One-pot self-assembly synthesis of H3+xPMo12−xVxO40@[Cu6O(TZI)3(H2O)9(NO3)n]·(H2O)15 for enhanced proton conduction materials

• Published in: New journal of chemistry Vol. 46; no. 8; pp. 3909 - 3915
• Main Authors: Xin, Yuxiang, Zhou, Yijia, Dong, Longzhang, Wei, Pengpeng, Zou, Xiaoyan, Zhang, Fengming, Li, Guangming
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 01.01.2022
• Subjects: Crystal structure; Fuel cells; Leaching; Metal-organic frameworks; Polyoxometallates; Proton conduction; Self-assembly; Water chemistry
• ISSN: 1144-0546; 1369-9261
• DOI: 10.1039/d1nj06090b

Due to their strict operating conditions, complicated manufacturing process and unacceptable costs, commercial Nafion-based membranes for fuel batteries are blocked for large-scale applications. Thus, the development of new types of proton conduction materials for fuel cells is impending. Herein, we develop a simple self-assembly solvothermal method to synthesize a series of complexes PMoVx@rht-MOF-1 (PMoVx = molybdovanadophosphoric acids, rht-MOF-1 = [Cu6O(TZI)3(H2O)9(NO3)]n·15H2O) in which a series of PMoVx are encapsulated in the porous rht-MOF-1 framework. The crystal structures of PMoVx@rht-MOF-1 have been confirmed by X-ray diffraction analysis. Complexes 1–4 (1, x = 1; 2, x = 3; 3, x = 5; 4, x = 8) are further characterized by FT-IR, TGA, PXRD, SEM analyses and N2 adsorption–desorption isotherms. The systematic Nyquist experiments reveal that the proton conductivity of complexes 1–4 is dominated by the number of protons in the polyoxometalates (POMs). Strikingly, complex 4 exhibits an outstanding proton conductivity of 8.03 × 10−3 S cm−1 at 343 K under 98% RH among the POMs@MOFs composites. Further, the co-relationship between the structures in terms of PMoVx, water molecules in pore channels and proton conductivity of complexes 1–4 has been investigated. The mechanism of proton conductivity is proposed. This approach provides an easy route to prepare POMs@MOFs, which can effectively prompt the proton conductivity of POMs and prevent the leaching of the POMs in POMs@MOFs.