Desulfurization of Mercaptobenzimidazole and Thioguanine on Gold Nanoparticles Using Sodium Borohydride in Water at Room Temperature

Organosulfur compounds are known to poison metallic nanoparticle catalysts. Herein NaBH 4 is shown to desorb and desulfurize 2-mercaptobenzimidazole (2-MBI) and 6-thioguanine (6-TG) adsorbed on 10, 15, and 50 nm diameter gold nanoparticles (AuNPs). The desulfurization rates decrease significantly with increasing AuNP sizes. Isotope labeling experiments, conducted with NaBD 4 in H 2 O, indicate that this desulfurization reaction proceeds through a pathway requiring hydrogen uptake onto AuNP surfaces prior to the 2-MBI or 6-TG desulfurization reaction, rather than direct hydride attack from BH 4 – on the sulfur-bearing carbon in 2-MBI or 6-TG, or H 2 reaction with 2-MBI or 6-TG . In addition to serving as the hub for electron charge transfer between hydride and proton, AuNPs capture the cleaved sulfide, facilitating sulfur separation from the desulfurized products.