Synergy of heterogeneous Co/Ni dual atoms enabling selective C-O bond scission of lignin coupling with in-situ N-functionalization

Selective cleavage of Csp2-OCH3 bond in lignin without breaking other types of C-O bonds followed by N-functionalization is fascinating for on-purpose valorization of biomass. Here, a Co/Ni-based dual-atom catalyst CoNiDA@NC prepared by in-situ evaporation and acid-etching of metal species from tailor-made metal-organic frameworks was efficient for reductive upgrading of various lignin-derived phenols to cyclohexanols (88.5%-99.9% yields), which had ca. 4 times higher reaction rate than the single-atom catalyst and was superior to state-of-the-art heterogeneous catalysts. The synergistic catalysis of Co/Ni dual atoms facilitated both hydrogen dissociation and hydrogenolysis steps, and could optimize adsorption configuration of lignin-derived methoxylated phenols to further favor the Csp2-OCH3 cleavage, as elaborated by theoretical calculations. Notably, the CoNiDA@NC catalyst was highly recyclable, and exhibited excellent demethoxylation performance (77.1% yield) in real lignin monomer mixtures. Via in-situ cascade conversion processes assisted by dual-atom catalysis, various high-value N-containing chemicals, including caprolactams and cyclohexylamines, could be produced from lignin. (c) 2024 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.