Synthesis And Properties Of Optoelectronic Metal-Organic Frameworks

Metal-organic frameworks(MOFs)are an exciting class of porous crystalline materials that are orderly constructed from multi-dentate organic linkers and discrete metal ions or clusters.Since their reports in the 1990s,the whole society of chemistry has witnessed the fast development of MOFs.Compared with the traditional inorganic porous materials,the organic linker and metal node of MOFs could be facilely adjusted,thus design of MOF materilas with desired properties or improved performance could be realized.Using organic ligands or metal nodes with photoelectric properties to fabricate MOFs would render the resulting materials unique photoelectric properties.Among the vast family of MOF materials,photoelectric MOFs,which develop fast nowadays,has attracted a surge of research interest.Different from the commonly used carboxylate ligands in MOFs,porphyrin was a class of conjugated macrocycle molecules with unique optoelectronic properties.Using porphyrin molecules as ligands to construct porous crystalline materials via coordination bonds give rise to metal-porphyrinic frameworks(MPFs),which belong to a new branch of MOFs.Thanks to the photoelectricity nature of porphyrins,MPFs exhibit fascinating properties that made them as eligible candidates for artificial light-harvesting,fluorescent sensing,(photochemical)catalysis,photodynamic therapy,etc.This thesis mainly aimed to construct novel MPFs with high chemical and thermal stabilities and explore their applications in(photochemical)catalysis.Meanwhile we also make effort to develop new methods to modify the structure of existing stable MOFs to improve their performance in photocatalysis.Briefly,this thesis was divided into the following chaptersChapter 1,introduction.A brief introduction to MOFs,zirconium based MOFs(Zr-MOFs)and MPFs was present.We summarized recent dvelopments of Zr-MOFs and MPFs,including their syntheis,structural features and potential applications.Chapter 2,Tuning the Properties of Metal-Organic Framework UiO-67-bpy via Post-Synthetic N-quaternization of Pyridine Sites.A new UiO-67-type zirconium MOF material UiO-67-bpy-Me(bpy=2,2-bipyridine-4,4’-dicarboxylic acid,Me=methyl)was prepared by N-quaternization of the pyridine sites in UiO-67-bpy.After N-quaternization,the pristine neutral framework turned to being cationic while its high thermal and chemical stabilities were primarily reserved.Fast and enhanced anionic dye adsorption was observed in UiO-67-bpy-Me.In addition,despite the decrease in surface area and pore volume,UiO-67-bpy-Me exhibited an evident increase in CO2 uptake compared to UiO-67-bpy.More importantly,as the N-quaternization has changed the electronic structure of the organic linker,UiO-67-bpy-Me showed optical absorption up to ca.800 um with a large red shift of 450 nm compared to the pristine UiO-67-bpy(ca.350 nm).The extended optical absorption may lead to more efficient in light utilization.A proof-of-concept demonstration showed that UiO-67-bpy-Me could more efficiently catalyze MO degradation under UV-Vis light irradiation than the pristine UiO-67-bpy.Chapter 3,Stable Metal-Porphyrin Frameworks based on Rare Earth Clusters and Meso-(4-carboxyphenyl)porphyrin.A series of microporous rare earth(RE)based MPFs,namely NUPF-1M,where M represents Y,Gd,Yb,Er,Tb,Dy,have been synthesized.The RE ions in NUPF-1M formed a rarely seen 12-connected RE9 cluster.To the best of our knowledge,NUPF-1M represents the first example of such highly-connected RE cluster based MPFs.NUPF-1M possessed a rarely seen shp-a topology.By the merit of high connection of RE9 cluster,NUPF-1M exhibited high chemical and thermal stabilities as well as permanent porousity.NUPF-1M preserved its crystalline structure in pH=2～12 solutions and under 400 0C heating After post-metalized with FeCl3,NUPF-1-FeCl could be served as an excellent heterogeneous catalyst for N-H carbene insertion with high yield and good recyclability.Chapter 4,Metal-Porphyrinic Frameworks based on Amido-decorated Porphyrin Ligand.A new porphyrin ligand with amido-decorated arms and two MPFs based this ligand have been synthesized.NUPF-2,which was constructed from In3+ and the newly prepared porphyrin ligand,possessesed a rare 4-fold interpenetrated PtS-type topology with large solvent accessible voids.The structure of NUPF-2 could be preserved in solution with pH ranging 1 to 12 for 2 days,exhibiting a high chemical stability.NUPF-2 exhibited a selective CO2 adsorption over N2.Further experiments demonstrated that NUPF-2 could be used as an excellent heterogeneous catalyst in catalyzing CO2 chemical fixation under mild conditions.Mesoporous NUPF-3 was constructed from 8-connected Zr6O8 cluster and porphyrin linker,possessing an unprecedented doubly-interpenetrating scu net.The structure exhibits not only remarkable chemical and thermal stabilities,but also a distinct structural flexibility,which is rarely seen in MOF materials.By the merit of high chemical stability,NUPF-3 could be easily post-metallized with Ru3(CO)12,the resulting NUPF-3-RuCO is catalytically active as a heterogeneous catalyst for intermolecular C(sp3)-H amination.Excellent yields and good recyclability for amination of small substrates with various organic azides have been achieved.Meanwhile,a facile method of fabricating Pt nanoparticles into NUPF-3 networks by in-situ protonation of the porphyrin ring was also described.The prepared Pt@NUPF-3 proved to be an effective catalyst in the reaction of aerobic photocatalytic oxidation of amines to imines under visible light and air atmosphere.To the best of our knowledge,Pt@NUPF-1 represents the first example of MOFs meterials that could be effectively catalyzing photocatalytic oxidation of amines to imines under air conditions.Chapter 5,A Metal-Porphyrinic Framework Based on a Novel Porphyrin Ligand Bearing Phenylpyridine Arms.An unprecedented poiphyrin ligand bearing phenylpyridine side-chains has been successfully synthesized.By using this liagnd,a novel MPFs namely NUPF-4 has been fabricated.The crystal structure of NUPF-4,which has been solved by using synchrotron X-ray diffraction,was composed of 8-connected Zr6O8 clusters and the newly synthesized porphyrin ligand,and possessed a rarely seen sqc topology.Large two-dimensional channels of 31.3 X 13.7 A and 18.8 X 13.2 A were observed in NUPF-4,which made NUPF-4 highly opened with 82.2%solvent accessible voids.Notably,the resistance of acid of NUPF-4 was remarkable among the reported MOF materials.The structure of NUPF-4 could be preserved in concentrated HCl for two weeks.Further experiments demonstrated that the porphyrin core and phenylpyridine moieties of NUPF-4 could be easily post-metalized with FeCl and Ir-complex,which made NUPF-4 as a fascinating platform for various applications.Chapter 6,Conclusions and Outlook.The results of this thesis were summarized and outlooks for our future work were also given.