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 °C). By systematically investigating the CZZ-MSS performance, we show that spatial confinement and optimization of the interfacial environment of the catalytically active interfaces inside well-fabricated mesoporous silica deliver a markedly enhanced specific methanol yield (2211 g_MEOH·kg_Cu^-1·h^-1) compared to conventional supported catalysts including an industrial catalyst (368 g_MEOH·kg_Cu^-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.