Engineering Atomically Dispersed Cu Sites Confined in Hierarchical Silicalite-1@La ₂ O ₃ @Silicalite-1 Architecture for Spatiotemporal Decoupling of Bioethanol Upgrading

Bioethanol upgrading to higher alcohols (C4–10–OH) involves several sequential reaction steps occurring at multiple different active sites. Therefore, precisely engineering heterogeneous catalysts with appropriate local chemical structures of active sites and spatial environments is highly desired for efficient ethanol tandem conversion. Herein, we constructed a novel Cu-based catalyst featuring atomically dispersed Cu sites confined in a hierarchical silicalite-1@La2O3@silicalite-1 architecture, where single Cu atoms were confined in the micropores of surface silicalite-1 (S-1) zeolite nanoislands dispersed on the outer La2O3 layer encapsulating a hollow S-1 zeolite core. By modulating the content of Cu and La species, such a constructed multihierarchical Cu@S-1@La2O3@S-1 catalyst exhibited excellent performance in ethanol conversion to higher alcohols, along with an impressively high ethanol conversion of 74.9% and C4–10–OH selectivity of 85.0%, as well as an unprecedentedly high production rate of higher alcohols (10.575 mol·gCu–1·h–1) at 275 °C, far exceeding those over state-of-the-art Cu-based catalysts. It was elucidated that surface single-atom Cu sites first notably promoted the adsorption and activation of ethanol and thus initiated its dehydrogenation to produce acetaldehyde, and subsequently, acetaldehyde intermediates migrated to the outer La2O3 layer featuring abundant medium-strength basic and acidic sites, thereby facilitating the condensation of acetaldehydes and their further dehydration. This work provides an innovative approach for rationally designing high-performance supported Cu catalysts with a spatiotemporal decoupling structure applied in advanced heterogeneous tandem catalytic processes through the design of site-specific confinement within hierarchical structures.