A non-interpenetrated anionic In-MOF (FJU-302) based on a linear H₂bpdc and an angled H₂cdc as dual-ligands was characterized by FT-IR, TGA and X-ray single-crystal/powder diffraction. FJU-302 crystallizes in the monoclinic system and I4₁/amd space group with a = 27.1274(8), b = 27.1274(8), c = 29.788(3) Å, V = 21921(2) ų, Z = 16, M_r = 608.32, D_c = 0.737 g/cm³, F(000) = 4848, μ(CuKα) = 3.659 mm^–1, R = 0.0800 and wR = 0.1911 for 5703 observed reflections (I > 2s(I)), and R = 0.1470 and wR = 0.2342 for all data. In this work, a carbazole based anionic In-MOF (FJU-302) was designed and synthesized, and the proton conductivity from subzero temperature (–30 °C) to 70 °C was measured without additional humidity. FJU-302 presents a max proton conductivity of 6.47 × 10^–4 S·cm^–1 at 70 °C, and it can maintain 5.88 × 10^–7 S·cm^–1 at –30 °C. This work reports a first carbazole based MOF for proton conductivity at subzero temperature conditions.