CO₂ Hydrogenation over Pt-Containing UiO-67 Zr-MOFs—The Base Case

Abstract

CO2 hydrogenation was carried out over Pt-containing UiO-67 Zr-MOFs at T = 220–280 °C and ambient pressure, with H2/CO2 = 0.2–9 and contact times, τ = 0.004–0.01 gcat·min·mL–1. The catalysts were characterized by XRD, N2 adsorption, FESEM, TEM and HRTEM, Pt L3-edge XANES and EXAFS, dissolution-NMR, CO chemisorption, IR spectroscopy, and TGA. A positive correlation was observed between the degree of Pt reduction and CO2 conversion. Contact time variation experiments showed that CO is a primary product of reaction, while CH4 is a secondary product. Testing of catalyst crystals with 0.15 and 2.0 μm crystal size, respectively, revealed no influence of diffusion on the reaction rate. Comparison to a conventional Pt/SiO2 catalyst showed very similar activation energy, with Eapp = 50 ± 3 kJ·mol–1. However, the turnover frequency over Pt/SiO2 was significantly lower, and Pt/SiO2 did not yield methane as a product. The Pt-containing UiO-67 Zr-MOF catalyst showed stable activity during 60 h of testing.