Covalently Grafting of Ethylenediamine onto a 2D Sub-stoichiometric COF for Enhanced CO₂/N₂ Separation

Abstract

The post-synthetic modification of two-dimensional sub-stoichiometric covalent organic frameworks (COFs) for gas separation, particularly for the efficient removal of CO ₂ from CO ₂/N ₂ mixtures, is an area of growing interest yet remains relatively unexplored. In this study, we report the precise tuning of functional groups in sub-stoichiometric COFs to enhance CO ₂ capture performance. A sub-stoichiometric COF with free aldehyde groups (HPCOF) was designed and synthesized, followed by covalent modification via ethylenediamine (EDA) grafting, yielding HPCOF-EDA. This post-modification strategy significantly increased CO ₂ adsorption capacity (55.7 cm ³·g ^-1 at 298 K and 1 bar) and CO ₂/N ₂ selectivity (58), primarily attributed to the formation of additional N—H···O interactions. These findings demonstrate the potential of functional engineering to broaden the application prospects of sub-stoichiometric COFs in gas adsorption and separation technologies.

Keywords

Covalent organic framework / Sub-stoichiometric / Spatial site-blocking / CO ₂/N2 separation / Dynamic chemistry

RIGHTS & PERMISSIONS

2024 SIOC, CAS, Shanghai, & WILEY-VCH GmbH.