Silicalite-1 zeolite encapsulated Cu–ZnO nanoparticles for selective CO2 hydrogenation to oxygenates

Abstract

Selective conversion of CO₂ into value-added oxygenates, particularly methanol and dimethyl ether (DME), presents a promising route for CO₂ utilization. However, achieving both high selectivity and catalyst stability remained significant challenges. To address this, we report the fabrication of a core–shell-structured catalyst prepared by a steam-assisted crystallization (SAC) approach, in which highly dispersed Cu–ZnO nanoparticles (2.0–3.5 nm) are encapsulated within nanocrystalline silicalite-1 zeolite. The spatial confinement effects from silicalite-1 frameworks induce strong metal–zeolite interactions, effectively suppressing Cu–ZnO nanoparticle aggregation and sintering phenomena. This structural feature helps to preserve dominant populations of active Cu⁺ species on thermally stabilized Cu–ZnO nanoparticles. As a result, the optimized catalyst enables efficient tandem conversion of CO₂ to oxygenates, achieving a CO₂ conversion of 21.5% with an oxygenate selectivity of 83.0% toward dimethyl ether (DME, 72.5%) and methanol (10.5%), where an optimized catalyst exhibits exceptional catalytic performance for the tandem CO₂-to-DME reaction. Comprehensive characterization reveals that the spatial confinement within the protective silicalite-1 matrix not only stabilizes highly dispersed Cu–ZnO nanoparticles and Cu⁺ sites but also facilitates the formation and stabilization of key reaction intermediates. These synergistic effects are directly responsible for an enhanced catalytic activity, high DME selectivity, and prolonged operational durability observed during 300 h of continuous CO₂ hydrogenation.

Keywords: CO₂ hydrogenation; Encapsulation; Silicalite-1 zeolite; Cu–ZnO nanoparticles; Oxygenates.