Theoretical studies on pillared covalent organic frameworks for a hydrogen storage material

Pillared covalent organic frameworks (PCOFs) have been studied with density functional theory (DFT) calculations. Based on the covalent organic framework-1 (COF-1) structure, one of the COFs synthesized by using the condensation reactions of phenyl diboronic acid {C₆H₄[B(OH) ₂]₂}, we inserted pillar molecules between the organic layers to improve the physisorption ability for hydrogen molecules. Pyridine, pyrazine and 1,4-diaza-bicyclo[2.2.2]octane (DABCO) could be considered as the candidates for the pillar molecules and pyridine wad used as the pillar in this study. The binding sites and the orientations of the pillar molecules were investigated on cluster models of COFs. From the calculations, we observed puckering in the cluster model of the COF, which were caused by binding of pyridine molecules.