Molecular Engineering for Organic Cage Frameworks with Fixed Pore Size to Tune Their Porous Properties and Improve CO₂ Capture

Organic cage frameworks (OCFs), one kind of amorphous porous organic polymers with fixed pore size, exhibit great potential in molecular separations and sensing. However, it is a great challenge to control the porous properties of OCFs because of the low yielding for synthesizing the highly stable organic cage monomers. Herein, two organic cage frameworks (OCFs) pCage-1 and pCage-2 were constructed from bicyclooxacalixarene cages Cage-1 and Cage-2, respectively. The pore sizes of both the frameworks pCage-1 and pCage-2 were 5.4 Å because their monomers Cage-1 and Cage-2 have similar intrinsic cavities. Compared with the framework pCage-1, pCage-2 shows significant improvement in porous properties, including the Brunauer–Emmett–Teller (BET) surface area, CO2 adsorption capacity, and adsorption selectivity of CO2/N2, which may be the reason for the introduction of N-doped triazine unit.