Green Hydrophobic Modification of Biomass-Derived Porous Carbon: Linking Surface Chemistry, Pore Structure, and Sustainability

The hydrophobic modification of biomass-based porous carbon involves two theoretical paradigms—“exogenous coating” and “surface-confined covalent transformation”—but the underlying logical transition between them has not yet been systematically examined. This study employs a theoretical dialectical approach. Through the deconstruction of the concept of “green hydrophobic modification,” the deduction of progressive propositions, and a critical dialogue with existing research, we have constructed a three-dimensional integrated analytical framework comprising “chemical logic—spatial effects—green attributes.” The study found that the efficacy of hydrophobic modification is constrained by the synergistic contradiction between the degree of surface chemical transformation and the preservation of pore structure; exogenous modifications, such as silanization and fluorination, tend to fall into a “hydrophobicity–pore” trade-off whose severity depends on the modifier molecular size, degree of functionalization, grafting density, pore size distribution, and alkyl chain length, due to the coverage by a heterogeneous hydrophobic layer, whereas surface-confined covalent esterification based on esterification with natural organic acids directly converts oxygen-containing functional groups on the carbon surface into ester groups, achieving logical consistency between hydrophobic functionality and pore structure preservation. The study further reveals that the surface-confined covalent esterification paradigm holds a significant advantage in terms of alignment with green chemistry principles, though its applicability is limited by the abundance of surface functional groups on the carbon precursor. These findings provide clear criteria for evaluating paradigms in the green hydrophobic modification of biomass-derived porous carbon, propelling related research from methodological description toward theoretical construction. A three-way classification of modification routes is introduced (exogenous coating; exogenous reagent + surface-confined covalent transformation; truly endogenous transformation), and the verification requirements (solid-state NMR/XPS), pore-sensitive wettability metrics, and hydrolytic-stability limits of surface-confined covalent esterification are explicitly delimited.