Achieving high efficient proton transport in sulfonated poly(arylene ether ketone sulfone)s containing fluorenyl groups by introducing bifunctionalized metal-organic frameworks

In this paper, sulfonated poly(arylene ether ketone sulfone)s containing fluorenyl groups (F-SPAEKS) were synthesized. MIL-101-NH2 was prepared by hydrothermal reaction. The carboxyl group was modified to MIL-101-NH2 by amidation reaction, then difunctional MIL-101-NH2 was designed (MIL-101-NH2-COOH). The fillers of MIL-101-NH2 and difunctional MIL-101-NH2-COOH were added into F-SPAEKS matrix to prepare the hybridized membranes, respectively. The structures and morphologies of MIL-101-NH2, MIL-101-NH2-COOH and hybridized membranes were characterized by SEM, FT-IR, 1H NMR, XPS and XRD. Among these prepared hybridized membranes, FSMNC-4 (the weight percentage of MIL-101-NH2-COOH was 4%) had the highest proton conductivity (159.90 mS cm−1 at 80 °C). The proton conductivity of FSMNC-4 was 1.79 times higher than that of pure F-SPAEKS (89.30 mS cm−1 at 80 °C) and 1.25 times higher than that of FSMN-4 (the weight percentage of MIL-101-NH2 was 4%) (127.55 mS cm−1 at 80 °C), respectively. Meanwhile, the increase of hydrophilic groups also resulted in the highest water absorption of FSMNC-4 (21.57% at 80 °C). The ionic cross-linked networks reduced the swelling ratio of the hybridized membranes. The swelling ratio of all hybridized membranes was lower than 10%. FSMNC-4 also had good thermal and oxidative stability. The open circuit voltage (OCV) and maximum power density of FSMNC-4 were 0.994 V and 466 mW/cm2, respectively. The above results indicated that FSMNC-4 had a promising potential to be applied in PEMFCs.