Different contents of metal-organic framework (3, 5, 7, 10 and 12 wt. % and MOF is HKUST-1) were incorporated into cyclohexane dicarboxylic acid based polybenzimidazole (Cy-PBI). In the composite membranes, the interaction between MOF and PBI polymer resulted in peak broadening as observed in FTIR spectra (2000–3000 cm⁻¹). The recorded proton conductivity of CM-7 at 160 °C (224 mS/cm) was almost two fold to that of pristine PBI membrane (114 mS/cm and surprisingly high mechanical strength was displayed (Tensile modulus: 671 MPa, elongation 69% under doped condition). Minimum swelling behavior and high doping level gives the evidence that acid molecules (proton carriers) are housed within the MOF cavities those would act as proton hopping centres. The FESEM images of the composite membrane (CM-7) displayed a uniform distribution of MOF within the matrix, complementing the enhanced properties observed. This work exemplifies the mediating role of MOF in improving the conductivity of PBI membranes.