Mechanistic Insights into the Atomic Distance Effect on Adsorption and Degradation of Aromatic Compounds

Atomic-level dispersed metal–N–C frameworks are considered effective materials for the catalytic oxidation of aromatic pollutants by modulating the electronic structures of atomic metal centers. However, the inherent electronic mechanism for the influence of varying anchoring atomic distances on the enrichment and further degradation of aromatic compounds is unclear. Herein, covalent triazine frameworks (CTFs) anchored by Ni single atoms (Ni-SA/CTF), Ni clusters (Ni-AC/CTF), and NiO nanoparticles (NiO-NP/CTF) were successfully constructed as reaction platforms. The results showed that Ni-AC/CTF exhibited the highest adsorption capacity (624.4 μmol g–1) for 2,2′,4,4′-tetrahydroxybenzophenone (BP-2) and the fastest reaction kinetics (3.01 h–1) for rhodamine B (RhB). The experiments and theoretical calculations further revealed that the interaction between Ni atoms in the atomic clusters in Ni-AC/CTF shortens the Ni–N bonds and weakens the asymmetric spin state. These changes cause benzene ring distortion in pollutant molecules, further promoting the ring cleavage reaction and improving electron delocalization and transport, which synergistically enhance the aromatic pollutant removal performance. This study explains the advantages of atomic cluster catalysts in the activation and degradation of aromatic pollutants at the electronic level, providing a direction for the development of advanced photocatalytic materials.