Structure-Dependent Mechanisms of Visible Photolysis of Atmospheric Nitrophenols

Atmospheric nitrophenols (NPs) undergo visible-light-driven photolysis that significantly impacts reactive nitrogen cycling, yet their structural complexity hinders accurate impact assessment. Here, we reveal a structure-dependent photolysis mechanism of NPs adsorbed on photoactive particulate matter. The visible photolysis rates of representative NPs, such as J4-nitroguaiacol > J4-nitrocatechol > J5-nitrosalicylic acid, span 3 orders of magnitude, closely linked to the chemical reactivity of the nitro group (−NO2) site in NPs. The interfacial photochemistry process shows differential depletion of the −NO2 groups, consistent with their relative reactivities. Calculated average local ionization energy (ALIE) values serve as a predictive descriptor of visible photolysis potential, with lower ALIE correlating with faster photolysis. Validation across 10 atmospheric NPs supports the universal correlation between the visible photolysis rate and ALIE value, enabling prioritization of high-risk species and offering molecular-level insight into the photochemical transformation of complex organic pollutants.