Dual-Functional Structure-Directing Agents Enable High-Loading Encapsulation of Ultrasmall Metal Nanoparticles in Zeolites

Abstract

Confined ultrasmall metal nanoparticles within zeolite crystals have emerged as promising catalysts due to their exceptional thermal stability and high catalytic activity under harsh reaction conditions. However, their loading amounts are limited to 1.0 mol % relative to SiO2, mainly due to steric hindrance and competition between metal species and structure-directing agents (SDAs) for access to micropores. Here, we introduce a molecular design strategy that unifies metal coordination and zeolite templating within a single dual-functional SDA molecule. This approach enables elevated metal loadings (up to ∼2.4 mol % relative to SiO2) of ultrasmall metal nanoparticles. This strategy is applicable to multiple microporous frameworks, including MFI zeolites and AFI aluminophosphate, allowing encapsulation of Cu, Co, and Pt nanoparticles. The metal encapsulation by microporous crystals renders them stable under harsh reaction conditions (e.g., high temperature) and thereby suppresses catalyst deactivation through sintering during the methane dry reforming reaction. We believe that our approach offers a molecular design principle for the synthesis of high-loading, sintering-resistant, zeolite-encapsulated catalysts.