Theoretical study on the selective adsorption, synergistic effects, and conversion of NO, NO2 and SO2 on Cug/PCN

Abstract

This study employs density functional theory calculations to investigate the adsorption and conversion mechanisms of typical flue gas components (NO, NO₂, and SO₂) on geminal-copper pair anchored polymeric carbon nitride (Cu_g/PCN). The results show that Cu_g/PCN exhibits significantly stronger adsorption of NO and NO₂ than SO₂. This high selectivity is primarily due to strong chemical bonding and substantial charge transfer between the Cu sites and NO/NO₂ species. A key finding is the quantitative confirmation of a significant attractive interaction (–ICOHP = 0.96 eV) between two co-adsorbed NO molecules, obtained via crystal orbital Hamiltonian population (COHP) analysis. This reveals a multi-molecular cooperative adsorption mechanism, which explains the exceptionally high adsorption strength of NO compared to predictions from single-molecule models. Furthermore, it provides a pre-activated configuration that facilitates subsequent efficient conversion of NO, such as the dimerization of 2NO to N₂O. Free energy calculations confirm that this conversion pathway is thermodynamically highly favorable. This research provides a theoretical basis for designing flue gas purification materials that integrate sensing and catalytic functions and underscores the critical role of cooperative adsorption in complex multi-molecular environments.