Microporous Functional Materials Constructed By Bipyridine-Dicarboxylate Bridging D-f Metals

Microporous metal-organic frameworks (MOFs) present promising applications in adsorption, catalysis, luminescence, magnets due to their devisable structures. In this dissertation, thirty-eight3d-4f MOFs based on2,2’-dipyridine-4,4’-dicarboxylate (H2BPDC) as ligand have been synthesized and characterized. Structure modulation and properties covering luminescent probe for pollutant anions, slow magnetic relaxation, magnetocaloric effect, adsorption of iodine and modulation of polyiodide are thoroughly studied. Details are as following:1. Neutral and cationic MOFs were obtained based on mononuclear Ln(Ⅲ), binuclear paddle-wheel [Ln2], tetranuclear cubane [Ln4], pentanuclear trigonal bipyramidal [Ln5] as nodes respectively.1-7are two-fold interpenetrating neutral MOFs based on mononuclear Ln(Ⅲ).8-14are neutral non-interpenetrating MOFs based on [Ln2].15-38are all cationic MOFs. Noteworthily, trigonal bipyramidal [Ln5] is rather rare and only one example has been reported up to now.2. Luminescent properties were well investigated based on MOFs containing Eu(Ⅲ)、Tb(Ⅲ)、Dy(Ⅲ). The results indicate1and3can probe for nitrobenze. It may be ascribed to the nitrobenze, which absorbs the energy of the excited light.15and16can high-sensitively probe for Br-and Ⅰ-. The lowest detection limit of Ⅰ-reaches to0.001ppm based on16. Also,16can selectively, quantitatively, reversibly probe for Br-and Ⅰ-in given conditions. The unique luminescence response mechanisms were well investigated by single-crystal diffraction, UV, Raman, XPS measurements. Single-crystal structure and UV analyses reveal that Br-and Ⅰ-enter into the channels by anion exchange. Interestingly, Ⅰ-in the channels are quickly oxidized into Ⅰ2, which further combine Ⅰ-to form into Ⅰ3-. Ⅰ3-may absorb the energy of the excited light and weaken the energy transfer from the ligand to Ln(Ⅲ), resulting in the luminescence decrease. The heavy atom effect of Br-and H-bonding among Br-and coordinated water molecules lead to the luminescence enhancement. It is the first report that MOF-based luminescent probe to detect Ⅰ-and Br-, as well as the first observation of fast conversion from I-to Ⅰ3-under the existence of MOFs.20exhibits fast, selective capture and luminescent probe of pollutant CrO42-by anion exchange. Similarly, anions in the channels of24,26and27can also be exchanged by some common anions. The dynamic of exchange was studied. Anions exchanges lead to different effect on the luminescence of24,26and27. Interestingly, ⅠO3-enters into the channel and replaces one coordinated water molecule, causing the luminescence enhancement. Ⅰ-enters into the channel and also be oxidized into Ⅰ2, which quenches the luminescence.3. Magnetic properties were conducted on the MOFs containing Gd(Ⅲ), Dy(Ⅲ), Ho(Ⅲ) and Tm(Ⅲ). Among them,6,17,18and20display single molecule magnetic behavior. For6and17, it is the first time that the anions-induced the changes of both structure interpenetration and the magnetic property in3d-4f MOFs. Magnetocaloric effects of Gd(Ⅲ)-based MOFs were well studied. The magnetic entropy (-ΔSm) changes from19.40(2) to46.00(22) J kg-1K-1.4. Adsorption of iodine and modulation of polyiodide were explored based on29. The adsorption of iodine is16.25mg/g. In various solvents with iodine, Ⅰ-、Ⅰ2、Ⅰ3-、 Ⅰ82-、Ⅰ9-were observed by single crystal diffraction analysis. Presumably,29plays an important role in the formation of polyiodide. Ⅰ82-、Ⅰ9-are discovered based on MOF as "container" for the first time.