Covalent organic frameworks (COFs) have recently shown great prospects for their photocatalytic applications in solar-to-hydrogen conversion. Nevertheless, most of the COFs were synthesized as crystalline bulk powders, impeding the exposure of surface catalytically active sites. Developing a noninvasive and expedient route to exfoliate COFs in liquids still remains a great challenge. Herein, two typical 1,3,5-tri(thiophen-2-yl)benzene (TTB)-based COFs (one possesses non-donor–acceptor constitution, denoted as TTB-PB, while the other possesses donor–acceptor constitution, denoted as TTB-PT) were synthesized via Schiff-base condensation reactions. Subsequently, these bulk COFs were exfoliated via a facile electrochemical strategy in aqueous systems. The obtained exfoliated COFs can not only facilitate photo-triggered exciton dissociation but also afford more accessible active sites and enhanced hydrophilicity. Consequently, the exfoliated COFs exhibited much higher photocatalytic capabilities for H₂ evolution from water in sharp contrast to their unexfoliated precursors. It is to be noted that the exfoliated donor–acceptor COFs achieved a maximum H₂ evolution rate of 27.24 mmol h⁻¹ g⁻¹, which is superior to that of the exfoliated non-donor–acceptor COF (i.e., 9.86 mmol h⁻¹ g⁻¹), and also ranks at the top of the state-of-the-art thiophen-based COF photocatalysts in the literature. This work enriches the fabrication approach of COF exfoliation. Furthermore, utilizing the synergetic strategy of aqueous electrochemical exfoliation and suitable molecular design, TTB-based COFs demonstrate promising photocatalytic activity.

中文翻译：

---

电化学剥离的共价有机框架可改善光催化析氢

共价有机框架（COF）最近在太阳能-氢转化中的光催化应用显示出巨大的前景。然而，大多数COF都是作为结晶散装粉末合成的，阻碍了表面催化活性位点的暴露。开发一种非侵入性且便捷的方法来去除液体中的 COF 仍然是一个巨大的挑战。本文中，两种典型的1,3,5-三（噻吩-2-基）苯（TTB）基COF（一种具有非给体-受体结构，表示为TTB-PB，而另一种具有给体-受体结构，表示为TTB-PT）是通过席夫碱缩合反应合成的。随后，这些块状 COF 在水性系统中通过简单的电化学策略进行剥离。所获得的剥离COF不仅可以促进光触发激子解离，还可以提供更容易接近的活性位点和增强的亲水性。因此，剥离的COF表现出更高的从水中析出H ₂的光催化能力，与其未剥离的前体形成鲜明对比。值得注意的是，剥离的供体-受体COF实现了27.24 mmol h ^-1 g ^-1的最大H ₂释放速率，这优于剥离的非供体-受体COF（即9.86 mmol h ^{- ）。 1} g ^-1），并且在文献中也位居最先进的噻吩基COF光催化剂之首。这项工作丰富了COF剥离的制造方法。此外，利用水性电化学剥离和合适的分子设计的协同策略，基于TTB的COF表现出有前景的光催化活性。