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 variation of temperature (400 and 550 °C) and 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, having 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, which also stays well above heat of the liquefaction heat of CO2 due to its high microporosity of 50% of the total pore volume.