Optimizing the Interfacial Environment of Triphasic ZnO-Cu-ZrO2 Confined inside Mesoporous Silica Spheres for Enhancing CO2 Hydrogenation to Methanol

Achieving the desired catalytic activity and selectivity in CO2 hydrogenation to methanol remains a grand challenge using nonprecious metals. Herein, the well-known ternary Cu-ZnO-ZrO2 (CZZ) was spatially sequestered as fine, uniformly dispersed active interfaces onto an engineered mesoporous silica sphere (MSS), giving rise to Cu-ZnO-ZrO2/MSS (CZZ-MSS) with confined binary Cu-ZnO/ Cu-ZrO2 and ternary interfaces that fostered methanol production under moderate conditions (30 bar and 200-280 degrees C). By systematically investigating the CZZ-MSS performance, we show that spatial confine-ment and optimization of the interfacial environment of the catalytically active interfaces inside well-fabricated mesoporous silica deliver a markedly enhanced specific methanol yield (2211 gMEOH-kgCu-1-h-1) compared to conventional supported catalysts including an industrial catalyst (368 gMEOH-kgCu-1-h-1) and a vast majority of reported catalysts. Besides, the strong metal-support interaction arising from interacting metallic Cu and metal oxides (ZnO and ZrO2) within the confined, ultrasmall nanoparticles (<3.0 nm) demotes the sintering of Cu NPs while retaining their H2 dissociation strength, resulting in superior and prolonged catalytic stability over 100 h. In situ DRIFTS of confined catalysts with monophasic, biphasic, and triphasic interfaces expectedly suggests the occurrence of different CO2 hydrogenation reaction paths over triphasic Cu-ZnO-ZrO2/MSS (formate pathway) compared to monophasic Cu/MSS (reverse water-gas shift (RWGS) pathway) and biphasic ZnO-ZrO2/MSS. From the appreciable insights gained herein, the rational support synthesis bringing the confinement effect to the robust ZnO-Cu-ZrO2 interface is the rationale behind the higher rate of methanol synthesis observed in the CO2 hydrogenation.