Accessing monomers from lignin through carbon-carbon bond cleavage

Area of Science:

• Biomass valorization
• Catalysis
• Macromolecular chemistry

Background:

• Lignin is an abundant aromatic macromolecule in plant cell walls, a potential feedstock for biochemicals and biofuels.
• Current lignin valorization primarily targets C-O bond cleavage, but low monomer yields persist due to recalcitrant C-C bonds.
• Selective cleavage of lignin's C-C bonds remains a significant catalytic challenge.

Purpose of the Study:

• To review and highlight strategies for cleaving lignin C-C bonds.
• To examine various catalytic approaches for lignin C-C bond depolymerization.
• To identify promising research avenues and establish guidelines for measuring C-C bond cleavage.

Main Methods:

• Examination of lignin C-C cleavage reactions, including biosynthetic (β-1, β-5, β-β, 5-5) and industrial (5-CH2-5, α-5) linkages.
• Review of catalytic approaches: homogeneous, heterogeneous, photocatalysis, and biocatalysis.
• Analysis of strategies to overcome C-C bond recalcitrance in lignin.

Main Results:

• Lignin C-C bond cleavage presents a major hurdle in efficient lignin depolymerization.
• Diverse catalytic methods show potential for cleaving various lignin C-C linkages.
• Progress in C-C bond cleavage is essential for enhancing monomer yields in lignin valorization.

Conclusions:

• Selective lignin C-C bond cleavage is critical for unlocking its full potential as a feedstock.
• Further research into catalytic C-C bond cleavage strategies is warranted.
• Standardized measurement protocols are needed to advance the field of lignin C-C bond cleavage.