Unprecedentedly high activity and selectivity for hydrogenation of nitroarenes with single atomic Co1-N3P1 sites

Abstract

Transition metal single atom catalysts (SACs) with M1-Nx coordination configuration have shown outstanding activity and selectivity for hydrogenation of nitroarenes. Modulating the atomic coordination structure has emerged as a promising strategy to further improve the catalytic performance. Herein, we report an atomic Co1/NPC catalyst with unsymmetrical single Co1-N3P1 sites that displays unprecedentedly high activity and chemoselectivity for hydrogenation of functionalized nitroarenes. Compared to the most popular Co1-N4 coordination, the electron density of Co atom in Co1-N3P1 is increased, which is more favorable for H2 dissociation as verified by kinetic isotope effect and density functional theory calculation results. In nitrobenzene hydrogenation reaction, the as-synthesized Co1-N3P1 SAC exhibits a turnover frequency of 6560 h−1, which is 60-fold higher than that of Co1-N4 SAC and one order of magnitude higher than the state-of-the-art M1-Nx-C SACs in literatures. Furthermore, Co1-N3P1 SAC shows superior selectivity (>99%) toward many substituted nitroarenes with co-existence of other sensitive reducible groups. This work is an excellent example of relationship between catalytic performance and the coordination environment of SACs, and offers a potential practical catalyst for aromatic amine synthesis by hydrogenation of nitroarenes.

Cobalt Single Atoms Anchored on Oxygen‐Doped Tubular Carbon Nitride for Efficient Peroxymonosulfate Activation: Simultaneous Coordination Structure and Morphology Modulation

“…Compared to the Co−N 4 moiety, the changed current density of Co−N 3 O 1 −1 was much higher, suggesting that Co−N 3 O 1 −1 manifested a better conductivity for electron migration and possessed a faster reaction rate [6] . Furthermore, the charge state of the cobalt atom in Co−SO 4 * (active sites) became more positive by 0.05 e − in comparison with Co−SO 5 *, hinting that SO 4 * and OH* could slightly increase the charge state of the cobalt atom [14b] …”

“…Engineering the coordination environment of single atoms has been proved as an efficient strategy to selectively generate active radicals [14b] . To identify the dominated active species generated in these systems, radical quenching experiments were employed.…”

Research progress of asymmetrically coordinated single-atom catalysts for electrocatalytic reactions

“…Moreover, there are also contributions from asymmetric coordination environments in the fields of the HER, 88 the NRR, 100 and nitrobenzene. 101…”

Neighboring Cationic Vacancy Assisted Adsorption Optimization on Single-Atom Sites for Improved Oxygen Evolution

“…Single-atom catalysts (SACs) with the utmost atomic utilization exhibit excellent catalytic activity in energy catalysis. Meanwhile, their uniform active sites with unique electronic microenvironments provide a perfect model for exploring the reaction mechanism. − The catalytic performance of SACs is intently correlated with the adsorption strengths of intermediates on reaction active sites. − In addition to the first-shell coordination of the metal active center, the adsorption strengths of intermediates can also be tuned via the second-shell neighboring microenvironment of single atoms. − For example, the electronic interaction between the atomic Fe center and neighboring P and S atoms weakened the binding energy for the intermediates, which enhanced the intrinsic performance of Fe sites in the oxygen reduction reaction . In another case, a neighboring S anion was introduced in Ru-N-C catalysts to increase the electron cloud density of the central Ru sites, which decreased the adsorption strength of *OH and improved the oxygen reduction performance .…”