Free radical reaction promoted by ionic liquid: a route for metal-free oxidation depolymerization of lignin model compound and lignin.

Ionic liquid 1-benzyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BnMIm][NTf2]) can promote the generation of the ˙OOH free radical and thereby efficiently transformed the β-O-4 lignin model compound 2-phenoxyacetophenone into benzoic acid and phenol using O2 as the oxidant. Furthermore, the IL-based metal-free catalytic system can also depolymerize other lignin model compounds and organosolv lignin effectively.