| Water contamination due to the discharge of organic dyes has become a global severe issue.Nevertheless,the existing techniques comprising physical treatment by adsorption,chemical treatment by photodegradation in combination with biological method are suffering from high cost,low efficiency or secondary pollution generation et al.As an alternative material that is widely favored,MOFs can realize elimination of dyes through physical and/or selective adsorption by virtue of their intrinsic features of high porosity,host-guest interactions as well as ionicity of frameworks.As semiconductor materials,MOFs have attracted much more attentions due to the photocatalytic degradation performances towards organic dyes.However,it is still full of challenges to develop efficient and practical MOFs materials for eliminating organic dyes.Our research interests mainly focus on physical adsorption and photocatalytic degradation of organic dyes in water via MOFs combining high hydrolysis stability and photo-responsive behavior,which assembled from high valence state metal ions and highly conjugated aromatic polycarboxylic acid.Then,the photocatalytic degradation performances of MOFs were further promoted by virtue of dyes sensitization to the frameworks.The main research contents are summarized as follows.(1)Based on[In(O2C-)4]cluster,a two-fold penetrated anionic skeleton of complex 1 has been successfully obtained from In3+ and highly conjugated aromatic tricarboxylic acid.1 can remove cationic Methylene Blue(MB)dyes by selective adsorption in the present of anionic Methyl Orange(MO)molecules and demonstrates a Type I adsorption isotherm,with the adsorption rate and capacity of 1.71 × 10-3 gmg-1 min-1 and 714.3 mg g-1 respectively.The endothermic and spontaneous ion exchange adsorption characteristic has been confirmed according to the negative ?G,positive ?H and ?S in the temperature-dependent(298,308 and 318K)adsorption process.Moreover,cyclic adsorption capacity of 1 towards MB was proved by four times of consecutive desorption/adsorption cycle experiments.And the UV/visible light absorption capacities of 1 have been confirmed by UV-Vis adsorption and UV-Vis DRS spectrum,with a band gap value(Eg)of 2.89 eV.In the following photocatalytic degradation experiment,complex 1 was employed to efficiently and quickly destroy MB and MO dye molecules under UV or visible light in water,corresponding degradation efficiencies were calculated to be 95.89%and 92.80%under UV light,as well as 98.89%and 90.51%under visible light.In addition,wonderful cyclic catalytic ability and credible photostability were also identified through five times of consecutive visible light catalytic cycles.Prominently,the encouraging photocatalytic degradation performances under visible light were proved to be mainly attributed to the sensitization of MOF from introduced dye molecules.(2)In order to further find out the diversities of photocatalytic degradation performances of MOF caused by sensitizing effects of introduced dye molecules,Basic Yellow 24(BY24,?max = 420 nm),Basic Red 14(BR14,?max = 520 nm)and MB(?max ?664 nm)which are distinguished by visible light absorption wavelength ranges,were deliberately selected to offer seven kinds of composite catalysts,i.e.single dye sensitized BY24@1,BR14@1,MB@1,double dyes sensitized(MB+BY24)@1,(MB+BR14)@1,(BY24+BR14)@1 and(BY24+BR14+MB)@1 sensitized by three dyes.According to the results of UV-Vis DRS,the Eg values of MOF sensitized by single dye were calculated as MB@1(1.66 eV)<BR14@1(1.98 eV)<BY24@1(2.33 eV)<1(2.89 eV),corresponding photocatalytic degradation efficiencies towards Reactive Blue 21(RB21)were confirmed as 91.37%,88.76%,40.99%and 73.13%respectively,under visible light for 10 hours.Eg values of dual/triple dyes sensitized(MB+Yellow)@1,(MB+BR14)@1,(BY24+BR14)@1 and(BY24+BR14+MB)@1 were proved to be 1.70 eV,1.69 eV,2.08 eV and 1.72 eV,with the photocatalytic degradation performances of 93.10%@10 h,33.87%@10 h,89.98%@10 h and 95.36%@8 h towards RB21 respectively,demonstrating that the mixed dyes are superior to single dye in improving the photocatalytic degradation performances of as synthesized MOF,and the overwhelming superiority of degradation efficiency and rate were performed by(BY24+BR14+MB)@1.The only flaw is that although the PXRD of 1 is still excellent,the photodegradation efficiency of(BY24+BR14+MB)@1 towards RBlue21 decreased from 96.07%of the first cycle to 81.03%,after five times of photodegradation cycles.(3)In consideration of the absolute predominance of Zr-MOFs in water/moisture susceptibility especially have been widely studied in photochemistry,two bcu topological 3D metal-organic frameworks of2 and 3,which based on Zr6 metal clusters,2,2'-bipyridine-4,4'-dicarboxylate(H2L1)and 2,2'-biquinolyl-4,4'-dicarboxylate(H2L2)organic linkers with identical coordination pattern,have been deliberately designed.Particularly,for complex 3,which was constructed from H2L2,displayed perfect skeletal stability and crystallization even if it was exposed to atmosphere and water under ambient temperature,not to mention boiling water,concentrated acid(pH = 2)and concentrated strong base(pH = 14)of hydrochloric acid and sodium hydroxide aqueous solutions.Moreover,the thermal stability of 3 can reach up to over 500 ?,under N2 atmosphere.The neutral characteristic frameworks of 2 and 3 were confirmed through ionic selective adsorption experiments towards MB and MO.After suffering eight times of desorption-adsorption cyclic experiments in saturated NaCl methanol solution and aqueous dye solution,respectively,the adsorption efficiencies of 2(for MO)and 3(for MB)only slightly declined 3.18%and 1.44%,respectively.The 3D frameworks demonstrated extremely high electrolyte stability considering the final PXRD patterns of 2 and 3.The performances of photoabsorption and photoresponsefor complex 3(Eg = 3.26 eV)areobviously superior to2(Eg = 3.74 eV)because of the difference in conjugated degree for H2L1 and H2L2.Stubborn RB21 can be effectively destroyed through photocatalytic degradation by 2,3 and their dyes sensitized composite materials,and the photocatalytic systems from complex 3 behavedmore efficiently.It should be noticed that that the photocatalytic degradation efficiencies of MB@2 and MO@3towards RB21 only decrease by 2.73%and 1.18%,from initial 76.4%and 84.36%,respectively,even experienced eight times of recycles,indicating both high efficiency and practicability for designed Zr-MOFs.In addition,five chiral MOFs(4-8)have been successfully synthesized via chiral drug ligand voriconazole(HLVCZ)and transition metal ions,at the early stage of my investigation.Chelating,monodentate,bidentate and terdentate,a total of four kinds of coordination modes have been observed fromHLVCZ which contains muti-coordination sites,correspnding to 0D to 3D architectures for4-8,and the single chiral modes of bulk complexes 4-8 were confirmed by VCD and IR spectrum.The second-harmonic generation(SHG)intensities of complexes 4-8 were proved to be 0.3,0.4,0.6,0.8,and 0.1 times that of urea,confirming the chiral features of 4-8again.Versatility of chiral MOFs were also highlighted by the favourable ferroelectric and dielectric response properties of 4.6 and 7,especially the fairly high dielectric constant value of 1.98 x 105 for 6;at a electric field frequency 102 Hz at 350 K(the Curie temperature). |
PDF Full Text Request