Stable and microporous covalent organic frameworks via weak interactions for gas uptake

Abstract

Covalent organic frameworks are a new class of porous organic polymers that combine excellent stability and well-defined structures. We have designed and constructed two imine COFs (COF–OH and COF–F) with micro-porosity and high stability through the Schiff base reaction. The high porosity and stability of COF–OH are due to intramolecular hydrogen bonding between hydroxyl units with nitrogen atoms in the imine linkage. The fluorine-based COF (COF–F) shows high porosity and stability due to substantial energetic stabilization in the face-to-face stacking interaction on the wall. The COFs also demonstrate high porosity as active platforms for iodine uptake up to 5.71 g g⁻¹ and carbon dioxide uptake up to 3.92 mmol g⁻¹via weak interactions resulting from high porosity and linkages (N atoms) to walls (N, F, and O atoms) in the aromatic skeleton.