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 –NH 2 and –SO 3 H, 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.