Triazine COF-supported single-atom catalyst (Pd1/trzn-COF) for CO oxidation

Single-atom catalysts (SACs) with well-defined and specific single-atom dispersion on supports offer great potential for achieving both high catalytic activity and selectivity. Covalent organic frameworks (COFs) with tailor-made crystalline structures and designable atomic composition is a class of promising supports for SACs. Herein, we have studied the binding sites and stability of Pd single atoms (SAs) dispersed on triazine COF (Pd-1/trzn-COF) and the reaction mechanism of CO oxidation using the density functional theory (DFT). By evaluating different adsorption sites, including the nucleophilic sp(2) C atoms, heteroatoms and the conjugated pi-electrons of aromatic ring and triazine, it is found that Pd SAs can stably combine with trzn-COF with a binding energy around -5.0 eV, and there are two co-existing dynamic Pd-1/trzn-COFs due to the adjacent binding sites on trzn-COF. The reaction activities of CO oxidation on Pd-1/trzn-COF can be regulated by the anion-pi interaction between a + delta phenyl center and the related -delta moieties as well as the electron-withdrawing feature of imine in the specific complexes. The Pd-1/trzn-COF catalyst is found to have a high catalytic activity for CO oxidation via a plausible tri-molecular Eley-Rideal (TER) reaction mechanism. This work provides insights into the d-pi interaction between Pd SAs and trzn-COF, and helps to better understand and design new SACs supported on COF nanomaterials.

Automated summary

Single-atom catalysts on covalent organic frameworks show potential for high catalytic activity. The study reveals that Pd single atoms can stably bind to triazine COF and exhibit high catalytic activity in CO oxidation reactions.