Hollow carbon sphere nanoreactor decorated with uniformly dispersed Cu nanoparticles: Tunable interfacial electronic structures for enhanced nitroarene reduction

An efficient catalytic hydrogenation of nitroarenes into their derived anilines is of critical importance for fine chemicals industry and environmental remediation. Herein, a Cu decorated hollow carbon nanosphere (Cu/<em>h</em>-CS) was demonstrated as a promising nanoreactor to achieve enhanced hydrogenation toward nitroarene reduction. The unique hollow configuration of <em>h</em>-CS provided sufficient binding sites for Cu anchoring on interior and exterior surfaces, effectively preventing Cu agglomeration. The resulting homogenously dispersed Cu nanoparticles on <em>h</em>-CS exhibited a strong electronic interaction at the interface, leading to the generation of favorable electrophilic Cu^δ+ sites. Meanwhile, thin shells with nanoporous channels enabled rapid electron migration, and regulated the mass transfer to boost reactant enrichment due to the void-confinement effect. Compared with its counterpart of Cu loaded solid carbon nanosphere (Cu/<em>s</em>-CS), the desirable structural and electronic configurations of Cu/<em>h</em>-CS offered a preferable micro-environment to achieve markedly enhanced catalytic activity in hydrogenation reactions. As an exemplary verification, the Cu/<em>h</em>-CS demonstrated a high turnover frequency of 740.74 h^-1 for 4-nitrophenol reduction (~3-fold that of Cu/<em>s</em>-CS), an impressive reduction applicability toward a series of nitroarenes and azo-dyes, as well as an acceptable stability after 10 catalytic cycles. This work sheds new light on the design and construction of low-cost and high-performance catalysts for wide hydrogenation applications.