Computer-Aided Design of Interpenetrated Tetrahydrofuran-Functionalized 3D Covalent Organic Frameworks for CO2 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 3R,4R-diaminotetrahydrofuran as the link. Subsequently, the adsorption capacity of CO2 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 (similar to 4.6 mmol/g). At lower pressure, the more stable 5-fold interpenetrated framework showed higher uptake due to stronger interaction of CO2 with the framework. The contribution of framework charges to CO2 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 CH2 group. Although no change was observed in the 1-fold framework, the CO2 capacity at 1 bar decreased by similar to 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 CO2 adsorption.