Short-lived shallow trapping states in photocatalysts created from polymeric semiconductors impedes the effective use of charge carriers, leading to a decrease in the solar-to-hydrogen conversion efficiency of covalent triazine frameworks (CTF). In this study, methylene-modified covalent triazine frameworks (M−CTF) with increased structural distortion were synthesized through a dynamic trimerization reaction of cyano groups using the precursors of 1,4-terephthalonitrile and 1,4-phenylenediacetonitrile. The optimal M−CTF catalyst obtained in this approach showed persistent shallow trapping states through n-π* electronic transitions, leading to a noticeable red-shift in the light absorption edge to 600 nm. Femtosecond transient absorption spectroscopy verified the existence of shallow trapping states with extended lifetimes (1103.8 ps) in M−CTF. The distorted structure promote increased involvement of photo-induced electrons in reducing water to generate H2, leading to a substantial improvement in the ability of M−CTF to catalyze the production of H2. M−CTF sample loaded with Pt cocatalysts exhibited an impressive efficiency of 10.1 mmol·g−1·h −1 in producing H2 via photocatalysis under visible light (λ > 420 nm), marking a tenfold improvement compared to the original CTF. The findings underscore the significance of structural distortion in CTF for achieving long-lasting shallow trapping states, leading to improved photocatalytic efficiency.

中文翻译：

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通过在扭曲的共价三嗪框架中实现持久的浅捕获态来增强光催化氢的产生


由聚合物半导体产生的光催化剂中短寿命的浅捕获态阻碍了载流子的有效利用，导致共价三嗪框架 （CTF） 的太阳能到氢的转换效率降低。在这项研究中，通过使用 1,4-对苯二腈和 1,4-苯二乙腈的前体的氰基动态三聚化反应，合成了结构变形增加的亚甲基改性共价三嗪框架 （M-CTF）。通过这种方法获得的最佳 M-CTF 催化剂通过 n-π* 电子跃迁显示出持续的浅捕获态，导致光吸收边缘的明显红移至 600 nm。飞秒瞬态吸收光谱证实了 M-CTF 中存在具有延长寿命 （1103.8 ps） 的浅俘获态。扭曲的结构促进了光诱导电子在还原水生成 H2 中的参与增加，导致 M-CTF 催化 H2 产生的能力显着提高。在可见光 （λ > 420 nm） 下，负载 Pt 助催化剂的 M-CTF 样品在光催化下表现出令人印象深刻的 10.1 mmol·g-1·h -1 生产 H2 的效率，与原始 CTF 相比提高了 10 倍。这些发现强调了 CTF 中结构变形对于实现持久的浅捕获状态的重要性，从而提高光催化效率。