关键词: 氢气, 共价有机骨架材料, 吸附, 密度泛函理论, 分子模拟, 化学改性

Abstract:

Covalent organic frameworks (COFs) are considered as a new type of adsorbing material for hydrogen. In this work, density functional theory (DFT) has been applied to investigate the adsorption mechanism of H₂ on seven main clusters of COFs, and GGA/PBE is used in the calculation. The results indicate that the center of benzene ring is the most favorable site when H₂ molecular attacks vertically, in addition the center and oxygen atom of B₃O₃ ring are more favorable when H₂ molecular attacks parallelly. The increase of carbon atom number on organic cluters would be beneficial for adsorption of H₂. By calculation of different adsorption configurations for two H₂ molecules on COF-10 and COF-105, it is found that a cooperative effect between H₂ adsorption on these two COFs could be exist. Doping of alkali metals (Li, Na, K) and substitution of organic functional groups (methyl, sulfhydryl, amino) on COFs can significantly enhance the adsoroption energy, indicating that these chemical modifications are an effective way for enhancement of hydrogen adsorption capacity of COFs.

Key words: hydrogen, covalent organic frameworks, adsorption, density functional theory, molecular simulation, chemical modification