Efficient purification of ethene by an ethane-trapping metal-organic framework

Separating ethene (C 2 H 4 ) from ethane (C 2 H 6 ) is of paramount importance and difficulty. Here we show that C 2 H 4 can be efficiently purified by trapping the inert C 2 H 6 in a judiciously designed metal-organic framework. Under ambient conditions, passing a typical cracked gas mixture (15:1 C 2 H 4 /C 2 H 6 ) through 1 litre of this C 2 H 6 selective adsorbent directly produces 56 litres of C 2 H 4 with 99.95%+ purity (required by the C 2 H 4 polymerization reactor) at the outlet, with a single breakthrough operation, while other C 2 H 6 selective materials can only produce ca . ⩽ litre, and conventional C 2 H 4 selective adsorbents require at least four adsorption–desorption cycles to achieve the same C 2 H 4 purity. Single-crystal X-ray diffraction and computational simulation studies showed that the exceptional C 2 H 6 selectivity arises from the proper positioning of multiple electronegative and electropositive functional groups on the ultramicroporous pore surface, which form multiple C–H···N hydrogen bonds with C 2 H 6 instead of the more polar competitor C 2 H 4 . The separation of high purity ethene from the mixed gaseous products of cracking poses significant obstacles. Here, the authors present a metal-organic framework which, in contrast to most absorbents, selectively binds the less polar ethane thus allowing the efficient collection of the target product.