Triptycene, Phenolic-OH, and Azo-Functionalized Porous Organic Polymers: Efficient and Selective CO₂ Capture

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 (−N═N−) 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.