In this study, the preparation and characterization of a new ternary nanocomposite polymer electrolyte membrane containing sulfonated PSU, MOF and silica nanoparticles were investigated as a polymer electrolyte membrane. The encapsulation of imidazole in NH2MIL-53(Al) and sulfonic acid functionalization of silica have been developed to produce proton-conducting nanoparticles. In addition, photo grafting polymerization of AMPS from PSU and sulfonation of PSU backbone was designed to prepare PSU chains bearing sulfonic acid groups. The embedding of MOF/Si nanoparticles resulted in significant improvement of the mechanical and thermal properties of the prepared membranes. According to the result of proton conductivity, proton transport of the prepared nanocomposite membrane increases to 17 mS cm(-1) by adding only 5% of sulfonic acid functionalized silica and imidazole-encapsulated MOF nanoparticles (at 70 degrees C). Also, this nanocomposite membrane showed a power density as high as 40.80 mW cm(-2) at peak current density of 10030 mA cm(-2). The thermal and mechanical properties of these nanocomposite membranes were also studied. (C) 2018 Elsevier Ltd. All rights reserved.