Two isostructural copper-based metal-organic frameworks (UPC-55 and UPC-56) were synthesized via a solvothermal reaction using methoxy-functionalized tricarboxylic acid ligands and copper nitrate. Their structures and stability were characterized and tested through single-crystal X-ray diffraction, thermogravimetric analysis, and infrared spectroscopy. It is found that the treatment of methoxy functional groups makes UPC-55 and UPC-56 exhibit selective adsorption of C₂H₂. Due to differences in functional group positioning, their adsorption separation capabilities vary slightly. At 298 K, the adsorption of C₂H₂ by UPC-55 and UPC-56 are 31.8 cm³/g and 52.2 cm³/g. The equal proportional C₂H₂/CO₂ separation ratios are 3.508 and 5.345, respectively.