Construction and functionality of heat conversion wood composite materials based on transition metal compounds

Thermal energy plays an indispensable role in social activities and can be transformed among various energy sources. Transition metal compound (TMC) enables the efficient conversion of light, electrical and magnetic energy into thermal energy due to the competition and coexistence between its strongly correlated electronic systems and inherent charge, spin, orbital and other degree of freedom and ordered phase. However, used in the form of powder and crystal, TMC owns the problems of oxidation polymerization, volume change, high heat dissipation and collection difficulties, which limits its heat conversion efficiency. Wood has natural hierarchical pore structure and could supply stable mechanical support for TMC. TMC can be uniformly loaded into wood micro-nano surfaces or porous structures by forming covalent bond, ionic bond, hydrogen bond, van der Waals forces with the chemical components of the wood to form TMC@wood composite materials. In addition, wood's excellent thermal management ability can regulate thermal energy to improve heat conversion efficiency. Based on the lign-cellulosic macromolecular network configuration of wood, we discussed the combination method and interfacial binding mechanism of TMC with raw wood, delignification wood and carbonized wood. We further discussed the thermal transformation mechanisms of non-radiative relaxation, relaxation loss and metal-insulator transition of TMC, the functional applications of TMC@wood composite materials in the fields of desalination, oil-water separation, building energy conservation and fire warning are presented. Finally, in view of providing ideas for advanced functionalization and energy conversion of wood, the current advantages and challenges of thermal conversion of TMC@wood are summarized.