Construction And Application Of Porous Metal-organic Frameworks(MOFs)

Over the last at least three decades, the science of porous solid materials hasbecome one of the most intense areas of study for chemists, physicists, and materialsscientists. These materials have found a large number of applications in many felds,such as adsorption, separation and purifcation, as well as catalysis. Porous solids actingas adsorbents or membrane fllers are playing key roles in separations and purifcationsof various chemicals that we encounter in our daily activities, directly or indirectly.Explorations of advanced porous materials for these applications are therefore anintense subject of scientifc research.In this thesis, we used the simplest chemical method for the preparation of porousMOFs in the selective oxidation of cis-cyclooctene, enantioselective recognition andelectrocatalysis of chiral molecule, catalytic ability for oxygen reduction reaction (ORR)and porcine pancreatic lipase (PPL) catalyst which can be control by the size andmorphology.(1) Here we report a3D PCP, namely [Co3(μ2-OH)4(I)2]·2H2O (compound1, I=hypoxanthine), exhibiting an unprecedented3D porous framework containing two typesof1D channels running along c axis. the typical regular square (type-A and type-B)channels exhibit the sizes of11.2×11.2and8.5×8.5, respectively. In order to testifythe porous structure of1, the N2and CO2sorption isotherms were performed at77and195K on the activated samples, respectively. The activated sample1adsorbs N2andCO2of237.4and160.4cm3g1at1atm, respectively. The adsorption isotherms of N2and CO2display a steep rise at the low relative pressure region, and the isotherms canbe categorized as type I, indicating a typical physisorption process of a microporousmaterial. The catalytic experiments showed that compound1, directly used asheterogeneous catalyst without any supports, indeed possesses excellent catalytic abilityfor the selective oxidation of cis-cyclooctene (34.84%conversion based oncis-cyclooctene and87.71%selectivity for epoxycyclooctane). (2) We have demonstrated a facile chemical etching method for the fabrication ofmesoporous black TiO2nanocrystals. Here we report the synthesis of two3Dhomochiral porous coordination polymers, namely [Co2F2(bpy)2(L-tart)]7H2O (2) and[Co2F2(bpy)2(D-tart)]5.5H2O (3) from cobalt salt with4,4’-bpy, L-and/or D-tart. Both2and3exhibit a unique3D chiral porous framework containing three types of1D chiralchannels running along a, b and c axes, respectively. In order to confirm the porousstructure of2and3, theN2and CO2sorption isotherms were performed at77and195Kon the activated samples, respectively. The adsorption isotherm of CO2at195Kdisplays a steep rise at the low relative pressure region, with a small hysteresis betweensorption–desorption curves, and the isotherm can be categorized as type I, indicating atypical physisorption process of a microporous material. Further close observationreveals that the circular dichroism spectra are mirror images of one another, whichconclusively demonstrates that2and3are enantiomers. This phenomena indicated thatthe chiral information was transferred from chiral tartaric acid ligand to the metal centreand finally to the whole framework.(3) Here we report two nonporous homochiral coordination polymers, namely[Cu(H2O)(bpy)(L-DBTA)]·H2O (4) and [Cu(H2O)(bpy)(D-DBTA)]·H2O (5) assembledfrom copper salt with4,4′-bpy, L-and/or D-DBTA. Both compounds4and5exhibit3Dnonporous chiral interdigitated architectures. Further close observation reveals that thecircular dichroism spectra are mirror images of one another, which conclusivelydemonstrates that4and5are enantiomers. This phenomena indicated that the chiralinformation was transferred from chiral tartaric acid ligand to the metal centre andfinally to the whole framework.(4) The chiral porous materials (compounds2-5), possesses excellentenantioselective recognition and electrocatalytic ability towards L/D-tart and L/D-malic,respectively. The enantioselective recognition abilities of2-5were analyzed byelectrochemical impedance spectroscopy (EIS). The EIS of L-CPE in Na2SO4solutionwith L-tart showed a large semicircle in the high-frequency region, indicating aninterfacial electron transfer process on the L-CPE surface. However, the spectrum ofL-CPE for D-tart in Na2SO4solution is not observed. Similarly, in the D-CPE system,the EIS of D-CPE in Na2SO4solution with D-tart also showed a typical interfacialelectron transfer behavior on the D-CPE surface, while that for L-tart is not observed.Linear sweep voltammograms are shown for the oxidation of L-and D-tart on L-CPE and D-CPE, respectively. As shown, the L-CPE is more active for the oxidation of theL-tart, and the D-CPE is more active for the oxidation of the D-tart. In controlexperiments (using the bare CPE instead of L-and D-CPE), bare CPE shows noenantioselective recognition and electrocatalytic abilities of the enantiomers. The linearsweep voltammogram results for the different catalytic processes of L-and D-CPE werein good agreement with that of impedance experiments, which confirms theenantioselective recognition and electrocatalytic abilities of the chiral porous materials.（5）we report a facile and simple one–step approach for the synthesis of hybridcore–shell nanocomposites using compound1as precursors. The TEM image furtherconfrms the Co3O4particle with size about15nm was encapsulated into the carbonshell. The further electrochemical experiments indicated that Co3O4@N-Cnanocomposites exhibits an excellent electrocatalytic performance for a four-electronORR, and longer-term stability and higher methanol tolerance than the commercial Pt/Ccatalysts in alkaline medium.（6）Exploring porous MOFs materials performances for applications in biology isattracting intense interest of researchers working in the felds of biological chemistry.we reported an effcient method to attain highly active immobilized pig pancreatic lipase(PPL) by using the compound1as precursors. Furthermore, we demonstrated that theoptimal pH of free PPL and MOF-PPL was7.0,8.0, respectively. Free PPL activityfluctuated within a narrow pH range. The MOF-PPL system maintained high activitywas in7.0~9.0. The experimental dates revealed that the highest hydrolysis activity ofMOF-PPL was5100U g-1, whereas the activity of free PPL was3850U g-1. Meanwhile,we demonstrated that the optimal reaction temperature of free PPL and MOF-PPL was311K,318K, respectively.