Synthesis, Structural Characterization, Gas Sorption and Guest-Exchange Studies of the Lightweight, Porous Metal−Organic Framework α-[Mg3(O2CH)6]

• Published in: Inorganic chemistry Vol. 45; no. 14; pp. 5521 - 5528
• Main Authors: Rood, Jeffrey A, Noll, Bruce C, Henderson, Kenneth W
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 10.07.2006
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic060543v

Unsolvated magnesium formate crystallizes upon reaction of the metal nitrate with formic acid in DMF at elevated temperatures. Single-crystal XRD studies reveal the formation of [Mg3(O2CH)6⊃DMF], 1, a metal−organic framework with DMF molecules filling the channels of an extended diamondoid lattice. The DMF molecules in 1 can be entirely removed without disruption to the framework, giving the guest-free material α-[Mg3(O2CH)6], 2. Compound 2 has been characterized by both powder and single-crystal XRD studies. Thermogravimetric analyses of 1 show guest loss from 120 to 190 °C, with decomposition of the sample at approximately 417 °C. Gas sorption studies using both N2 and H2 indicate that the framework displays permanent porosity. The porosity of the framework is further demonstrated by the ability of 2 to uptake a variety of small molecules upon soaking. Single-crystal XRD studies have been completed on the six inclusion compounds [Mg3(O2CH)6⊃THF], 3; [Mg3(O2CH)6⊃Et2O], 4; [Mg3(O2CH)6⊃Me2CO], 5; [Mg3(O2CH)6⊃C6H6], 6; [Mg3(O2CH)6⊃EtOH], 7; and [Mg3(O2CH)6⊃MeOH], 8. Analyses of the metrical parameters of 1−8 indicate that the framework has the ability to contract or expand depending on the nature of the guest present.