Nanocomposites comprising metal nanoparticles (MNPs) anchored on hollow framework (MNP-on-HF) surfaces demonstrate versatile applications across multiple disciplines. Notably, leveraging the molecular sieving effect of support layer pore sizes in NP-loaded catalysts enables enhanced selectivity in heterogeneous catalytic reactions. Nevertheless, such composites often suffer from limited catalytic efficiency due to reactant diffusion constraints within the HF cores. To address this challenge and improve the selectivity of multireaction competition, we propose a novel polymer-coated strategy to synthesize a series of MNP-on-HF catalysts for efficient hydrogenation. By precisely modulating the size of the inner core during encapsulation, we synthesized Co-on-HF catalysts with tunable pore sizes (50-750 nm), which can manage the adsorption of nitro compounds, further confining the formation of catalytic products with high selectivity. The nitrogen-doped surfaces of these Co-on-HF composites achieved superior nitrobenzene hydrogenation conversion rates compared to nonpolymer-coated analogues, while simultaneously demonstrating remarkable size selectivity through the molecular sieving effect of their tailored pore architectures. This pore size control enables the selective production of aniline, azobenzene, or azobenzene oxide from nitrobenzene hydrogenation. Importantly, this synthetic methodology can be extended to diverse active site-HF combinations, underscoring its broad potential for the design of advanced catalysts with precisely controlled reactivity and selectivity profiles.
Shi et al. (Tue,) studied this question.