Enhancement of Hydroxide Conduction by Incorporation of Metal- Organic Frameworks into a Semi-Interpenetrating Network

摘要

In order to overcome the trade-off barrier between conductivity and stability in anion exchange membranes and also to investigate the effect of the metal-organic framework (MOF) to resolve this limitation, two membranes (semi-interpenetrating network (semi-IPN) and semi-IPN MOF) were prepared through using the solution casting method. The membranes were characterized by FT-IR, H-1 NMR, BET, scanning electron microscopy, and thermogravimetric analysis. Moreover, the effect of metal-organic frameworks was accurately investigated on the membrane features such as ion exchange capacity, water uptake, swelling ratio, hydroxide ion conductivity, thermal and mechanical properties, methanol crossover, single-cell performance, and alkaline stability. The results indicated that the enhancement of ion exchange capacity (1.92 mequiv.g(-1) vs 2.40 mequiv.g(-1)) caused by increased quaternary functional groups resulted in higher water uptake (48% vs 73%). In contrast, the cross-linked networks along with the robust metal-organic frameworks prevented the membranes from the excessive swelling ratio (a swelling ratio of 7%). Finally, the robust, porous, and hydrophilic Cr-MIL-101-NH2 frameworks via the construction of well-connected hydrophilic nanochannels significantly enhanced and facilitated hydroxide ion conductivities (0.07 S cm(-1) vs 0.01 S cm(-1) at 30 degrees C). This strategy is a promising method to resolve the trade-off issue between hydroxide ion conductivity and swelling in anion exchange membranes.