Engineering pore limiting diameter of metal–organic frameworks for benchmark separation of mono- and di-branched hexane isomers

The separation of mono- and di-branched hexane isomers remains an important and challenging industrial process for the production of high-octane gasoline. Suitable adsorbents with high adsorption selectivity and capacity are urgently required. Herein, we demonstrate a strategy to realize highly efficient kinetically controlled hexane isomers adsorption separation that utilizes the tunability of the pore limiting diameter in M2TTFTB (M=Zn, Mn, Cd) by metal substitution. The appropriate refinement of the partially contracted pore not only improved the kinetic selectivities, but also enhanced the host–guest interaction and increased the adsorption capacity of 3MP and nHEX. The resulting Mn2TTFTB brought about both the record capacity of 3MP and the record kinetic selectivities of 3MP/22DMB and nHEX/22DMB, exhibiting the largest productivity of high-purity 22DMB in the breakthrough experiments, which sets a new benchmark for the hexane isomers separation via a rarely reported kinetically controlled mechanism.