Porous organic cages for efficient gas selective separation and iodine capture

The enantiomeric porous organic cages, (R)/(S)-BTPOC, have been devised and prepared by means of dynamic covalent chemistry, using imine bond formation between bithiophene-based tetraaldehyde and cyclohexanediamine building blocks. These two cage molecules with porous interiors, stable aromatic backbones, and multiple electron-rich building units have been fully characterized by spectroscopy and single crystal X-ray diffraction studies. Self-assembly of BTPOC molecules provided porous crystalline materials with high CO2 adsorption of 265 cm3 g−1 under 760 mmHg and 196 K according to the physical gas sorption analysis. The guest-free cage shows distinct CO2, CH4, and N2 adsorption behaviors. Moreover, BTPOC is able to accommodate a large amount of I2 with a high uptake value of 3.21 g g−1, superior to almost all the porous molecular crystals reported thus far. This stable material has also excellent recyclability, keeping above 85% capacity when being activated for the fourth cycles. Mechanism investigations reveal the close association of the good adsorption ability with the abundant porosity, π-conjugated network structure, and high imine bonds content. The present work shows the great application potentialities of these microporous POCs.