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

Abstract

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.