TEMPO-mediated selective oxidation of organic sulfides with atmospheric oxygen over the NU-1000 photocatalyst

Metal–organic frameworks (MOFs) are crystalline porous materials constituted of metal–oxo nodes and multitopic organic linkers, which have emerged as promising visible light photocatalysts. Herein, NU-1000, a MOF constructed from Zr 6 O 8 cluster node and 4,4′,4′′,4′′′-(pyrene-1,3,6,8-tetrayl)tetrabenzoic acid organic linker, serves as a photocatalyst for the selective oxidation of organic sulfides with atmospheric oxygen (O 2 ). Notably, the TEMPO (2,2,6,6-tetramethylpiperidine- N -oxyl)-mediated hole transfer significantly enhances the oxidation reaction. TEMPO not only suppresses electron–hole recombination but also facilitates charge transfer to organic sulfides. Remarkably, the incorporation of TEMPO (3 mol%) approximately doubles the conversions of thioanisoles compared to NU-1000 alone under blue light irradiation. Furthermore, electron paramagnetic resonance (EPR) spectroscopy tracks the transmutations of TEMPO into an EPR-inactive species and O 2 into superoxide resulting from hole and electron transfers over the NU-1000 photocatalyst under blue light irradiation. NU-1000 and TEMPO enable the selective generation of organic sulfoxides from diverse thioanisoles with O 2 . This work lays the groundwork for the future development of MOFs as effective photocatalysts via mediated electron transfer.