Introduction of Bifunctionalized UIO-66-NH2 for Highly Conductive and Long-Term Stable Fluorene-Based Sulfonated Poly(aryl ether ketone sulfone) PEMs

In this paper, UiO-66-NH2 was successfully modified with a phosphate group by a Schiff base reaction. The phosphate and amine bifunctionalized UiO-66-NH2 (PUIN) was successfully prepared. A series of composite membranes were prepared by adding PUIN fillers to sulfonated poly(aryl ether ketone sulfone) (FSPUIN-X) containing fluorene groups. The introduction of PUIN containing both phosphate and amino bifunctional groups increased the number of proton transport sites within the membrane and facilitated the construction of continuous proton transport channels. The addition of PUIN resulted in a significant increase in the proton conductivity of FSPUIN-X due to the introduction of more proton transport sites. The conductivity of FSPUIN-5 (174.22 mS cm–1) was 1.46 times higher than that of pure membranes (119.32 mS cm–1) at the same condition. And the open-circuit voltage and power density of FSPUIN-5 also reached 0.957 V and 0.54 W cm–2, respectively. The structure and morphology of PUIN and membranes were characterized by Fourier infrared (FT-IR), X-ray polycrystalline diffraction (XRD), nuclear magnetic resonance hydrogen spectrum (1H NMR), and scanning electron microscopy (SEM). Meanwhile, the PUIN also strengthened the mechanical properties of FSPUIN-X series membranes. All of the results indicated that the introduction of phosphate and amine bifunctionalized UiO-66-NH2 promoted the comprehensive performance of the composite membranes.