Heteropore Conjugated Organic Reticular Subnano-Crystal for Photocatalytic Water Splitting

Abstract

2D COF-based photocatalysts exist as insoluble and difficult-to-process blocks, the layered stacking buries active sites, hindering water molecule access, while crystal defects restrict charge carrier migration/penetration. The well-defined sub-nanostructures with distinct configurations (C₂, C₃) can construct multiple pathways and intramolecular electric fields, which promote electron separation and transfer. Hence, we develop a kind of heteropore-conjugated reticular oligomers (CROs) subnano-crystals with well-defined structures, which can be regarded as a defect-free COFs segment. These sub-nanometer dots ensure sufficient exposure of active sites, enhance processability, form a “homogeneous catalyst” and consequently increase the accessibility of water molecules. Accordingly, the photocatalytic performance of series CROs is up to 129.33 μmol h^–1, improving 3–5 times over bulk COFs. Theoretical calculation shows that: Electron transfer number (ET) increased from 0.43 to 0.99 e, charge transfer distance (D) increases from 2.467 to 10.319 Å, while electron–hole overlap integral (S_r) decreases from 0.495 to 0.023, and exciton binding energy (E_b) decreases from 6.28 to 4.28 eV. The statistical product and service solutions (SPSS) method indicates that extending electron–hole separation distances and reducing exciton binding energy play a pivotal role in achieving effective electron delocalization and efficient charge transfer, thus significantly promoting the photocatalytic process.