A robust indium-organic framework (InOF-15) with open metal sites and Lewis basic sites has been successfully synthesized using a quinoline-based dicarboxylic acid. Moreover, it exhibits high IAST selective CO2 sorption from CO2/CH4 and CO2/N2 mixtures at 273 K, which has been attributed to the coexistence of OMSs and LBSs with strong synergistic effects.