Metal-organic frameworks are materials that have a highly modular synthesis that allows for the choice of ligand, metal, and framework structure for a variety of applications. Targeted modification of metal-organic frameworks via changes in the linker or metal can lead to the tailoring of these materials for specific applications. The well-known framework M2(dobdc) (dobdc4- = 2,5-dioxido-1,4-benzenedicarboxylate), also known as M-MOF-74, possesses a high density of coordinatively unsaturated metal centers that can interact strongly with small gas molecule guests in the framework pores. In this work, a structural isomer of this framework has been synthesized and shown to have altered electronics around the open metal site based on a change in the linker connectivity. This results in a new family of metal-organic frameworks also featuring exposed M2+ cation sites with modified charge density at these sites. H2 was used as a probe to explore the electronic changes in this structural isomer and it was found that low-loading binding enthalpies were higher for a variety of metals (M = Mn, Fe, Co, Ni) relative to the original M2(dobdc) analogs. The techniques of powder x-ray diffraction, powder neutron diffraction, inelastic neutron scattering, infrared spectroscopy, and first-principles electronic structure calculations were collectively used in order to understand the subtle electronic and structural effects that lead to these differences in H2 binding. With this understanding, similar effects could be expected for the binding of other small gas molecules. Further, these results highlight the importance of altering the linker geometry and electronics to selectively modify the properties of metal-organic framework materials in general.

Structural isomer of M<sub>2</sub>(dobdc) with increased charge density and stronger H<sub>2</sub> binding at the open metal sites

248th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.

Structural isomer of M2(dobdc) with increased charge density and stronger H2 binding at the open metal sites

Structural isomer of M₂(dobdc) with increased charge density and stronger H₂ binding at the open metal sites