Lignin and metal–organic frameworks: mutual partners on the road to sustainability

Considering the two limitations of the biocompatibility of metal–organic-frameworks (MOFs) and the low utilization of lignin biomass, herein, we review the interaction between lignin macromolecules and MOFs to promote their high-end applications and sustainability. Firstly, lignin and lignin derivatives can coordinate with metal ions to form bio-based MOFs due to their biocompatibility and surface-rich functional groups, which solves the difficulty of applying the original MOFs in biomedicine and other fields. We introduce the structure, coordination process, and advantages of applying bio-based MOFs in detail and discuss the problem that powdered MOFs are easily blocked and difficult to be separated and recovered. Secondly, MOFs can be used as catalysts to facilitate the conversion of lignin to liquid fuels and fine chemicals, thereby alleviating the energy shortage. We discuss the mechanism and products from the redox depolymerization of lignin using MOFs and their derivatives. The opportunities and challenges encountered in bio-based MOFs and selective cleavage of lignin are discussed based on several perspectives. It is hoped that this study can provide good theoretical guidance for the synthesis of bio-based MOFs and the conversion of lignin.