Pd ₄ S Nanoparticles on Sulfur‐Rich Hollow Carbons: Controlled Catalysts for Semi‐Hydrogenation of Alkynes Even with Extended Reaction Times

This work presents the development of an efficient new catalyst based on microporous organic polymer (MOP) chemistry for the selective semi-hydrogenation of terminal alkynes to alkenes. Various Pd-based coupling reactions are employed in MOP synthesis. Hollow MOPs (H-MOPs) are prepared through the Glaser coupling of 1,3,5-triethynylbenzene using 60 mol% (PPh₃)₂PdCl₂, utilizing silica nanospheres as templates. The Pd catalysts are entrapped into the MOP networks. Post-synthetic modification with sulfur leads to the creation of sulfur-rich (23 wt.% sulfur) materials (H-SMOPs). Subsequent heat-treatment of H-SMOPs under argon results in the formation of Pd₄S nanoparticles on hollow carbon supports enriched with 16 wt.% sulfur. The resulting H-SC@Pd₄S catalyst demonstrates excellent selectivity for the semi-hydrogenation of both aryl and aliphatic terminal alkynes to styrenes (93-99%) and aliphatic alkenes (96-98%), respectively, maintaining the high selectivity for alkenes even with further extended reaction times of 6-16 h. Moreover, H-SC@Pd₄S displays excellent recyclability over five consecutive runs, maintaining yields and selectivity.