Temperature-swing molecular exclusion separation of hexane isomers in robust MOFs with double-accessible open metal sites

The separation of hexane isomer mixtures into their individual components is one of the most important while challenging industrial process to produce high-octane gasoline. Herein robust M(pz)[Ni(CN)4], termed MpzNi (M = Co, Ni, pz = pyrazine) that can realize efficient separation of ternary mixtures into the pure, individual components. As optimal pore channels with double-accessible open metal sites providing the adsorbate-dependent affinity differences for molecular exclusion behavior via temperature programming, CopzNi reached optimum performance with not only exceptional selectivity of linear/monobranched alkanes and monobranched/dibranched alkanes, but also notably higher adsorption capacity than those of the previously reported adsorbents. Breakthrough experiments with equimolar ternary C6 alkane isomers and binary branched mixtures confirmed CopzNi can highly capture n-hexane and 2-methylpentane from their mixtures. The excellent separation efficiency, lower-energy regeneration, scalability, recyclability as well as high stability render the CopzNi a benchmark candidate for implementation in the current separation processes.