By using the strategy of pre-assembly chlorosulfonation applied to a linker precursor, the first sulfonated zirconium metal-organic framework (JUK-14) with two-dimensional (2D) structure, was synthesized. Single-crystal X-ray diffraction reveals that the material is built of Zr6 O4 (OH)4 (COO)8 oxoclusters, doubly 4-connected by angular dicarboxylates, and stacked in layers spaced 1.5 nm apart by the presence of sulfonic groups. JUK-14 exhibits excellent hydrothermal stability, permanent porosity confirmed by gas adsorption studies, and shows high (>10-4 S/cm) and low (<10-8 S/cm) proton conductivity under humidified and anhydrous conditions, respectively. Post-synthesis inclusion of imidazole improves the overall conductivity increasing it to 1.7×10-3 S/cm at 60 °C and 90 % relative humidity, and by 3 orders of magnitude at 160 °C. The combination of 2D porous nature with robustness of zirconium MOFs offers new opportunities for exploration of the material towards energy and environmental applications.
Keywords: 2D materials; metal-organic frameworks; proton conduction; synthesis; zirconium.
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