Covalent triazine frameworks for the dynamic adsorption/separation of benzene/cyclohexane mixtures

Abstract

The development of nanoporous organic frameworks with excellent physicochemical stability, high selectivity, and simple processability have increasingly fulfilled the urgent need for adsorbents used in the cost-effective and energy-efficient separation of benzene (Bz) and cyclohexane (Cy) vapor mixtures. Covalent triazine frameworks (CTFs) represent particularly promising adsorbents for these applications. However, CTFs synthesized via highly advantageous Friedel–Crafts reactions with low reaction temperature and short polymerization time have been rarely reported. The present work addresses this issue by synthesizing three CTFs, denoted as CCTF-1, CCTF-2, and CCTF-3 with cycloaliphatic moieties and progressively decreasing total pore volumes, via Friedel–Crafts reactions from 9,9′-spirobifluorene, triptycene, and 1,3,5,7-tetraphenyladamantane precursors, respectively, in conjunction with cyanuric chloride. The adsorption isotherms of single component Bz and Cy vapors demonstrate that the uptake of both vapors increases with increasing total pore volume, while the dynamic breakthrough curves obtained with CCTF-1 at a temperature of 298 K and relative pressures of 0.95 present Bz and Cy vapor uptakes of 878 mg g⁻¹ and 441 mg g⁻¹, respectively. These results verify that the synthesized CTFs can separate Bz/Cy vapor mixtures efficiently.