Synthesis and Characterization of Covalent Triazine Frameworks Based on 4,4′-(Phenazine-5,10-diyl)dibenzonitrile and Its Application in CO2/CH4 Separation

Covalent triazine frameworks (CTFs) have gained recognition as stable porous organic polymers, for example, for CO2 separation. From the monomer 4,4′-(phenazine-5,10-diyl)dibenzonitrile (pBN), new pBN-CTFs were synthesized using the ionothermal method with a variation in temperature (400 and 550 °C) and the ZnCl2-to-monomer ratio (10 and 20). N2 adsorption yielded BET surface areas up to 1460 m2g −1. The pBN-CTFs are promising CO2 adsorbents and are comparable to other benchmark CTFs such as CTF-1 with a CO2 uptake of pBN-CTF-10-550 at 293 K of up to 54 cm3 g−1 or 96 mg g−1, with a CO2/CH4 IAST selectivity of 22 for a 50% mixture of CO2/CH4. pBN-CTF-10-400 has a very high heat of adsorption of 79 kJ mol−1 for CO2 near zero coverage in comparison to other CTFs, and it also stays well above the liquefaction heat of CO2 due to its high microporosity of 50% of the total pore volume.