An intrinsically porous trianglimine macrocycle 1 is reported to display energy-efficient and cost-effective adsorptive properties by selectively separating cis-1,2-dichloroethene (cis-DCE) from an equimolar cis- and trans-DCE mixture with a purity of over 96%. The selectivity is enhanced by host/guest C–H⋯π intermolecular interactions. Moreover, the macrocycle can be reused many times without any decrease in performance, which further supports the sustainability of using molecular sieves in chemical separation.