Using structurally defective UiO-66 to construct effective proton conduction path in proton exchange membranes

Water has an important effect on proton conductance process in proton exchange membranes (PEMs). To enlarge the pore size and construct a more efficient water channel, UiO-66 with controllable structural defects were innovatively proposed to blend with SPEEK. Linker defects expose acidic sites, thereby adjusting the hydrophilicity and facilitating the formation of an effective hydrogen bonding network. As a result, S/deU-2 exhibited the highest conductivity under experimental conditions, which was 54.5% higher than that of SPEEK and 31.3% of non-defective UiO-66 filled PEMs. NMR T 2 spectra reviewed that free water, which had the greatest impact on conductivity, accounted for the largest proportion in S/deU-2. In consideration of potential structural weakening due to defect introduction, defect-repair and bioinspired structure optimization strategies were further proposed to balance conductivity and long-term stability. • First study on Zr-based UiO-66 defect density impacting PEM performance. • Improve proton conductivity by 18.9% over bifunctionalized MOFs in PEMs. • Focus on how ‘moderate’ defects enable conductivity, not just their existence. • Expose acidic sites tuning hydrophilicity for effective H-bond networks. • Larger pore size of defective UiO-66 can accommodate more free water molecules.