2D pyrene-based metal–organic framework nanobelts as efficient photocatalysts for the coupling of thiols into disulfides

Abstract

Photocatalytic coupling of thiols is a promising green approach to obtain disulfides. In this work, we report a stable pyrene-based MOF (Ni-PTTB) and its exfoliated two-dimensional (2D) nanobelts (Ni-PTTB-NB), which were prepared through the self-assembly of 1,3,6,8-tetrakis(3-carboxyphenyl) pyrene (H₄PTTB) and Ni(NO₃)₂·6H₂O. Taking advantages of the uniformly dispersed π-conjugated pyrene units, the obtained pyrene-based MOFs displayed visible-light absorption as well as intriguing optoelectronic properties. Interestingly, the 2D Ni-PTTB-NB showed obviously improved charge separation and migration compared to the pristine bulk Ni-PTTB, as revealed by a range of photoelectrochemical tests as well as Kelvin probe force microscopy (KPFM) measurements. Importantly, the Ni-PTTB-NB exhibited exceptional catalytic performance in the photocatalytic coupling of thiols in the air, giving rise to a 99% conversion of thiols and 99% selectivity of the disulfide products. Mechanism studies disclosed that the thiyl radicals are important intermediate in the catalytic process, which are obtained through the oxidation of thiols by the photogenerated holes. This work provides insights into the future design and development of 2D MOFs for the photocatalytic synthesis of high-value organic compounds.