A Quantum Study of Dihydrogen Binding to The Lithium Alkoxide Doped Covalent Organic Framework-105

Abstract

The adsorption properties of multiple hydrogen molecules (1-5 molecules) bound with the COF-OLi structure were predicted by the B3LYP/6-311G(d,p) and ONIOM(B3LYP/6-311G(d,p):AM1) methods. The MP2/6-311G(d,p) method in conjunction with basis set superposition error (BSSE) was also employed for evaluating adsorption energies of the (H₂)_n-COF-OLi complexes (n = 1-5). It was found that the ONIOM(B3LYP/6-311G(d,p):AM1) level of theory appropriates to characterize hydrogen adsorptions on the COF-OLi structure. The adsorption energy of the H₂-COF-OLi complex obtained from the MP2/6-311G(d,p) method including BSSE correction is −2.51 kcal/mol, while corresponding energy of −4.27 kcal/mol was evaluated for two molecules of hydrogen. In the case of three hydrogen molecules, the adsorption energy of −5.61 kcal/mol is obtained, which is weaker than that of −6.37 kcal/mol calculated from the (4H₂)-COF-COF-OLi complex. Finally, the strongest adsorption energy of −7.12 kcal/mol was predicted for five hydrogen molecules. [DOI: 10.1380/ejssnt.2012.203]