A vinyl-pedant triazine-based covalent organic framework for efficient C3H6/C2H4 separation

The separation of propylene (C3H6) and ethylene (C2H4) during the methanol-to-olefin (MTO) process is crucial yet challenging. Herein, we report a covalent organic framework (TzDva) featuring favorable nitrogen adsorption sites and vinyl modification for the capture of C2H4 from C3H6/C2H4 mixtures. TzDva exhibits enhanced crystallinity and porosity as well as reduced pore size compared to its vinyl-free counterpart (TzPA), as revealed through comprehensive characterization. The excellent performance of TzDva for C3H6/C2H4 separation combined with its excellent recyclability was confirmed by both static adsorption and dynamic breakthrough experiments. Particularly, it exhibits a C2H4 productivity of 4.29 mmol·g–1 at 298 K with C3H6/C2H4 (10/90) mixture. With decreasing temperature to 273 K, the performance can be further enhanced. Theoretical calculations and in-situ infrared analysis suggested that the remarkable selectivity of TzDva towards C3H6 stems from its favorable pore environment, which facilitates a greater number of interactions with C3H6 compared to C2H4 guests. These results underpinned the effective separation of gas mixtures relevant to the MTO process.