Synergistic thermal-mass enrichment on macro-mesoporous N,S-codoped carbon derived from used tea for ultrafast nitroaromatics reduction

Nitroaromatic reduction is one of the most valuable industrial reactions; however, the development of eco-friendly carbon-based metal-free catalysts is extremely limited by their low activities and insufficient wettability. Herein, we present a highly efficient hierarchical macro-mesoporous N,S-codoped carbon catalyst, derived from used tea featuring a superhydrophilic structure achieved through an alkaline-mediated thiourea activation carbonization strategy, for the reduction of nitroaromatic compounds. The ultrahigh-carbon macroporous structure is crucial for maximizing the exposure of the external surface area of active sites. Additionally, N,S-codoping enhances surface wettability, ensuring excellent accessibility of active sites in aqueous reactions. These outstanding advantages enable the optimized catalyst (N,S₁-TC-600) to exhibit high catalytic activity in nitroaromatic reduction. Finite element method and density functional theory calculations indicate that N and S codoping within the macroporous structure results in superior catalytic performance through the synergistic effect of thermal accumulation and mass transfer enrichment on the macro-mesoporous carbon catalyst, which is driven by redistribution of charge and spin density. Furthermore, activation energy barrier calculations revealed that the optimized N,S₁-TC-600 has a lower activation energy for 4-nitrophenol reduction. This work presents a valuable methodology for constructing and modulating the electronic state of highly efficient carbon-based metal-free catalysts, which may provide a general guidance for the fabrication of other carbon-based catalysts.