Mechanism-Guided Design of Metal–Organic Framework Composites for Selective Photooxidation of a Mustard Gas Simulant under Solvent-Free Conditions

Photoactive metal–organic frameworks (MOFs) and their derivatives have shown great promise for the degradation of mustard gas and its simulants (e.g., 2-chloroethyl ethyl sulfide or CEES) by selectively oxidizing these toxic organic sulfides to less toxic sulfoxide products under visible or ultraviolet (UV) light. However, these reactions must be conducted in specific solvents (e.g., methanol) to achieve satisfactory selectivity of sulfoxide, which limits the use of MOFs in protective gears. Our mechanistic study shows that during the photooxidation of CEES, the stabilization of a putative persulfoxide intermediate with hydrogen-bond donors was crucial for the formation of sulfoxide. Based on this discovery, we developed a series of MOF/textile composites containing various hydrogen-bond donor additives for selective photooxidation of organic sulfides under solvent-free conditions. With a 3 mol % catalyst loading, our best-performing composite degraded all CEES within 15 min in oxygen under blue LEDs without solvents, featuring a reaction half-life of 4.4 min and a sulfoxide selectivity of 91%. Under the same condition, the pristine MOF-525 powders only converted 30% CEES after 15 min and showed a 58% sulfoxide selectivity in the final products. Remarkably, this composite also achieved rapid, selective, and solvent-free degradation of CEES utilizing air and simulated sunlight with excellent stability and reusability. This work demonstrates that selective photooxidation of organic sulfides can be achieved without organic solvents under near-practical conditions. The MOF textile composites developed here can be potentially implemented in protective masks and suits against mustard gas.