the LabView software. In a typical test, the reactor was loaded with 100 mg of the catalyst with a particle size of 100–125 μm, which was held in place by a bed of quartz wool and heated from ambient temperature to 553 K (5 K min−1) at 5 MPa under a He flow (20 cm3 min−1). After 3 h, the gas flow was switched to the reactant mixture (40 cm3 min−1) comprising H2 and CO2 (Messer, 99.997% and 99.999%, respectively) in a molar ratio of 4:1. For kinetic tests, temperature (473–653 K) and inlet partial pressures of reagents (pH2 = 3.5–4.5 MPa, pCO2 = 0.5–1.5 MPa) and products (pMeOH and pH2O = 0.05–0.25 MPa) were varied at a doubled WHSV attained by loading only 50 mg of catalyst diluted in 50 mg of TiO2 (100–125 μm, Sigma-Aldrich, > 99.9%). Water (ABCR-Chemicals, HPLC grade) or methanol (Sigma-Aldrich, > 99.9%, anhydrous) were fed to the reactor inlet by a high-pressure syringe pump (Chemyx Nexus 6000 Syring Pump). The effluent stream was sampled every 12 min and analyzed by on-line gas chromatography. Data evaluation procedures are presented in the Supplementary Methods and details to all catalytic tests are compiled in Supplementary Table 7.