Methanol crossover is still a significant barrier to the commercialization of direct methanol fuel cells with wide-used Nafion (R) membrane. Herein, molecular sieve is introduced into the design of polymer electrolyte membrane to alleviate methanol crossover. The UZM-9 zeolite with an intermediate window size of 0.42 nm can effectively separate hydrated methanol (ca. 1.10 nm) and hydrated proton (ca. 0.23 nm). The methanol diffusion rate through the membrane is effectively suppressed after modified with UZM-9, which is about four times lower than the origin Nafion (R) membrane. The resulted peak power density reached 80 mW cm(-2) with 2 mol L-1 methanol solution feed, which is 2.5-fold higher than that of direct methanol fuel cell with commercial Nafion (R) membrane. These results open a promising route to alleviate methanol crossover in direct methanol fuel cells. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.