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.