Design, Synthesis And Properties Of Functional Metal-organic Frameworks

Metal-organic frameworks (MOFs), as a novel kind of materials, are usuallyconstructed by organic connection structure units and inorganic metal structure units.This thesis mainly introduces two types of MOFs with different properties. Oneconsists of a binuclear paddlewheel-type [Cu2(COO)4] cluster, which is connected bytetracarboxylate ligand DBIP4to construct a compound with excellent carbon dioxideadsorption property. Another is related to white light emission and temperaturesensing properties and is built by europium ion, terbium ion and carboxy acidcontaining alkynyl. In addition, we also prepared an organic fluorescent probe forrecognition of heavy metal ions and anions in aqueous solution, or even in biologicalcells. The result indicates that this fluorescent molecule is non-toxic to organisms andsensitive for ion detection, which suggests its potential application values inenvironment or biology. Specifically, this thesis can be mainly divided into thefollowing three parts:1. The study of metal-organic frameworks constructed by5-(3,5-dicarboxybenzyloxy)isophthalic acid (H4DBIP) and binuclear copper clusterswith excellent carbon dioxide adsorption property. Single-crystal X-ray diffractionanalysis reveals that this compound crystallizes in the monoclinic space group P21/c.In compound, the copper ions exist as a binuclear paddlewheel-type [Cu2(COO)4]cluster to form a4-connected square-planar node, which is linked by the4-connectedtetracarboxylate ligand DBIP4, resulting in a three-dimensional(3D),4,4’-connectednbo-type framework. There are two types of metal ligand cages in the structure ofthis compound. The smaller spherical cage consists of six [Cu2(COO)4] clusters andsix DBIP4ligands, and the diameter is about9.3. The larger ellipsoidal cage is constructed of12[Cu2(COO)4] clusters and6DBIP4ligands with dimensions of ca.12.4×17.7. These two cages are arranged alternatively to form a cage-stacked3Dframework with nbo topology. Then, we explor the permanent porosity of theframeworks using low-pressure N2adsorption measurements at77K, which showsthe BET surface area is1773m2/g. Moreover, the CO2adsorption isotherm exhibitsan exceptionally high CO2uptake of170cm3/g (7.59mmol/g) as well as goodselectivity of CO2/N2(20.6) under0.95bar at273K. In addition, this compound couldbe utilized as a reusable sorbent for CO2capture and could be easily regeneratedthrough heating.2. The research about Eu3+-doped Tb3+metal-organic frameworks with whitelight emission and temperature sensing properties. We have designed and synthesizeda series of europium ion doped terbium ion metal-organic frameworks, which arenamed1,2,3,4,5,6,7,8, respectively. Through adjusting the two metal ions mixproportion in raw material, we realize the fluorescence color changes from blue to redunder UV irradiation. When the concentration ratio of Eu3+/Tb3+is0.5%:99.5%, thecompound4(Tb0.995Eu0.005CPEIP) emits white-light and coordinates value is (0.34,0.31) on the CIE chromaticity diagram calculated by the emission data, which is closeto the white light ideal value (0.33,0.33). Then, we studied the temperature sensingproperties of compound4. The results show that when the temperature increases from80K to330K, fluorescent color changes from orange to red. In low temperature area,we find that ITb/IEuand temperature T accords with the following linear relationship,T=175.0-159.1ITb/IEuwith the scope of the80K to175K. Thus, this kind of compounds can be used asfluorescence ratio meter in low temperature range.3. An “on-off-on” fluorescent sensor for the sequential selective detection ofCu2+, Pb2+and PPi in aqueous media and in living cells. A novel fluorescent sensor9,10-bis-(3,5-dicarboxyl-phenylethynyl)anthracene (4s) with both an anthracenemoiety and a carboxyl moiety has been designed and synthesized as a sequential selective detector of Cu2+, Pb2+and pyrophosphate (PPi) anion, which has the largestemission peak at475nm under the330nm ultraviolet excitation. In aqueous media,the presence of Cu2+and Pb2+can lead to a distinct fluorescence quenching called“turn off” sensing properties compared with other cations, respectively. Moreover, theresulting Cu2+-complex exhibits excellent “turn on” sensing properties for detection ofpyrophosphate (PPi) anion, and adenosine triphosphate(ATP) can also be detected inaqueous solution by this4s-Cu2+complex. These sensors possess high selectivityavoiding the interference from other ions (cations and anions) and the high detectionlimit. Above all, the simple sensor can serve as an “on-off-on” fluorescent detectionplatform for the sequential selective recognition of Cu2+, Pb2+and PPi in aqueousmedia. Moreover, Pb2+can be effectively detected in living cells and the addition ofEDTA makes this process be completely reversible.This thesis mainly focuses on metal-organic frameworks with gas adsorption andfluorescence emission properties. Based on the principle of crystal engineering, wefinally obtained metal-organic frameworks with specific structures and excellentproperties by selecting suitable metal ions and organic ligands. In addition, we alsodiscussed the application of fluorescent probe molecule on the ions detection inaqueous solution and orgnisms. It fully confirms that the structure determins theproperties, which provides some new ideas in the design and synthesis of organicligands of porous materials.