Enhanced Oxidative Coupling of Thiols to Disulfides Using the Visible-Light-Responsive POM@MOF Constructed with Ru Metalloligands

The photocatalytic oxidative coupling of thiols to disulfides by using visible light represents an economically viable and environmentally sustainable strategy. A novel POM@MOF photocatalyst (Ru-CdS-SiW) was synthesized through the encapsulation of Keggin-type [SiW₁₂O₄₀]^4- within a MOF composed of Ru metalloligands and {Cd₄S₂O₁₆} clusters. In this structure, the incorporation of POMs to the MOFs reduced the charge transport distance, facilitated the separation and transfer of photogenerated charges and holes, and prevented the recombination of electron-hole pairs. The Ru-CdS-SiW catalyst demonstrated exceptional catalytic performance, achieving a 98.1% yield in the S-S bond formation from 4-methylthiophenol coupling with an apparent quantum yield of 4.8% at 440 nm. Through comprehensive exploratory experiments and electron paramagnetic resonance (EPR) measurements, we elucidated the mechanism underlying the photoinduced oxidative coupling of thiols. Notably, this catalytic reaction operates under mild visible-light conditions and exhibits remarkable recyclability, presenting significant potential for applications in sensitive systems, such as protein disulfide bond formation.