Expanding Beyond the Micropore: Active-Site Engineering in Hierarchical Architectures for Beckmann Rearrangement

Abstract

The ability to engineer discrete solid-acid centers within hierarchically porous architectures that contain micropores with interconnected mesopores offers the potential to overcome the spatial restraints and diffusional limitations imposed by conventional microporous zeotype catalysts, which often lead to decreased catalyst lifetimes and restricted substrate scope. By employing a one-step soft-templating approach, coupled with detailed physicochemical and spectroscopic characterization, isolated, solid-acid sites can be suitably tailored and discretely modulated within the micropores and mesopores. The design strategy facilitates a synergistic enhancement in catalytic activity, selectivity, substrate versatility, and longevity, compared to analogous microporous zeotypes that have been extensively employed in the chemical industry, as solid-acid catalysts, for the production of e-caprolactam (precursor for Nylon-6).