Polymorphous Indium Metal–Organic Frameworks Based on a Ferrocene Linker: Redox Activity, Porosity, and Structural Diversity

Abstract

The metallocene-based linker molecule 1,1′-ferrocenedicarboxylic acid (H2FcDC) 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 1D-coordination polymer denoted as CAU-43 (1), In-MIL-53-FcDC_a (2), and In-FcDC (3) were obtained. Furthermore, thermal treatment of CAU-43 (1) at 190 °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 P1̅ 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. N2 sorption experiments of 1, 2, and 4 showed specific surface areas of 355 m2 g–1, 110 m2 g–1, and 140 m2 g–1, respectively. Furthermore, the electronic properties of the title compounds were characterized via Mössbauer and EPR spectroscopy. All Mössbauer 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 FcDC2– with oxidation (between 0.86 and 0.97 V) and reduction wave (between 0.69 and 0.80 V) was observed.

A Flexible and Porous Ferrocene‐Based Gallium MOF with MIL‐53 Architecture

“…The structural flexibility of MlL‐53 frameworks with different types of linker molecules is well known. In the case of FcDC 2− based MOFs, different aluminum and indium based compounds were reported which did not show any kind of breathing behavior or structural flexibility depending on external stimuli such as temperature or guest molecules so far [31,32] . In comparison to these isostructural compounds, Ga‐MIL‐53‐FcDC shows structural flexibility depending on which guest molecule is located in the channels of the framework.…”

“…In the case of FcDC 2À based MOFs, different aluminum and indium based compounds were reported which did not show any kind of breathing behavior or structural flexibility depending on external stimuli such as temperature or guest molecules so far. [31,32] In comparison to these isostructural compounds, Ga-MIL-53-FcDC shows structural flexibility depending on which guest molecule is located in the channels of the framework. During the solvent exchange procedure for activation, obvious changes in the peak intensity and positions can be observed, indicating structural flexibility of the MOF (Figure 6).…”

“…In the case of Al-MIL-53-FcDC no breathing behavior was observed. [31] Furthermore the employment of the linker molecule FcDC 2À in combination with In 3 + ions led to different linker conformations (synclinal and antiperiplanar) in different framework structures, [32] but no breathing could be observed either. In this contribution, we are reporting the first breathing MOF with FcDC 2À as linker molecule, denoted as Ga-MIL-53-FcDC.…”

Progress and Prospect of Organic Electrocatalysts in Lithium−Sulfur Batteries

“…The metallocene family is composed of central transition metal atoms and organic cyclopentadienyl groups (Goodwin et al, 2021). Among of them, ferrocene, which is aromatic and contains easily replaced sites, shows a high redox activity in the field of electrochemistry (Benecke et al, 2020). Using this advantage, Mi et al proposed to covalently anchor ferrocene on the graphene oxide, as shown in Figure 2A (Mi et al, 2016).…”

Co(II) coordination polymer: Treatment activity on vulvovaginal candidiasis by inhibiting the growth of the Candida albicans

“…The synthesis and the design of coordination polymers (CPs) have attracted extensive interest with their wonderful performances and architectures from a variety of molecular building blocks linked via supramolecular contacts and coordination bonds, owing to their latently extensive applications in the functional materials [4][5][6][7]. Many remarkable spectacular coordination polymers have been recorded, for instance, 1D ladders and chains, two-dimensional grids, as well as 3D helical staircase networks, interpenetrated modes, and the microporous networks [8][9][10][11]. Among the above MOFs, recently, special attention has been paid to systems with single motifs entanglements.…”