Proton conductance and mechanism of the synthesized two Co(II)-CPs/Nafion composite membranes based on N-heterocyclic carboxylic acid-based ligand

• Published in: Journal of solid state chemistry 2024-01, Vol.329, p.124421, Article 124421
• Main Authors: Qin, Tianrui, Li, Duqingcuo, Shi, Zhan, Xiong, Dingqi, Dong, Xiuyan, An, Ning, Chu, Yinghao
• Format: Article
• Language: English
• Subjects: Coordination polymers; N-heterocyclic carboxylic acid-based ligand; Proton conduction; Structural regulation and control
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/j.jssc.2023.124421

In this study, we synthesized two CPs, [Co(L)·H2O]n (1) and {[Co(L)·H2O](dpa)0.5}n (2) [H2L = 4,4'-(2,6-pyrazinediyl)dibenzoic acid, dpa = (E)-4-(2-(pyridin-4-yl)vinyl)pyridine] by a hydrothermal method. The materials were characterized by single-crystal X-ray diffraction (XRD), powder X-ray diffraction (PXRD), infrared (IR) spectroscopy, and elemental analysis. The conductivities and activation energies of 1–2/Nafion and pure Nafion were tested and calculated by electrochemical testing methods such as CV and EIS, respectively. The results show that compared with pure Nafion, the doping of CPs with Nafion leads to a certain degree of increase in the proton conductivity of the composite membranes, and in addition, the conductivity of 2 is better than that of 1. We have also analyzed the proton transport paths in the internal structure of 1–2 by simulation through theoretical calculations, which provides a platform for the study of the proton conductivity mechanism of the materials, and then provides ideas for designing different high-performance PEM materials. Compared with pure Nafion, the conductivity of 1–2/Nafion composite membranes were all improved to some extent. In addition, the relative conductivity of 2 was found to be better than that of 1 after comparison. The protons of 1 may be transported via the paths C6→O5, C9→O3, C10→O4, O5→O2, and O5→O3, while 2 is C7→O4, C9→O5, and C10→O2. [Display omitted] •Two Co(Ⅱ)-based metal complexes [Co(L)·H2O]n (1) and {[Co(L)·H2O](dpa)0.5}n (2) were synthesized.•CPs 1–2 are 2D network structures that are rich in hydrogen bonds.•Proton conduction properties of 1–2 were studied.•The proton transport paths for 1–2 are derived computationally.