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/Pd_total 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.