Tailoring photocatalytic performance through D–π–A architecture: structure–property correlations in β-ketoenamine covalent organic frameworks

Covalent organic frameworks (COFs) are an emerging class of crystalline porous polymers with significant potential in photocatalysis due to their highly tunable chemical structures and optoelectronic properties. Precise design of building blocks to construct a “donor–π bridge–acceptor” (D–π–A) architecture provides an ideal platform for efficient separation and transport of photogenerated charges. In this work, density functional theory (DFT) and time‑dependent density functional theory (TD‑DFT) calculations were employed to systematically investigate the structure–property relationships governing the optoelectronic and photocatalytic performance of β‑ketoenamine COFs. Through quantitative electronic structure analysis and systematic structural comparison, we demonstrate that charge separation and transfer efficiency are critically governed by three interconnected factors: the π-conjugation length of the donor unit, the electronic character of the acceptor moiety, and the functional nature of substituents. Moderate donor extension (e.g., biphenyl), keto‑based acceptors, and balanced electron‑donating groups (e.g., methoxy) collectively promote optimal charge delocalization, spatial separation, and visible-light absorption. Furthermore, the facile keto–enol tautomerism, characterized by a moderate energy barrier and accompanied by distinct spectral shifts, underpins the dynamic structural adaptability and tunable photophysical response of these COFs. Asymmetric design strategies further enhance intramolecular charge transfer and narrow the band gap. These findings establish a rational multi‑parameter framework for the molecular engineering of high‑performance COF‑based photocatalysts, offering clear guidelines for advancing efficient solar‑driven hydrogen production.

DFT/TD-DFT Theoretical Calculations Study on the Structure-Property Relationship Between D-π-A Architecture and Photocatalytic Performance of β-Ketoenamine COFs.