Boxlike Assemblages of Few-Layer MoS2 Nanosheets with Edge Blockage for High-Efficiency Hydrogenation of CO2 to Methanol

Direct hydrogenation of CO2 into methanol is a promising strategy for reducing excessive dependence on fossil fuels and alleviating environmental concerns. Recently, in-plane sulfur vacancies in two-dimensional MoS2 nanosheets were unveiled as efficient catalytic active sites for methanol synthesis from CO2, whereas edge vacancies facilitated hydrogenation of CO2 to methane. Herein, we developed boxlike assemblages of quasi-single-layer MoS2 nanosheets, which were edge-blocked by ZnS crystallites (denoted as h-MoS2/ZnS) via a metal-organic framework (MOF)-engaged solvothermal route and subsequent heat treatments. The spatial confinement of the ZnS can restrain the growth and aggregation of MoS2 and ensure the stability of few-layer or even single-layer MoS2 in the assemblages. More importantly, the presence of ZnS can prevent reactants from approaching the edge sulfur vacancies of MoS2. With more exposed in-plane sulfur vacancies and less edge sulfur vacancies, the h-MoS2/ZnS exhibits 67.3% methanol selectively, 9.0% CO2 conversion, and a high methanol space-time yield of up to 0.93 gMeOH.gMoS(2-1).h(-1) at 260 degrees C, 5 MPa, and 15 000 mL.gcat(.-1).h(-1). The catalytic activity was stable for at least 120 h. By removing the ZnS phase from h-MoS2/ZnS and thus deliberately creating more edge sulfur vacancies, it was further confirmed that edge sulfur vacancies are active catalytic sites for excessive hydrogenation of CO2 to methane. Furthermore, the reaction mechanism of our catalyst was also investigated by a high-pressure in situ DRIFTS study. Thus, this MOF-templated strategy for assembling and confining quasi-single-layer MoS2 provides insights into the development of highly efficient transition-metal dichalcogenide catalysts for CO2 hydrogenation with excellent stability.

Automated summary

This study develops a new catalyst of box-like assemblies of quasi-single-layer MoS2 nanosheets, which effectively improves the selectivity for methanol synthesis and prevents excessive hydrogenation of CO2 to methane. The catalyst exhibits excellent catalytic activity and stability.