Journal of Energy Chemistry ›› 2023, Vol. 79 ›› Issue (4): 535-549.DOI: 10.1016/j.jechem.2022.12.020

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Cooperative catalysis of Co single atoms and nanoparticles enables selective CAr—OCH3 cleavage for sustainable production of lignin-based cyclohexanols

Baoyu Wanga,c, Peng Zhoub, Ximing Yanc, Hu Lia,*, Hongguo Wua,d,*, Zehui Zhangb,*   

  1. aNational Key Laboratory of Green Pesticide, Key Laboratory of Green Pesticide & Agricultural Bioengineering, Ministry of Education, State-Local Joint Laboratory for Comprehensive Utilization of Biomass, Center for R&D of Fine Chemicals, Guizhou University, Guiyang 550025, Guizhou, China;
    bKey Laboratory of Catalysis and Material Sciences of the State Ethnic Affairs Commission & Ministry of Education, College of Chemistry and Material Sciences, South-Central University for Nationalities, Wuhan 430074, Hubei, China;
    cGuangxi Key Laboratory of Green Chemical Materials and Safety Technology, Beibu Gulf University, Qinzhou 535011, Guangxi, China;
    dCollege of Pharmacy, Guizhou University, Guiyang 550025, Guizhou, China
  • Received:2022-09-25 Revised:2022-12-09 Accepted:2022-12-11 Online:2023-04-15 Published:2023-05-30
  • Contact: * E-mail addresses: hli13@gzu.edu.cn (H. Li), whg0408@126.com (H. Wu), zehuizh@mail.ustc.edu.cn (Z. Zhang).

Abstract: In this work, a dual-size MOF-derived Co catalyst (0.2Co1-NPs@NC) composed of single atoms (Co1) and highly dispersed nanoparticles (Co NPs) was prepared by in-situ Zn evaporation for the high-performance conversion of lignin-derived o-methoxyphenols (lignin oil) to cyclohexanols (up to 97% yield) via cascade demethoxylation and dearomatization. Theoretical calculations elaborated that the dual-size Co catalyst exhibited a cooperative effect in the selective demethoxylation process, in which the Co NPs could initially dissociate hydrogen at lower energies while Co1 remarkably facilitated the cleavage of the CAr — OCH3 bond. Moreover, the intramolecular hydrogen bonds formed in the o-methoxy-containing phenols were found to result in a decrease in the bond energy of the CAr — OCH3 bond, which was more prone to be activated by the dual-size Co sites. Notably, the pre-hydrogenated intermediate (e.g., 2-methoxycyclohexanol from guaiacol) is difficult to undergo demethoxylation, indi-cating that the selective CAr — OCH3 bond cleavage is a prerequisite for the synthesis of cyclohexanols. The 0.2Co1-NPs@NC catalyst was highly recyclable with a neglect decline in activity during five consecu-tive cycles. This cooperative catalytic strategy based on the metal size effect opens new avenues for bio-mass upgrading via enhanced C — O bond cleavage of high selectivity.

Key words: Biomass conversion, Heterogeneous catalysis, C—O bond cleavage, Lignin valorization, Cyclohexanols