Rational design of zero-valence and well-dispersed copper nanocluster stabilized by carbon-coated SiO2 for highly effective and ultrafast reduction of nitroarenes

In this work, we present a ligand modification strategy that allows for the regulation of the valence and dispersion state of Cu clusters in the final obtained Cu@C/SiO₂ catalyst. Specifically, the phthalic acid (PA) ligand promotes the uniform anchoring of zero-valence Cu nanoclusters on Cu@C/SiO₂, resulting in excellent catalytic activity in the selective reduction of toxic 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) with a rate constant (k) of 19.06×10^-3 s^-1. This value was approximately 2.4- and 31.2-fold higher than that of the CuO/SiO₂ and bare CuO catalysts, respectively. Additionally, no significant decline in activity was detected during six successful cycles. Through systematic analysis of structural and electronic properties of the catalyst, we confirmed that the coordination effect of the PA ligand and the carbothermic effect of its carbon derivatives effectively prevent particle aggregation and modulate the valence state of copper species in Cu@C/SiO₂, resulting in superior catalytic performance.