Optimizing Electronic Topology of Curvature-Induced Cu–N ₂ Asymmetric Structure for Maximized Cu Utilization in CH ₃ SH Photo-oxidation

The highly symmetrical M-N₄ structure with dispersed atoms exhibits a symmetric charge distribution, which leads to strong binding with adsorbed molecules but reduces active site accessibility and limits electron utilization. Herein, the curvature effect of carbon nitride nanotubes (CNNTs) was employed to modulate the geometric and electronic topologies of curved Cu-N₂ asymmetric motifs. Surface stress induced the formation of unique "Cu protuberance" on CNNT, resulting in a maximum Cu atom dispersion of 5.66%, 13.8 times higher than that of the planar Cu-melon structure (0.41%). Additionally, the Cu-N₂ site acts as a reservoir for electrons, enhancing the accessibility of Cu sites. This improved electronic interaction with CH₃SH decreased electron occupancy in the Cu 3d antibonding orbital and induced unconventional d-p hybridization between Cu and S atoms, thereby improving CH₃SH photo-oxidation efficiency. Consequently, Cu-CNNT-400 with the optimal curvature radius exhibited the highest CH₃SH removal efficiency (90.4%), demonstrating a volcano-like relationship between catalytic activity and nanotube diameter. Importantly, maximizing Cu atom utilization can effectively reduce the required amount of Cu precursors and lower catalyst costs. This study provides valuable insights into precise catalyst design for maximizing metal atom utilization in gaseous contaminant removal.