Manipulating the Coordination Structure of Biomass-Derived Zinc Single-Atom Sites to Boost Selective Catalytic Hydrogenation of Nitroarenes

Constructing highly efficient and stable non-noble metal catalysts for selective hydrogenation of nitroarenes is a very appealing yet challenging task in the fields of materials science and catalysis. Herein, a series of N-doped carbon-anchored Zn single-atom catalysts were prepared by pyrolyzing the biomass-based composite precursors composed of chitosan, tannic acid, and ZnCl 2 . The optimal sample of Zn-Cl/NC-3_900 displays superior catalytic activity with a turnover frequency of 4817 h −1 at 80°C, selectivity (∼99%), and recyclability (without any post-treatment) for hydrogenation of p -chloronitrobenzene to p -chloroaniline with N 2 H 4 ·H 2 O. Its catalytic performance is well kept even after HCl or KSCN treatments, revealing excellent chemical stability and anti-poisoning capability. Additionally, a very high p -chloroaniline selectivity (∼98%) could be obtained under mild conditions (1.0 MPa, 100°C) when H 2 is used as reductant. Characterization results and theory calculations demonstrate that introducing an appropriate amount of N/Cl species may finely modulate the local coordination environments of Zn single-atoms. The resultant axially Cl-coordinated ZnN 2 sites (Zn-N 2 Cl) possess moderated adsorption/desorption capability and lower activation barriers, in line with the Sabatier principle, thereby significantly boosting the catalytic hydrogenation performance. This work provides a simple and effective approach for developing efficient hydrogenation catalysts through manipulating the coordination structure of metal single-atom sites.