Crystalline porous materials for catalytic conversion of lignin-related substances

The conversion of the biomass into eco-friendly fuels and chemicals has been exten-sively recognized as the essential pathway to achieve the sustainable economy and carbon neutral society.Lignin,as a kind of promising biomass energy,has been certified to produce the high-valued chemicals and fuels.Numerous efforts have been made to develop various catalysts for lignin catalytic conversion.Both metal-organic frameworks(MOFs)and covalent organic frameworks(COFs)belong to very important heterogeneous porous catalysts due to their regular porous struc-tures,high specific surface area,and precisely tailored diversities.In the review,thefirst part focused on the catalytic conversion of lignin,lignin model compounds,and lignin derivatives using the pristine MOFs,functional MOF composites,and MOF-derived materials.The second part summarized the catalytic conversion of lignin model compounds using pristine COFs and functional COF composites.The review here mainly concentrated on the design of the materials,screening of catalytic conditions,and explorations of the corresponded mechanisms.Specifically,(1)we summarized the MOF-and COF-based materials for the effects on the catalytic trans-formation of lignin-related substances;(2)we emphasized the catalytic mechanism of C–C and C–O bonds cleavage together with the structure–activity relationships;(3)we in-depth realized the relationship between the chemical/electronic/structural properties of the MOF-and COF-based catalysts and their catalytic performance for lignin-related substances.Finally,the challenges and future perspectives were also discussed on the catalytic conversion of lignin-related substances by MOF-and COF-based catalysts.