Multidimensional Band-Structure Engineering in Chalcogen-Substituted Covalent Organic Frameworks Through Electrophilicity, Lattice Strain, and Defect Regulation

Band-structure engineering underpins many modern information and energy technologies; however, achieving precise multidimensional band-structure tuning within a single, structurally well-defined material platform remains a significant challenge. Herein, a covalent organic frameworks (COFs)-based strategy is presented that translates this limitation into a controllable problem of atomic composition. Two isoreticular COF series of 2D TAPE-COFs and 1D TAPP-COFs were synthesized by co-condensing tetratopic aromatic amine nodes with binary mixtures of thiophene-2,5-dicarboxaldehyde (TDA) and furan-2,5-dicarboxaldehyde (FDA). Furthermore, these COFs exhibit continuously tunable band-structure properties, including work function, ionization potential, bandgap, and Fermi-level, as a direct result of the precise modulation of the chalcogen-based linkers composition. Combined experimental and density functional theory analyses reveal that these cooperative shifts arise from the heteroatom contrast between S and O, which governs the framework electronegativity, internal strain, and defect energetics. The TAPE-COFs were applied to the photocatalytic oxidation of 5-hydroxymethylfurfural (HMF), achieving a volcano-shaped conversion profile originating from the synergistic interplay between the ordered band structure and the internal donor (D)–acceptor (A) architecture.