A new approach of finely tuning multi-nuclear clusters of metal-organic frameworks (MOFs) through symmetry-upgradingly isoreticular transformation was first presented and a bcu-type MOF, {[Cu-4(mu(4)-O)Cl-2(IN)(4)][CuCl2]}(infinity) (NJU-Bai35; NJU-Bai for Nanjing University Bai group), with cluster [Cu-4(mu(4)-O)-Cl-2(COO)(4)N-4] of higher symmetry compared to the pristine MOF, was successfully synthesized. The symmetry upgrading implemented on the inorganic part triggers the adjustment of channels in NJU-Bai35 to fit CO2 molecules, leading to a high CO2 adsorption capacity (7.20 wt % at similar to 0.15 bar and 298 K) and high selectivity of CO2 over N-2 and CH4 (275.8 for CO2/N-2 and 11.6 for CO2/CH4) in NJU-Bai35. Breakthrough experiments further confirmed that NJU-Bai35 might be an excellent candidate for CO2 capture and natural gas purification.