Wood‐MOF Thermoelectrics for Heat and Power Harvesting

Thermoelectric materials and devices enable to harvest heat energy from the environment, which offers a promising solution for addressing the critical issue of conventional fossil fuels for energy supply. However, sustainable development of low‐grade heat conversion to electricity is limited by materials and technologies. Herein, inspired by the conduction of water molecules and ions in trees, natural wood is chemically modified and synthesized to a nanostructured wood/metal‐organic framework (wood/MOF) gradient, in which it enables the driving of the ions movements through charged nanochannels for enhancing the generation of the thermally generated voltage. This has resulted in a 1200% increased differential thermal voltage of wood/MOF gradient compared to that of natural wood due to the thermophoretic mobility difference between the negative and positive ions. An electric double layer is formed among cellulose nanofibrils with a distance of approximately 4.8–7 nm enabling a favorable ionic regulation performance and a continuous output voltage of about 1.2 V, which has demonstrated its potential as a low‐grade heat and power harvesting system for heat‐to‐electricity conversion. Coupling with its long‐term durability and low environmental impact advantages, this research provides insights into an innovative “wood‐sunlight‐thermal energy” tripartite system for clean electricity generation, which enables large‐scale production from such sustainable materials.