A series of new Nation composite membranes have been prepared by the self-assembly of microporous organic polymer networks (MOPNs) and Nation. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) reveal that MOPNs and Nation membranes have good miscibility affording homogeneous composite membranes Nafion-MOPN-x. Compared with the recast Nation membrane, Nafion-MOPN-x composite membranes show excellent thermal and mechanical properties, good dimensional stability, low methanol permeability, and proper proton conductivity. Also, the passive direct methanol fuel cell (DMFC) of Nafion-MOPN-3 membrane presents a maximum power density of 21.5 mW cm(-2) at 25 degrees C. These results show the introduction of MOPNs can improve the interface compatibility and lessen the cavity problem between fillers and polymeric matrix during chemical blend. Therefore, it casts a new light on developing stable polymer electrolyte membranes (PEMs) for fuel cell application. (C) 2014 Elsevier B.V. All rights reserved,