A highly robust heterometallic (CoLa2III)-La-II-organic framework (NUC-19) is synthesized and features 1D rectangle-like channels with a window size of 3.4 X 6.3 angstrom(2) and a carboxyl-group-modified inner surface. NUC-19 exhibits significantly differential uptake for C2H2, C2H4, and CH4, and the ideal adsorbed solution theory selectivities of C2H2/C2H4 (1:99, v/v) and C2H2/CH4 (50:50, v/v) at room temperature can reach up to 4.0 and 79.7, respectively. Fixed-bed dynamic breakthrough experiments under simulated industrial conditions indicate that NUC-19 could efficiently trap C2H2 from mixed gases of C2H2/CH4 and C2H2/C2H4.