Highly-dispersed Pd nanoparticles on UiO-66 in assistance of supercritical fluid and its catalytic performance of CO2 methanation

Highly dispersed palladium nanoparticles (NPs) supported on UiO-66 as catalyst for CO2 methanation were prepared by supercritical fluid deposition (SFD). As a result, the most suitable Pd precursor salt and co-solvent are Na2PdCl4 and ethanol/DMF, respectively. The best SFD process condition to deposit the Pd precursor on UiO-66 is 40 °C, 10 MPa and 2 h. Under the above condition, 4% Pd/UiO-66 exhibits the highest activity with 53% of CO2 conversion and 95% of CH4 selectivity while the turnover frequency (TOF) value is 3669.4 h−1. The catalysts were characterized by XRD, BET, TEM, XPS, TGA, CO-DRIFTS and ICP-OES to investigate the structure–activity relationship. The 4% Pd/UiO-66 with the average size of 2.2 nm of Pd prepared in assistance of supercritical fluid behaved the similar activity as the 6%Pd/UiO-66 with average size of 9.7 nm of Pd prepared by sol–gel method. It is showed prospect of technique for reducing noble metal loading resulting from high dispersion effect.