Natural gas is increasingly being viewed as one of the most viable alternatives to gasoline. However, its vehicular application will only be widespread if safe and high-capacity methane stores are developed. In this work, we report an over 33% increase in methane uptake on a post-synthetically modified metal–organic framework. The underlying mechanism for this dramatic increase is due to lattice defects formed upon post-synthetic modification. This method may open new approaches to natural gas storage.