We propose for the first time an acetic acid (AcOH)-fragmented linker co-assembly strategy to create mesoporous defects in a microporous metal-organic framework (MOF), HKUST-1. By using various methods, including 1H NMR, FT-IR and XPS, we confirmed the successful co-assembly of AcOH fragments into the HKUST-1 structure. The prepared AcOH-fragmented HKUST-1 materials showed improved methane uptake (13% higher storage capacity at 65 bar and 16% higher deliverable capacity between 65 bar and 5 bar) and greatly increased surface areas (from 1787 to 2396m(2)/g) and pore volumes (from 0.77 to 1.20 cc/g) compared to the parent HKUST-1. This is remarkable because HKUST-1 is considered to be one of the most promising materials for methane storage. Furthermore, we propose possible scenarios of defect formation in the AcOH-fragmented HKUST-1 materials from simulations of several hypothetical structures. This AcOH-fragmented linker co-assembly strategy could be compatible with a large number of carboxylate-based MOFs.