Sulfur hexafluoride (SF6), which has a greenhouse effect of 228 000 times more terrible than carbon dioxide, has attracted increasing attention. Its efficient capture, especially from the mixtures with low SF6 concentrations, is urgently needed while challenging. Herein, we use a calcium (Ca)-based metal–organic framework (MOF; SBMOF-1) with multiaromatic ring-functionalized channels to achieve a record selectivity as high as 727 for an industrially relevant SF6/N2 mixture (volume concentration of SF6: 0.03%) at 298 K and 1 bar. Grand canonical Monte Carlo simulations and density functional theory calculations identified that SF6 molecules were energy-favorably trapped in the functionalized MOF channels by the strong interactions between the channel walls and six fluorine atoms on SF6. Excellent breakthrough results accompanied with good stability and regenerability recommend its promising application for practical SF6 capture from low-concentration SF6 mixtures, which also provides a new benchmark for SF6/N2 separation.