新型噻吩基共价三嗪骨架材料的制备及其高效光解水产氢性能

Novel covalent triazine frameworks incorporating thiophene moiety for enhanced photocatalytic hydrogen production

  • 摘要: 氢能作为一种清洁能源有着广阔的开发前景,利用太阳能进行高效光解水制氢是一种非常有前景的策略。共价三嗪骨架材料(CTFs)在光催化领域中的应用受到了广泛的关注。然而,传统高温离子热合成CTFs所需反应条件苛刻,使得材料失去光响应性,并且设计合成具有高光催化性能的CTFs材料仍极具挑战。对此本工作采用脒基缩聚法在温和条件下合成新型CTFs,通过单体的可控设计从分子水平引入噻吩基团构建D-A结实现光催化产氢性能的提升。本研究构筑了三种CTFs(CTF-PP、CTF-PTP以及CTF-TPT),电子供体能力更强的D-A型CTF-TPT光催化产氢活性高达15650 μmol/(g·h),而不含电子供体基团的CTF-PP光催化产氢活性只有6172 μmol/(g·h)。此外,通过电化学分析与模拟计算得出噻吩基团和三嗪基团可分别作为有效的电子供体单元和受体单元,通过引入D-A结可以在分子水平上进一步调控CTFs带隙位置并促进电荷分离和传输,进而提高光催化性能。

     

    Abstract: The increasing global demand for renewable and sustainable energy has made the development of clean and renewable energy sources crucial in addressing both global energy security and environmental challenges. Among all fuel options, hydrogen stands out due to its high energy density and emission of only water when burned, making it a highly regarded clean and promising alternative energy source. Moreover, the utilization of solar energy to produce hydrogen by efficient photolysis of water is a very promising strategy. Covalent triazine frameworks (CTFs) materials are a novel class of porous organic polymer materials that have garnered significant attention from researchers due to their exceptional characteristics, including high specific surface area, porosity, stability, and tunable active sites. In the realm of photocatalysis, CTFs exhibit remarkable light responsiveness owing to their planar π-conjugated structure and π-π stacking arrangement, which facilitate efficient charge carrier separation and migration within the material. The application of CTFs in the field of photocatalysis has received extensive attention. However, the reaction conditions for traditional high temperature ionic thermal synthesis of CTFs are harsh, which makes the material lose its photoresponsiveness. Consequently, the design and synthesis of CTF materials with exceptional photocatalytic properties remain highly challenging. The ideal photocatalyst should possess high light absorption capability and efficient carrier separation and transport efficiency. In order to enhance these properties, apart from altering the catalyst material, the incorporation of an electron donor-acceptor (D-A) junction is also a highly effective strategy. The D-A junction can precisely regulate the electron affinity between the D and A units at a molecular level to achieve charge separation and transfer. Moreover, the structural characteristics of the catalyst can significantly increase the number of active interfaces, thereby further enhancing its charge participation capability in the reaction. In CTFs materials, D-A structures also show extensive potential due to the excellent tunability of the CTFs skeleton structure. By adjusting the structure and proportion of D and A units, it becomes possible to modify the distribution position of LUMO and HOMO levels within the material, thereby accurately controlling the band structure and photoelectric properties at a molecular level. This precise control facilitates enhanced charge separation, transport, and ultimately leads to more efficient photocatalytic reactions. A novel CTFs was synthesized via amidine polycondensation under mild conditions, and D-A junctions were constructed at the molecular level through the controlled design of monomers to improve the photocatalytic hydrogen production. Herein, we successfully constructed three types of CTFs (CTF-PP, CTF-PTP and CTF-TPT). The photocatalytic hydrogen production activity of D-A type CTF-TPT with stronger electron donor capacity was as high as 15650 μmol/(g·h). The photocatalytic hydrogen production activity of CTF-PP without electron donor group was only 6172 μmol/(g·h). In addition, by means of electrochemical analysis and calculation, it has been determined that the thiophene moiety can serve as an effective electron donor unit, while the triazine moiety can function as an effective acceptor unit. Moreover, the incorporation of a donor-acceptor junction enables precise regulation of the bandgap position in CTFs at the molecular level, thereby facilitating charge separation and transport processes and ultimately enhancing photocatalytic performance.

     

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