Boosting toluene oxidation by the regulation of Pd species on UiO-66: Synergistic effect of Pd species

Supported single-atoms and sub-nanometre clusters have exhibited superb catalytic performance toward many reactions. However, inactivation of single-atom or cluster catalysts in complex reactive conditions poses major challenge for their practical application. Herein, we demonstrate that the prepared Pd-UiO-66 with ultra-low Pd loading (0.05 wt%) contains three robust active Pd species, (isolated Pd atom (Pd1), sub-nanometre Pd clusters (Pdc) and Pd nanoparticles (Pdn)) and presents superb activity for toluene oxidation and water resistance (10.0 vol%). Experiments and theoretical calculations firstly confirm that con-secutive H-2-O-2 and reaction gas treatment (1000 ppm toluene in 20 vol.%O-2/Ar) induce residual N species from solvent N, N-dimethylformamide to enter UiO-66 skeleton forming Pd1-N1 structures. DFT calculations reveal that the synergistic effect of Pd species (namely, the enhanced activation of O-2 and H2O by Pd1 and the improved adsorption of toluene by Pdc and Pdn) is the main factor for the excellent activity of Pd-U-H-O-reused catalyst. (C) 2022 Elsevier Inc. All rights reserved.