A Theoretical and Computational Study of H2 Physisorption on Covalent Organic Framework Linkers and Metalated Linkers: A Strategy to Enhance Binding Strength
Abstract
Hydrogen is deemed as an attractive energy carrier alternative to fossil fuels, and it is required to store for many applications. Physisorption is one of the promising ways to store H2 for its practical applications. Covalent Organic Frameworks (COFs) are promising candidates for H2-storage due to high porosity, surface area and tunable characteristics. To improve the hydrogen physisorption in the COFs, the chelation of transition metals (TM) in the building blocks of the framework has been studied by using first principle-based density functional theory (DFT) method. Here, we report total 96 H2 complexes made of six different COF linkers and chelated with the Sc, Ti and V atoms interacting with up to H2 molecules. The molecular interactions between physisorption H2 and these Sc-, Ti- and V-chelated linkers have been explored in detail. The binding enthalpy of the most complexes is higher than ~10 kJ/mol, which is the basic requirement for practical H2-storage. In the total interaction energy (between physisorption H2 and chelated linkers), the dispersion and electrostatic interactions are dominant. This study is essential in finding out the more efficient COF linkers for practical H2 storage. It can also help to improve the uptake of existing porous materials for H2 storage. The present study paves a way to design transition metal chelated COFs for an effective H2-storage and the knowledge gained from this study is expected to provide some inspiration for developing the corresponding experiments.
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