Sulfur-Promoted Hydrocarboxylation of Olefins on Heterogeneous Single-Rh-Site Catalysts br

Sulfur poisoning is a severe problem in industrialapplications, attracting broad interest in fundamental research studies.Although a number of studies about sulfur resistance have beenimplemented in many reactions on nanoparticle catalysts, fewinvestigations focus on carbonylation reactions using heterogeneoussingle-metal-site catalysts (HSMSCs). Herein, we present anunanticipated sulfur-promoted performance in olefin hydrocarbox-ylation reactions on a single-Rh-site catalyst supported on porousionic polymers (Rh1/PIPs) with 1000 ppm H2S in CO feed.Ex situEXAFS andin situDRIFTS revealed a ternary cycle mechanism ofolefin hydrocarboxylation reactions with Rh-Hcomplexesaspredominant active species in both pure and H2S-containingfeedstock. Moreover, the transformation of the Rh mononuclear complex with the addition of H2S was also demonstrated.Density functional theory studies were performed to verify the feasibility of the proposed pathway and confirm that the energybarriers of transition states with the sulfur ligand were much lower than those in normal feed, for example, a decline of 3.4 kcal/molfor the rate-determining step of migration and insertion of CO. This work provides a distinctive example for the insight of sulfureffect on carbonylation, which could be potentially beneficial for further applications of HSMSCs.