Ultrafast Photocatalytic Decontamination of Mustard Gas Simulant and Thermodynamic Insights by a Metal-Free Imidazoline Porous Organic Polymer

Detoxification of mustard gas through selective partial oxidation to sulfoxide is efficient yet challenging due to the hazardous nature of the overoxidized sulfone product. Metal-free imidazoline-based POPs, an emerging class of efficient photosensitizers with excellent chemical stability, incorporate both electron-rich and electron-deficient units with donor–acceptor junctions. In this study, we developed a highly photoactive protonated imidazoline-based POP, IPM-401, illustrating mild oxidizing power and enhanced ROS generation capability. Toward the detoxification of mustard gas simulant 2-chloroethyl ethyl sulfide (CEES), IPM-401 displayed excellent performance with ultrafast kinetics of t_1/2 = 4.9 min in O₂-saturated and t_1/2 = 5.7 min under aerobic atmosphere, respectively, utilizing MeOH as the suitable solvent system. Additionally, ITC analysis revealed a favorable thermodynamic interaction (ΔG = −6.39 kcal/mol) between IPM-401 and CEES. Density functional theory calculations further validated this interaction, confirming the favorable binding of CEES to the imidazoline moiety of IPM-401. The underlying detoxification mechanism in different solvent systems is further advocated by experimental data. IPM-401 also demonstrates its versatile photocatalytic activity toward sulfide and aromatic aldehyde oxidation reactions across a broad range of substrates. Furthermore, the practical relevance of chemically stable IPM-401 was also established from its satisfactory recyclability performance up to 10 cycles.