A recoverable polyoxometalate-ionic liquid catalyst for selective cleavage of lignin β-O-4 models under mild conditions

Abstract

The efficient and selective cleavage of the β-O-4 linkage under mild conditions represents a promising strategy to convert lignocellulose to value-added aromatic chemicals. In this work, a recoverable polyoxometalate-ionic liquid (POM-IL) catalyst has been successfully constructed by reacting H₅PMo₁₀V₂O₄₀ (HPMoV) polyoxoacids with 1-methyl-3-(4-sulfobutyl)-1H-imidazolium (BMIM-SO₃) zwitterions. Such a POM-IL catalyst can selectively and effectively convert various β-O-4 lignin models into aromatic acids and phenols under mild homogeneous conditions. Addition of ethyl acetate to the homogeneous post-reaction solution allows the easy recovery of the POM-IL catalyst for successive five recycling tests with high robustness. The dominant catalytic pathway was elucidated by a series of mechanistic studies.