Ethylene Methoxycarbonylation over Heterogeneous Pt 1 /MoS 2 Single-Atom Catalyst: Metal-Support Concerted Catalysis.

Ethylene methoxycarbonylation (EMC) to methyl propanoate (MP) is an industrially important reaction and commercially uses a homogeneous Pd-phosphine organometallic complex as the catalyst and corrosive strong acid as the promoter. In this work, we develop a Pt 1 /MoS 2 heterogeneous single-atom catalyst (SAC) which exhibits high activity, selectivity, and good recyclability for EMC reaction without need of any liquid acid. The production rate of MP achieves 0.35 g MP g cat -1 h -1 with MP selectivity of 91.1% at 1 MPa CO, 1 MPa C 2 H 4 , and 160 °C, which can be doubled at 2 MPa CO and corresponds to 320.1 mol MP mol Pt -1 h -1 , at least 1 order of magnitude higher than the earlier reported heterogeneous catalyst and even comparable to some of homogeneous catalyst. Advanced characterizations and DFT calculations reveal that all the Pt single atoms are located at the Mo vacancies along the Mo edge of the MoS 2 nanosheets, forming pocket-like Mo-S-Pt 1 -S-Mo ensembles with uniform and well-defined structure. Methanol is first adsorbed and dissociated on Mo sites, and the produced H spillovers to the adjacent Pt site forming Pt-H species which then activate ethylene, forming Pt-ethyl species. Meanwhile, CO adsorbed on the other Mo site reacts with the Pt-ethyl species, yielding propionyl species, and this carbonylation is the rate-determining step. The final methoxylation step proceeds via the nucleophilic attack of propionyl species by -OCH 3 affording the final product MP. Such a metal-support concerted catalysis enabled by the Mo-S-Pt 1 -S-Mo multisite ensemble opens a new avenue for SACs to promote the multimolecular reactions that prevail in homogeneous catalysis.