Microporous Metal–Organic Framework with a Completely Reversed Adsorption Relationship for C₂ Hydrocarbons at Room Temperature

As a new type of porous material, metal-organic frameworks (MOFs) have been widely studied in gas adsorption and separation, especially in C₂ hydrocarbons. Considering the stronger interaction between the unsaturated molecules and the metal sites, and the smaller molecular size of unsaturated molecules, the usual relationship of affinities and adsorption capacities among C₂ hydrocarbons in most common MOFs is C₂H₂ > C₂H₄ > C₂H₆. Herein, a unique microporous metal-organic framework, NUM-7a (activated NUM-7), with a completely reversed adsorption relationship for C₂ hydrocarbons (C₂H₆ > C₂H₄ > C₂H₂) has been successfully synthesized, which breaks the traditional concept of the adsorption relationship of MOFs for C₂ hydrocarbons. Based on this unique adsorption relationship, a green and simple one-step separation purification for a large amount of C₂H₄ can be expected to be achieved through the selective adsorption of C₂H₆. In addition, NUM-7a also shows good selectivities in C₂H₂/CO₂ and CO₂/CH₄.