In this study, a new copper-based metal–organic framework, {[Cu3(μ8-mtif)1.5(DMF)3]·10H2O·4DMF}n (OGU-3), was synthesized using 5,5′-(3-methylthiophene-2,5-diyl)diisophthalic acid (H4mtif) as an organic linker through a solvothermal method. Single-crystal X-ray diffraction analysis revealed that the OGU-3 possesses a three-dimensional porous architecture with a high surface area (2612 m2/g). The framework contains one-dimensional channels along the c-axis with dimensions of approximately 11.26 × 15.48 Å. Gas adsorption measurements demonstrated that the material exhibits a remarkable CH4 uptake capacity, attributed to its large surface area and optimized pore environment. High-pressure CH4 adsorption measurements revealed that OGU-3 exhibits a remarkable gravimetric CH4 uptake of 292.5 cc (STP)/g at 25 °C and 65 bar, representing 5.4% enhancement over its nonmethylated analogue. The findings highlight the potential of thiophene-functionalized ligands in designing high-performance MOFs for efficient CH4 storage applications. This work provides valuable insights into the development of advanced porous materials for energy-related gas storage technologies.