Computer-Aided Design of Interpenetrated Tetrahydrofuran-Functionalized 3D Covalent Organic Frameworks for CO<sub>2</sub> Capture

Using computer-aided design, several interpenetrated imine-linked 3D covalent organic frameworks with diamondoid structures were assembled from tetrakis-4-formylphenylsilane as the tetrahedral node, and 3<i>R</i>,4<i>R</i>-diaminotetrahydrofuran as the link. Subsequently, the adsorption capacity of CO<sub>2</sub> in each framework was predicted using grand canonical Monte Carlo simulations. At ambient conditions, the 4-fold interpenetrated framework, with disrotatory orientation of the tetrahedral nodes and diaxial conformation of the linker, displayed the highest adsorption capacity (∼4.6 mmol/g). At lower pressure, the more stable 5-fold interpenetrated framework showed higher uptake due to stronger interaction of CO<sub>2</sub> with the framework. The contribution of framework charges to CO<sub>2</sub> uptake was found to increase as the pore size decreases. The effect of functional group was further explored by replacing the ether oxygen with the CH<sub>2</sub> group. Although no change was observed in the 1-fold framework, the CO<sub>2</sub> capacity at 1 bar decreased by ∼32% in the 5-fold interpenetrated framework. This work highlights the need for a synergistic effect of a narrow pore size and a high density of ether-oxygen groups for high-capacity CO<sub>2</sub> adsorption.