Redox-Induced Photoluminescence of Metal–Organic Coordination Polymer Gel

Abstract

In this study, we have prepared a redox-active and intrinsically nonphotoluminescent metal−organic gel comprised of iron ions and terephthalic acid. In the presence of small reactive organic molecules like pyrrole, aniline, and bithiophene, the gelation process was unaffected and at the same time it led to the formation of highly photoluminescent hybrid materials. The photoluminescence turn-on response was primarily attributed to the redox reaction between iron ions and the small organic molecules generating oxidized oligomers in the porous gel matrix. A remarkable morphological transformation of the metal−organic gel from spindle-like to nanofibers, induced by the redox reaction, was detected. The adopted synthetic approach is very simple and the ease of tailor-making photoluminescence in the materials by varying the combinations of redox system and reactive small organic molecule will open up new perspective in the field of coordination polymers, specifically, for sensors, photonics, and photovoltaic applications.

Iron–naphthalenedicarboxylic acid gels and their high efficiency in removing arsenic(v)

“…Metal-organic gels (MOGs), as a type of supramolecular gel via metal coordination interactions, [1][2][3][4][5][6][7] exhibit unique physical and chemical properties such as high conductivity and strong magnetism and possess potential applications in catalysis, 8 gas adsorption, 9 and chemical sensor. 10 It can be noted that MOGs show advantages in environmental and biological applications because of their viscoelastic and stimuli-responsive properties.…”

Synthesis of Highly Stable Porous Metal‐Iminodiacetic Acid Gels from A Novel IDA Compound

“…Benzidine, pyridine-4-carboxaldehyde, chromic nitrate nonahydrate, and aluminum nitrate nonahydrate were purchased from Sigma-Aldrich. N,N'-Bis-pyridin-4-ylmethylene-hydrazine (4-bpmb) (Scheme 1), [15,32] N,N'-(4,4'-biphenylyl) iminodiacetic acid (BP-IDA) (Scheme 2) [33][34][35] were synthesized according to the reported procedures.…”

“…The morphology and microstructure of the MIG1 and MIG2 aerogels were observed by SEM and TEM measurements (Figures 4 and S8 3＋ was evidenced by a signal at 578 eV in the Cr 2p3/2 region, and a signal at 587 eV in the Cr 2p1/2 region, [29] respectively (Figure 5a). The high-resolution spectrum shows a broad peak of N 1s, indicating the presence of C＝N at 399.5 eV [15] ( Figure 5b). IR spectra of the aerogels and BP-IDA, 4-bpmb ( Figure 6) further confirm the coordination of the carboxylate and pyridine group to metal ions, as evidenced by the shift of the C＝O stretching frequency from ca.…”

“…[9,10] Compared with MOFs, the metal-organic gels possess poor crystallinities and unclear structures, however, they still have the following advantages: (1) The reaction can proceed at a low temperature, some materials can be obtained at room temperature; (2) the reaction time is shorter and solvent quantity is less; (3) reaction solvent is cheap and with low toxicity, the reaction can proceed in ethanol, water, N,N'-dimethylformamide (DMF), or the mixture of them; (4) the easily obtained desired shapes of the gels by utilizing various shapes of reaction containers make them more suitable for industrialized and commercial applications. Due to above points, metal-organic gels have amounts of potential applications in catalysis, [11] sensing, [12] anion recognition, [13] photophysics, [14,15] vapor adsorption, [16] separation technologies, electrochemical detection, [17] etc. Conformationally flexible ligands with amide groups [18][19][20] have been often employed to design metal-organic gels because the formed networks are able to trap solvent molecules in their crystal lattices.…”

Stimuli responsive dynamic transformations in supramolecular gels

“…Ballav and co-workers undertook a similar strategy to convert a coordination polymer gel into a conducting polymer gel. 438 A metal-organic gel initially comprised of Fe(III) and terephthalic acid was subjected to redox changes in presence of organic molecules like pyrrole, aniline and bithiophene. In situ oxidation by Fe(III) led to the formation of polypyrrole, polyaniline and polythiophene, respectively, and allowed transition of the Fe(III)-gel into hybrid Fe(II)-conducting polymer gels accompanied with drastic changes in morphology and luminescent properties.…”