PW12-M@COFs as efficient photocatalysts for visible-light-driven oxidation of various sulfides and degradation of chemical warfare agent simulant

From sustainable development and application standpoint, visible-light-driven oxidation of sulfides is emerging as sizzling focuses. In this work, a series of novel polyoxometalate-based photocatalysts, PW12-M@COFs 1 − 3 (M = Ag+ 1, Cu2+ 2, Ni2+ 3) were successfully synthesized via the electrostatic interactions between POM anion and cationic porous M@COFs, which were characterized by infrared (IR) spectroscopy, EDS analysis, solid diffuse reflective spectroscopy etc. These compounds exhibit strong visible light adsorption and can be used as excellent photocatalysts for the oxidation of sulfides to sulfoxides and the degradation of chemical warfare agent simulant, 2-chloroethyl ethyl sulfide (CEES). Especially, compound 1 with Ag+ has the best catalytic activity, achieving 98% of methyl phenyl sulfide conversion with 99% of selectivity in 3.5 h illuminated by a 10 W 425 nm light-emitting diode (LED). When extended to other sulfur-containing compounds, it also demonstrates satisfactory yield to sulfoxide and degrade CEES within 2 h. The mechanism reveals that both singlet oxygen and superoxide radicals act as the reactive oxygen species for the visible-light-driven oxidation of various sulfides, corresponding to the photoinduced electron-transfer and energy-transfer pathways. Moreover, these catalysts exhibited excellent catalytic and structural stability.