Cross-Shaped Donor-π-Acceptor Covalent Organic Frameworks with Tunable Push-Pull Architectures for Effective...

Efficient photocatalysts for H₂O₂ production are pivotal for solar-to-chemical energy conversion. However, their performance remains limited by inefficient charge separation and rapid electron-hole recombination. Rational molecular design is therefore essential to enhance intrinsic charge-separation driving forces and establish efficient transport pathways. Herein, a TCNQ-based covalent organic framework (TCNQ-COF) featuring a rare cross-shaped donor-π-acceptor fragment was constructed by integrating electron-deficient TCNQ and electron-rich triphenylene into a conjugated backbone, achieving multidirectional charge-transfer pathways. Post-synthetic transformation of the cyano groups into electron-withdrawing heterocycles (pyrazole or pyrimidine, A'), when combined with triphenylene (D) and amino groups (D₁), yielded two novel COFs (Pz-COF, Pym-COF) with multilevel cross-shaped D-π-A'-D₁ architectures. This sophisticated push-pull system enables gradient-tuning of donor-acceptor interactions, thereby promoting efficient charge separation and carrier mobility. Among them, Pz-COF exhibits the highest H₂O₂ production rate (7613 µmol g^-1 h^-1). Spectroscopic and theoretical analyses further reveal a synergistic effect between acceptor strength and donor diversity in regulating intramolecular charge behavior. The proposed cross-shaped D-π-A and its multilevel D-π-A'-D₁ architectures overcome the limitations of conventional linear motifs, offering a blueprint for the development of advanced photocatalytic COFs.