Jump to main content
Jump to site search


Investigation of the Effect of Polar Functional Groups on the Crystal Structures of Indium MOFs

Abstract

Three new In-MOFs with -NH2 and/or -NO2 functionality are reported using 2-amino- (H2BDC-NH2), 2-nitro- (H2BDC-NO2) and 2-amino-5-nitroterephthalic acid (H2BDC-NH2/NO2). Their structures were determined from single crystal X-ray diffraction data. The structure of the first In-MOF of composition [In(BDC-NH3)(BDC-NH2)]∙1.6DMF∙1.9H2O (In-BDC-NH2; DMF is dimethylformamide; space group P6222, a = b = 14.738(2) Å, c = 12.257(3) Å) is build up by two interpenetrating nets of InO8 polyhedra interconnected by BDC-NH22- ions to form a framework with qtz topology. Charge balance is accomplished by partial protonation of the amino group, which was confirmed by IR spectroscopy. The interpenetration leads to a decrease of the pore dimension (4.4 Å in diameter). Thermogravimetric analysis revealed stability up to 300 °C. Replacement of H2BDC-NH2 by H2BDC-NO2 in the reaction mixture led to the isoreticular MOF containing no -NO2 groups but exclusively un- and amino-functionalized linkers. Hence an indium mediated reduction of the H2BDC-NO2 linker molecule during solvothermal synthesis has occurred. The use of H2BDC-NH2/NO2 under exactly the same reaction conditions did not result in the formation of a MOF, but changing the synthesis parameters, a new -NH2/-NO2 bifunctionalised In-MOF of composition (DMA)2[In3(O)(BDC-NH2/NO2)4.5]∙DMF (DMA is dimethylammonium), denoted In-BDC-NH2/NO2 was obtained. The crystal morphology can be altered from cubic to truncated octahedral crystals by varying the DMF/ethanol volume ratio during synthesis. The compound crystallises in the cubic space group I-43m, a = 24.8947(1) Å, and the framework contains trinuclear {In3(µ3-O)} clusters which are interlinked by the BDC-NH2/NO22- ions to form super-tetrahedra. Four face-sharing super-tetrahedra form ultra-tetrahedra which are connected to form the final cubic framework with ncb topology and isolated inaccessible pores.

Back to tab navigation

Supplementary files

Publication details

The article was received on 07 Jun 2017, accepted on 07 Jul 2017 and first published on 10 Jul 2017


Article type: Paper
DOI: 10.1039/C7CE01067B
Citation: CrystEngComm, 2017, Accepted Manuscript
  •   Request permissions

    Investigation of the Effect of Polar Functional Groups on the Crystal Structures of Indium MOFs

    M. Krueger, M. Albat, A. K. Inge and N. Stock, CrystEngComm, 2017, Accepted Manuscript , DOI: 10.1039/C7CE01067B

Search articles by author

Spotlight

Advertisements