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 Zr6O4(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.
