A family of heterometallic NbU-3-Mn/M-III compounds were synthesized through postsynthetic exchange of Mill ions of a pentanuclear Mn-II-based metal-organic framework (NbU-3-Mn, where NbU denotes Ningbo University) for enhancing the gas separation performance. Significantly, NbU-3-Mn/Fe has a C2H2/CO2 separation selectivity similar to that of NbU-3-Mn but exhibits enhanced dynamic separation of C2H2/CO2, which was proven by breakthrough experiments.