Efficient degradation of toluene over ultra-low Pd supported on UiO-66 and its functional materials: Reaction mechanism, water-resistance, and influence of SO2

Herein, Pd supported on UiO-66 as well as its NH2- and NO2-functional materials with ultra-low Pd loadings (0.05 ​wt%) were synthesized for toluene oxidation. Pd–U, using UiO-66 as the support, exhibited superb catalytic performance, water resistance, and resistance to SO2. A series of experiments and characterizations revealed that a high dispersion of small Pd clusters, high Pd0/Pdtotal proportion, better adsorption for toluene, and the best adsorption and activation capacities of gaseous oxygen species enhanced toluene degradation over Pd–U. Additionally, the catalytic mechanism over the Pd-based catalysts was revealed and discussed. Furthermore, the water-resistance and the SO2 concentration influence were tested and analyzed. Introducing H2O suppressed the adsorption and activation of toluene as well as gaseous oxygen species, and decreased catalytic performance over the three catalysts. The mechanism of the different impacts of SO2 on the three catalysts was investigated and elucidated. This study provides guidance for rationally designing catalysts for removing toluene under in-field operating conditions.