Using bifunctionalized NH2-UiO-66-SO3H to improve the performance of sulfonated poly (ether ether ketone) in proton exchange membranes

Blending metal-organic frameworks to optimize proton transport pathways is one of the strategies to improve the proton conductivity of proton exchange membranes (PEM). In this paper, amino-sulfonic acid bifunctionalized UiO-66 (NUS) by one-pot solvothermal method is synthesized, and sulfonated poly (ether ether ketone)/NUS-X (SPEEK/NUS-X) hybrid membranes are prepared by mixing NUS into SPEEK matrix. Among them, SPEEK/NUS-1.5 has the highest proton conductivity (177.76 mS cm−1, 70 °C, 100% RH) and maintain a 300 h conductivity stability. And its maximum power density was 423.2 mW cm−2, exceeding pristine SPEEK by 2.20 times. Compare to the pristine SPEEK membrane, it is interesting to note the disappearance of SAXS scattering peak of SPEEK/NUS-1.5. It is speculated that this phenomenon was caused by the generation of acid-base pairs between –NH2 and –SO3H, and the improved hydrogen bonding network provides more proton transport channels and immobilizes sulfonic acid groups for improved durability. The resultant proton conductivity is stable over 300 h with about 90% retention.