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Following the concept of isoreticular chemistry, we carried out a systematic study on Ga-containing metal–organic frameworks (MOFs) using six V-shaped linker molecules of differing sizes, geometries, and additional functional groups. The linkers included three isophthalic acid derivatives (m-H2BDC-R, R = CH3, OCH3, NHCOCH3), thiophene-2,5-dicarboxylic acid (H2TDC), and two 4,4′-sulfonyldibenzoic acid derivatives (H2SDBA, DPSTA). The crystal structures of seven compounds were elucidated by a combination of model building, single-crystal X-ray diffraction (SCXRD), three-dimensional electron diffraction (3D ED), and Rietveld refinements against powder X-ray diffraction (PXRD) data. Four new Ga-MOFs that are isoreticular with their aluminum counterparts, i.e. Ga-CAU-10-R (Ga(OH)(m-BDC-R); R = OCH3, NHCOCH3), Ga-CAU-11 (Ga(OH)(SDBA)), and Ga-CAU-11-COOH (Ga(OH)(H2DPSTC)), were obtained. For the first time large single crystals of a MOF crystallizing in the CAU-10 structure type could be isolated, i.e. Ga-CAU-10-OCH3, which permitted a detailed structural characterization. In addition, the use of 5-methylisophthalic acid and thiophene-2,5-dicarboxylic acid resulted in two new Ga-MOFs denoted Ga-CAU-49 and Ga-CAU-51, respectively, which are not isostructural with any known Al-MOF. The crystal structure of Ga-CAU-49 ([Ga4(m-HBDC-CH3)2(m-BDC-CH3)3(OH)4(H2O)]) contains an unprecedented rod-shaped inorganic building unit (IBU) of the formula ∞1{Ga16(OH)18O60}, composed of corner-sharing GaO5 and GaO6 polyhedra. In Ga-CAU-51 ([Ga(OH)(C5H2O2S)]) chains of alternating cis and trans corner-sharing GaO6 polyhedra form the IBU. A detailed characterization of the title compounds was carried out, including nitrogen gas and water vapor sorption measurements. Ga-CAU-11 was the only compound exhibiting porosity toward nitrogen with a type I isotherm, a specific surface area of aS,BET = 210 m2/g, and a micropore volume of Vmic = 0.09 cm3/g. The new MOF Ga-CAU-51 exhibits exceptional water

A new layered mesoporous Zr-MOF of composition [Zr30O20(OH)26(OAc)18L18] was synthesized by employing 5-acetamidoisophthalic acid (H2L) using acetic acid as the solvent. The new MOF, denoted as CAU-45, exhibits a honeycomb structure of stacked layers which comprise both hexa- and dodecanucelar zirconium clusters. Its structure was solved from submicrometer-sized crystals by continuous rotation electron diffraction (cRED). Liquid phase exfoliation and size selection were successfully performed on the material.

Electron and powder diffraction were combined to elucidate the structure of the new coordination polymer [Sc-2(FcDC)(3)] based on 1,1'-ferrocenedicarboxylate (FcDC(2-)), denoted as CAU-50. Remarkably, three different conformers of the very same linker molecule are observed, two of which serve as connectors for the scandium cations while one conformer acts as capping agent.

A new scandium naphthalenedicarboxylate with the framework composition [Sc-2(1,4-NDC)(3)] (H-2-1,4-NDC = 1,4-naphthalenedicarboxylic acid) was obtained under hydrothermal synthesis conditions. A structure model could be developed by a combination of 3D electron diffraction measurements and computationally assisted structure determination, which was further validated by a good agreement with the experimental powder X-ray diffraction pattern. The structure consists of isolated ScO6 octahedra interconnected by the carboxylate groups of linker molecules to form chains. These chains are connected by the naphthalene-moieties to form a three-dimensional framework with square-shaped pores and the organic group pointing into the pores. Although very similar synthesis conditions were chosen, [Sc-2(1,4-NDC)(3)] is not isostructural to aluminum naphthalenedicarboxylate [Al(OH)(1,4-NDC)], which crystallizes in a MIL-53 type structure. This can be traced back to the different inorganic building units that are observed. The compound was thoroughly characterized by elemental analysis, IR spectroscopy, sorption measurements, thermogravimetric analysis and luminescence measurements. [Sc-2(1,4-NDC)(3)] exhibits a high thermal stability and a ligand-based blue luminescence in the solid state at room temperature.

Two new scandium-containing coordination polymers, with the formulae {(CH3)2NH2}[Sc(BPDC)2] (1) and [Sc(OH) (BPyDC)] (2) were solvothermally synthesized by using the linear linker molecules biphenyl-4,4′-dicarboxylic acid (H2BPDC) and 2,2′-bipyridine-5,5′-dicarboxylic acid (H2BPyDC). Crystal structures were determined from single-crystal and powder Xray diffraction data, respectively. The crystal structures of 1 and 2 contain isolated ScO6 or chains of trans corner-sharing ScO6 octahedra as the inorganic building unit (IBU), which are connected by the linker molecules to a 3D framework or a layered structure, respectively. The compounds were characterized by IR-spectroscopy, elemental analysis, thermogravimetric analysis and photoluminescence spectroscopy. 1 shows blue emission at 400 nm, while 2 exhibits intense green emission at 550 nm with a high quantum yield (QY) of 69 %.

The metallocene-based linker molecule 1,1'-ferrocenedicarboxylic acid (H(2)FcDC) was used to synthesize four different polymorphs of composition [In(OH)(FeC12H8O4)]. Using conventional solvent-based synthesis methods and varying the synthetic parameters such as metal source, reaction temperature, and solvent, two different MOFs and one ID-coordination polymer denoted as CAU-43 (1), In-MIL-53-FcDC_a (2), and InFcDC (3) were obtained. Furthermore, thermal treatment of CAU-43 (1) at 190 degrees C under vacuum yielded a new polymorph of 2, In-MIL-53-FcDC_b (4). Both MOFs 2 and 4 crystallize in a MIL-53 type structure, but in different space groups C2/m for 2 and P (1) over bar for 4. The structures of the four title compounds were determined by single-crystal X-ray diffraction (SCXRD), powder X-ray diffraction (PXRD), or a combination of three-dimensional electron diffraction measurements (3D ED) and PXRD. N-2 sorption experiments of 1, 2, and 4 showed specific surface areas of 355 m(2) g(-)(1), 110 m(2) g(-1), and 140 m(2) g(-)(1), respectively. Furthermore, the electronic properties of the title compounds were characterized via Mossbauer and EPR spectroscopy. All Mossbauer spectra showed the characteristic doublet, proving the persistence of the ferrocene moiety. In the cases of 1, 3, and 4, appreciable impurities of ferrocenium ions could be detected by electron paramagnetic resonance spectroscopy. Cyclovoltammetric experiments were performed to demonstrate the accessible redox activity of the linker molecule of the title compounds. A redox process of FcDC(2-) with oxidation (between 0.86 and 0.97 V) and reduction wave (between 0.69 and 0.80 V) was observed.

Metal-organic frameworks containing Ga3+ ions and four differently substituted naphthalenedicarboxylates (ndc(2-)) have been synthesized and characterized. The Ga3+ ions are six-fold coordinated by oxygen atoms in all title compounds, but two different inorganic building units, i.e. trans corner-sharing and cis,trans edge-sharing octahedra are observed. Crystal structures were validated by Rietveld refinements against powder X-ray diffraction data. [Ga(OH)(1,4-ndc)]2H(2)O crystallizes in a non-breathing MIL-53 type structure with two different pore sizes (5.5 x 5.5 angstrom and 9 x 9 angstrom). It is non-porous with respect to nitrogen but has a water adsorption capacity of about 155 mg g(-1) and a thermal stability of up to 240 degrees C. The dense compound [Ga(OH)(1,8-ndc)] crystallizes in a new layered structure motif, which is related to the crystal structure of MIL-122 ([Al(OH)((O2C)(4)C6H2)]). The third and fourth compounds [Ga-2(OH)(4)(2,3-ndc)]H2O and [Ga(OH)(2,6-ndc)]H2O are isoreticular to CAU-15 ([Al-2(OH)(4)(2,3-bdc)]H2O) and MIL-69 ([Al(OH)(2,6-ndc)]H2O), respectively. The last two compounds are non-porous toward nitrogen but reversible dehydration was demonstrated. For comparison, the two new compounds [Al(OH)(1,8-ndc)] and [Al-2(OH)(4)(2,3-ndc)]H2O, which are isostructural to the newly described gallium compounds, were also synthesized and fully characterized. The Al-containing coordination polymers exhibit higher temperature stabilities compared to their isostructural Ga compounds.