Highly Selective Separation of Hydrogen Isotopes via the Construction of Ionic-Bonded Organic Frameworks

Separation of hydrogen isotopes is a great challenge due to the almost identical physicochemical properties of the two isotopes. Recently, crystalline organic frameworks have demonstrated the potential to separate hydrogen isotopes by kinetic quantum sieving, but the synthesis of porous frameworks with ultrafine pores remains a significant challenge for D2/H2 separation. In this work, ionic-bonded organic frameworks (IOFs) were synthesized using tetraphenylethylene (TPE)-based multidentate imidazolium cations and sulfonic anions as self-building blocks via a cation−π interaction-assisted strategy to construct ionic-bonding directionality. This structural formation mechanism is obviously different from the previously reported hydrogen-bonding-assisted and sterically induced ionic orientation of crystalline porous organic salts. These synthesized IOFs, which exhibit distinct pores and high surface areas, have great potential as quantum sieves for the separation of hydrogen isotopes (H2 and D2), as evidenced by an unprecedented high D2/H2 selectivity of 12.7 via the kinetic quantum sieving effect.