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<p>Developing efficient seawater-compatible photocatalysts for solar H<sub>2</sub> production with high activity and durability is critical. Covalent organic frameworks (COFs) are ideal photocatalysts for H<sub>2</sub> production owing to their periodic architectures, chemical robustness, and facile functionalization. However, current synthesis methods of COFs typically involve complex vacuum operations and long reaction times at high temperatures, limiting their scalability for practical production. Herein, we introduce a continuous-flow route that furnishes COFs on minute timescales (∼5 min) with controllable crystallinity and optoelectronic properties, batch-to-batch reproducibility, and straightforward scale-out. Using this platform, three β-ketoenamine COFs are obtained by Schiff-base condensation of 1,3,5-triformylphloroglucinol (Tp) with biphenyldiamines (BD) bearing–H,–CH<sub>3</sub>, or–F substituents. Under visible light (<i>λ</i> &gt; 420 nm), the methylated TpBD-CH<sub>3</sub> shows the highest hydrogen-evolution rate—107.2 mmol g<sup>−1</sup> h<sup>−1</sup> in simulated seawater (3.5 wt% NaCl) and 73.1 mmol g<sup>−1</sup> h<sup>−1</sup> in real seawater—surpassing most reported COF systems under comparable conditions. Spectroscopic, electrochemical measurements, and DFT/TDDFT indicate that methyl substitution narrows the band gap, strengthens visible absorption, reduces interfacial charge-transfer resistance, increases excited-state hole-electron separation, and affords an H* adsorption free energy close to thermoneutral—features that together account for the superior photocatalytic hydrogen production activity. This work establishes continuous flow as an efficient, scalable platform for high-quality COFs and provides clear design guidelines for seawater-compatible photocatalysts toward sustainable hydrogen production.</p>

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Rapid continuous-flow synthesis of functional β-ketoenamine COFs for robust photocatalytic H2 evolution in real seawater

  • 期刊论文

  • 发表日期：

    2026年3月2日

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  • Liyun Huang,
  • Aoran Cui,
  • Zhensui Liu,
  • Xue Jiang,
  • Defei Liu,
  • Ying Wang,
  • Wenbing Yuan

摘要

Developing efficient seawater-compatible photocatalysts for solar H2 production with high activity and durability is critical. Covalent organic frameworks (COFs) are ideal photocatalysts for H2 production owing to their periodic architectures, chemical robustness, and facile functionalization. However, current synthesis methods of COFs typically involve complex vacuum operations and long reaction times at high temperatures, limiting their scalability for practical production. Herein, we introduce a continuous-flow route that furnishes COFs on minute timescales (∼5 min) with controllable crystallinity and optoelectronic properties, batch-to-batch reproducibility, and straightforward scale-out. Using this platform, three β-ketoenamine COFs are obtained by Schiff-base condensation of 1,3,5-triformylphloroglucinol (Tp) with biphenyldiamines (BD) bearing–H,–CH3, or–F substituents. Under visible light (λ > 420 nm), the methylated TpBD-CH3 shows the highest hydrogen-evolution rate—107.2 mmol g−1 h−1 in simulated seawater (3.5 wt% NaCl) and 73.1 mmol g−1 h−1 in real seawater—surpassing most reported COF systems under comparable conditions. Spectroscopic, electrochemical measurements, and DFT/TDDFT indicate that methyl substitution narrows the band gap, strengthens visible absorption, reduces interfacial charge-transfer resistance, increases excited-state hole-electron separation, and affords an H* adsorption free energy close to thermoneutral—features that together account for the superior photocatalytic hydrogen production activity. This work establishes continuous flow as an efficient, scalable platform for high-quality COFs and provides clear design guidelines for seawater-compatible photocatalysts toward sustainable hydrogen production.