Unraveling the physical genome of biochar

Biochar, a porous carbonaceous material produced through the thermochemical conversion of biomass, is garnering significant attention for its critical roles in carbon sequestration, sustainable energy solutions, and advanced materials engineering. The strategic and precise manipulation of its intrinsic physical properties—such as hierarchical porosity, mechanical robustness, thermal conductivity, electrical transport behavior, and tunable optical response—has now emerged as a fundamental enabler for designing next-generation multifunctional carbon systems. This review provides a comprehensive, integrated, and multiscale examination of these physical characteristics, with a particular focus on elucidating the complex, often synergistic relationships among them. By establishing robust correlations spanning from the atomic-level molecular structure and chemical functionality to the microstructural morphology and ultimately the macroscopic performance, a coherent structure-property-function framework is constructed. This framework is essential for guiding the rational design of biochar-based materials. Furthermore, persistent knowledge gaps and the challenges posed by these gaps are critically highlighted. Finally, future pathways toward precision-engineered biochar for high-value applications in energy storage, photothermal conversion, environmental remediation, and beyond are proposed.