First-principle study on the lattice-directed missing linker defect in zirconium based metal-organic framework (MOF-801): Electronic properties and interaction with hydrogen

The nature of defects in metal-organic frameworks (MOFs) due to missing linker has been studied using first-principle approach based on periodic density functional theory (DFT). MOF-801 as zirconium-based MOFs is investigated in this study due to its densely packed structure where a zirconium node is coordinated with twelve fumarate ligands. In this study, the missing linker defect was formed by removing fumarate ligand in each lattice direction and the energy is compared. The removal of one fumarate ligand in each lattice direction seems to have relatively homogenous energy distribution with small energy differences when the defect sites are capped with formate HCOO- (FA), chloride (Cl-), hydroxide (OH-) ions, OH- plus H2O and Cl- plus H2O according to the HSE06 calculations. The electronic properties of defective MOF-801 have shown that removing a fumarate ligand decreases the bandgap energy by small fraction which can be further identified from the density of states. The application of defective MOF-801 was also tested for hydrogen adsorption. The adsorption energy indicates that the presence of defect might increase the affinity of MOF-801 for hydrogen storage in certain binding sites. This study shows further understanding about the nature of defect due to missing linker in densely packed MOF-801 and its prospect for hydrogen storage