Triptycene, Phenolic-OH, and Azo-Functionalized Porous Organic Polymers: Efficient and Selective CO₂Capture

The well-known azo coupling reaction was utilized to yield a new group of triptycene-derived azo polymers (TAPs) bearing phloroglucinol units. TAPs have hierarchical porosity (presence of micropores and mesopores) and are thermally stable. TAPs have moderate surface area (SABET up to 772 m2 g-1) but demonstrate rather high CO2 uptake (up to 150 mg g-1). Azo functional group is reportedly N2-phobic and hence porous organic polymers (POPs) with azo (-NN-) units show high CO2/N2 selectivity. TAPs register CO2/N2 selectivity (273 K) that is higher than most azo-POPs reported until date. This favorable property of TAPs is attributed to the simultaneous coexistence of triptycenes (aromatic and three-dimensional rigid with high internal free volume), phenolic-OH (polar and CO2-philic), and azo (CO2-philic and N2-phobic) functional groups in the polymeric framework.