Boosting photocatalytic nitrogen fixation performance by adjusting the intramolecular D-A structure and band gap of thiophene-based COFs

• Published in: Separation and purification technology 2025-04, Vol.356, p.129972, Article 129972
• Main Authors: Ma, Yunchao, Yao, Yuxin, Qi, Shengnan, You, Chuanxue, Wu, Yuanyuan, Liu, Chunbo, Hu, Bo, Cui, Keyu
• Format: Article
• Language: English
• Subjects: Band gap; Charge separation; Covalent organic frameworks (COFs); Donor–acceptor (D-A) structure; Electronic rich thiophene group; Photocatalytic nitrogen reduction reaction (PNRR); Triazine group
• ISSN: 1383-5866
• DOI: 10.1016/j.seppur.2024.129972

Two donor-acceptor COFs (JLNU-310 and JLNU-311) for photocatalytic nitrogen fixation were prepared. This work provides a new way to design photocatalytic nitrogen fixing materials based on COFs. [Display omitted] •Two donor-acceptor (D-A) COFs (JLNU-310 and JLNU-311) were prepared for photocatalytic nitrogen fixation.•The photocatalytic ammonia production rate of JLNU-311 with narrow band gap was increased to 325.6 umol/g/h.•The suitable band gap allows JLNU-COFs to maintain the thermodynamic activity of nitrogen reduction. Herein, we successfully synthesized two photoactive donor–acceptor (D-A) covalent organic frameworks by incorporating electric-deficient triazine and electric-rich benzotrithiophene moieties into the framework. The introduction of sulfur atom and triazine unit significantly change the intrinsic band gap of JLNU-COFs, this leads to an expanded range of light absorption, encompassing wavelengths from ultraviolet to visible. The narrow band gap of JLNU-311 allows for efficient utilization of visible light while maintaining the thermodynamic activity required for nitrogen reduction within appropriate energy bands. JLNU-311 modified with strong electron absorbing groups has higher activity to NH3 production without co-catalyst or sacrificial agent, and yield can reach 325.6 µmol/g/h. Theoretical calculation further confirm that acceptor structure can effectively regulate the band gap width, promote the adsorption, dissociation and protonation of N2 molecules on JLNU-COFs, and thus reduce the energy barrier of photocatalytic nitrogen reduction reaction (PNRR). Therefore, this study provides an effective strategy for design of active nitrogen fixing photocatalysts.