Photoelectrochemical (PEC) water reduction, converting solar energy into environmentally friendly hydrogen fuel, requires delicate design and synthesis of semiconductors with appropriate bandgaps, suitable energy levels of the frontier orbitals, and high intrinsic charge mobility. In this work, the synthesis of a novel bithiophene‐bridged donor–acceptor‐based 2D sp²‐carbon‐linked conjugated polymer (2D CCP) is demonstrated. The Knoevenagel polymerization between the electron‐accepting building block 2,3,8,9,14,15‐hexa(4‐formylphenyl) diquinoxalino[2,3‐a:2′,3′‐c]phenazine (HATN‐6CHO) and the first electron‐donating linker 2,2′‐([2,2′‐bithiophene]‐5,5′‐diyl)diacetonitrile (ThDAN) provides the 2D CCP‐HATNThDAN (2D CCP‐Th). Compared with the corresponding biphenyl‐bridged 2D CCP‐HATN‐BDAN (2D CCP‐BD), the bithiophene‐based 2D CCP‐Th exhibits a wide light‐harvesting range (up to 674 nm), a optical energy gap (2.04 eV), and highest energy occupied molecular orbital–lowest unoccupied molecular orbital distributions for facilitated charge transfer, which make 2D CCP‐Th a promising candidate for PEC water reduction. As a result, 2D CCP‐Th presents a superb H₂‐evolution photocurrent density up to ≈7.9 µA cm⁻² at 0 V versus reversible hydrogen electrode, which is superior to the reported 2D covalent organic frameworks and most carbon nitride materials (0.09–6.0 µA cm⁻²). Density functional theory calculations identify the thiophene units and cyano substituents at the vinylene linkage as active sites for the evolution of H₂.

中文翻译：

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噻吩桥式供体受体sp2碳键连接的二维共轭聚合物，作为光电还原水的阴极

光电化学（PEC）用水的减少，将太阳能转化为环保的氢燃料，需要对半导体进行精细的设计和合成，并具有适当的带隙，适当的前沿轨道能级和高的固有电荷迁移率。在这项工作中，合成了一种新型的基于联噻吩桥的供体-受体的2D sp ²演示了碳连接共轭聚合物（2D CCP）。电子接受结构单元2,3,8,9,14,15-六（4-甲酰基苯基）二喹喔啉[2,3-a：2'，3'-c]吩嗪（HATN-6CHO）之间的Knoevenagel聚合第一个供电子接头2,2'-（[[2,2'-联噻吩] -5,5'-二基）二乙腈（ThDAN）提供2D CCP-HATNThDAN（2D CCP-Th）。与相应的联苯桥连2D CCP-HATN-BDAN（2D CCP-BD）相比，基于联噻吩的2D CCP-Th具有较宽的光收集范围（最大674 nm），光能隙（2.04 eV） ，并且具有最高的能量占据的分子轨道-最低的未占据的分子轨道分布，以促进电荷转移，这使2D CCP-Th成为减少PEC用水的有希望的候选者。结果，二维CCP-Th呈现出极好的H ₂与可逆氢电极相比，0 V时的演化光电流密度高达≈7.9µA cm ^-2，优于报道的二维共价有机骨架和大多数氮化碳材料（0.09–6.0 µA cm ^-2）。密度泛函理论计算确定亚乙烯基键处的噻吩单元和氰基取代基为H ₂析出的活性位点。