Issue 11, 2024

Oxidative cleavage of β-O-4 bonds in lignin model compounds with polymer-supported Ni–Salen catalysts

Abstract

Transition metal-catalyzed lignin oxidative cleavage reactions have attracted considerable attention. In this work, polymerized ionic liquid-tagged Salen ligands have been initially synthesized, followed by anion exchange, and then coordination with Ni(II) via a –N2O2– tetradentate structure. Finally, the as-obtained Ni–Salen complexes were polymerized to give a Ni–Salen polymer catalyst (poly-Ni-[Salen-Vim][OAc]2). The resulting catalyst showed 99% conversion and 88% selectivity to oxidative cleavage products for the oxidative cleavage of a lignin model compound (2-phenoxy-1-phenylethanone) without any base additive at 110 °C. The polymeric ionic liquid-tagged Salen(Ni) catalysts can be separated easily by centrifugation after the reaction and recycled for five runs with a slight loss of activity. Additionally, studies on birch lignin depolymerization indicated that polymer-supported Ni Salen catalysts were able to cleave β-O-4 linkages to produce dimeric products. Further investigation suggests that the oxidative cleavage reaction was proceeded via a radical pathway.

Graphical abstract: Oxidative cleavage of β-O-4 bonds in lignin model compounds with polymer-supported Ni–Salen catalysts

Supplementary files

Article information

Article type
Paper
Submitted
27 Jun 2024
Accepted
18 Sep 2024
First published
19 Sep 2024
This article is Open Access
Creative Commons BY-NC license

RSC Sustain., 2024,2, 3397-3408

Oxidative cleavage of β-O-4 bonds in lignin model compounds with polymer-supported Ni–Salen catalysts

Q. Liu, D. Yang, X. Zhao, Z. Xu, J. Ding, D. Wu, N. An, H. Liao and Z. Hou, RSC Sustain., 2024, 2, 3397 DOI: 10.1039/D4SU00331D

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