Wang Yonghong, Liang Xiaoxiao, Wang Ming, Wang Jiahui, Gao Yanan, Lu Fei
Key Laboratory of Ministry of Education for Advanced Materials in Tropical Island Resources, School of Chemistry and Chemical Engineering, Hainan University, Haikou 570228, China.
Molecules. 2025 Feb 21;30(5):1004. doi: 10.3390/molecules30051004.
Covalent organic frameworks (COFs) hold promising potential as high-temperature proton conductors due to their highly ordered nanostructures and high specific surface areas. However, due to their limited functional groups and poor membrane-engineering properties, finding practical applications for COF-based proton-conducting materials still remains challenging. Herein, we proposed a universal strategy to fabricate proton-conducting composite membranes by the incorporation of sulfonic acid-bearing COFs and zwitterionic poly(ionic liquid)s (PILs) via in situ polymerization. Zwitterionic PILs with methanesulfonate counter ions can work as the intrinsic proton sources, and the sulfonic acid groups on the COF nanochannels can act as the extrinsic proton suppliers. Benefiting from the spatial nanoconfinement of long-range ordered nanochannels and the enhanced electrostatic interactions with PILs, the COFs with high densities of sulfonic acid groups can endow the as-prepared composite membrane (PIL@TpBD(SOH)) with a comparable anhydrous proton conductivity of 3.20 × 10 S cm at 90 °C, which is much higher than that of conventional Nafion (~10 S cm at 90 °C under anhydrous condition). H NMR DOSY spectra reveal that both the diffusion and dissociation of protons can be drastically facilitated upon nanoconfinement, demonstrating the promising efficiency of nanochannels in proton conduction. Moreover, the obtained composite membranes possess outstanding mechanical and thermal stability, which is crucial for their practical application. This study demonstrates proton conduction elevation in nanoconfined PILs and provides a promising insight into the engineering of stable COF-based proton-conducting materials.
共价有机框架材料（COFs）因其高度有序的纳米结构和高比表面积，作为高温质子导体具有广阔的应用潜力。然而，由于其官能团有限且膜工程性能较差，寻找基于COF的质子传导材料的实际应用仍然具有挑战性。在此，我们提出了一种通用策略，通过原位聚合将含磺酸的COFs和两性离子聚离子液体（PILs）结合来制备质子传导复合膜。带有甲磺酸盐抗衡离子的两性离子PILs可以作为内在质子源，COF纳米通道上的磺酸基团可以作为外在质子供应者。受益于长程有序纳米通道的空间纳米限域作用以及与PILs增强的静电相互作用，具有高密度磺酸基团的COFs可以赋予所制备的复合膜（PIL@TpBD(SOH)）在90℃时具有3.20×10 S cm的可比无水质子传导率，这远高于传统的Nafion（在无水条件下90℃时约为10 S cm）。1H NMR DOSY光谱表明，在纳米限域作用下，质子的扩散和解离都能得到显著促进，证明了纳米通道在质子传导方面具有良好的效率。此外，所获得的复合膜具有出色的机械和热稳定性，这对其实际应用至关重要。这项研究证明了纳米限域PILs中质子传导率的提高，并为稳定的基于COF的质子传导材料的工程设计提供了有前景的见解。
