Crystal engineering of porous coordination networks to enable separation of C2 hydrocarbons

, x = 2, 4, 6). This situation is rapidly changing thanks to PCN sorbents that have set new performance benchmarks for several C2 separations. Herein, we review and analyse PCN sorbents with respect to the supramolecular chemistry of sorbent-sorbate binding and detail the crystal engineering approaches that have enabled the exquisite control over pore size and pore chemistry that affords highly selective binding sites. Whereas the structure-function relationships that have emerged offer important design principles, several development roadblocks remain to be overcome.