Optimizing CO2 capture and separation in pyrene derived covalent triazine frameworks

Abstract

Covalent triazine framework (CTF) is widely utilized in lots of porosity related applications such as gas storage, molecule separation and heterogenous catalysis. The permanent porosity and high nitrogen content in the CTF material will greatly promote the affinity between gas molecules and the skeleton. In this work, four covalent triazine framework materials (denoted as Py-CTF-400, Py-CTF-500, TPPy-CTF-400 and TPPy-CTF-500) with high BET surface areas had been successfully constructed by pyrene-based building block under ionothermal reaction conditions using anhydrous ZnCl2 as the polycyclotrimerization catalyst. The surface area, pore volume/size of CTFs can be simply tuned by varying the synthesis temperature. Among the four CTFs, TPPy-CTF-400 display high specific surface area up to 1753 m2/g. The high surface area and nitrogen rich scaffold enable these CTFs to facilitate in CO2/N2, CO2/CH4 separation. Impressively, the CO2/N2 selectivity of Py-CTF-500 is up to 45.3 (298 K, 1 bar), which is comparable to the highest value calculated by ideal adsorption solution theory (IAST) among CTF based materials. More importantly, as the building units of these CTFs extending from 1,3,6,8-tetracyanopyrene (TPy) to 1,3,6,8-tetrakis(4-cyanophenyl) pyrene (TPPy), their CO2/N2, CO2/CH4 separation efficiency decreased, which is probably ascribed to the decrescent size of the corresponding pore aperture.