MOFs Of BTB Ligand:Syntheses,Characterizations,and Property Investigations

Metal-organic frameworks(MOFs)as a new type of inorganic-organic hybrid porous materials are widely used in diverse fields,such as in gas storage,separation,optical materials,catalysis,biosensing,and drug delivery.This originates from their simple synthesis,rich structural patterns,large surface areas,adjustable porosity,facile surface functionalization,biocompatibility,and so on.Rigid carboxylate ligands are dominantly used for MOF preparation and subsequent property investigations due to their stable skeleton and versatile coordination modes of carboxylate.In this thesis,we studied the dynamic reaction process,structure and properties of MOFs constructed from benzene-1,3,5-tribenzoicacid(H3BTB).The main work is summarized as follows:In the introductory chapter,we reviewed the progress of MOFs based on the BTB ligand.In the second chapter,we systematically studied the dynamic tandem single-crystal to single-crystal(SCSC)conversion cycle of a two-dimensional(2D)MOF[Cd3(BTB)2(DEF)4]·2(DEF)0.5(1;DEF=N,N'-diethylformamide)based on linear cluster secondary building units(SBUs),following our previous reports on the SCSC of MOF 1 via ligand exchange.Crystals of MOF 1 immersed in a CHCl3 solution of trans-1,2-bis(4-pyridyl)ethylene(BPEE)yields an interpenetrated three-dimensional(3D)MOF of[Cd3(BTB)2(BPEE)(H2O)2]·(BPEE)·xSol(2;Sol=encapsulated solvates),which,in turn,undergoes a cascade conversion when immersed in DEF,yielding[Cd3(BTB)2(BPEE)1.8(DEF)0.9(H2O)0.8]·xSol(3a)over 100 seconds and[Cd3(BTB)2(BPEE)2(DEF)2]·xSol(4)after one hour,before finally shuttling back to MOF 1 after six hours.This cycle of solid-state conversions was monitored at the molecular level by X-ray crystallography and on a macroscopic scale by atomic force microscopy(AFM).These results are a cautionary tale of the surprising behavior of donor solvents that are otherwise considered to be benign facilitators in MOF conversions.In chapter three,we reported a 3D MOF of[Cd6Ca4(BTB)6(HCOO)2(DEF)(H2O)12]·DEF·xSol(7)when a mixed metal source of Cd2+and Ca2+are used during the preparation of MOF 1.MOF 7 features a completely different,and much more complicated structure as compared to that of MOF 1.It is constructed from the association of a novel one-dimensional(1D)SBU and BTB ligand,which,in turn,consists a linear 1D infinite[Cd2CaCa']n chain and a V-shaped heptanuclear[Cd2Ca]2Ca'cluster via sharing a Ca2+ ion(denoted as Ca'),and these SBUs propagate via tridentate BTB to give a complicated 3D structure featuring a corner-truncated P41 helix.We report its preparation strategy,crystal structure and properties in detail,and believe that a careful selection of s-block metals to mix with transition metal ions can be a powerful strategy for preparing MOFs with interesting topologies and unique functions.In the fourth chapter,nanoscale 2D layered MOFs of Zr4+or Hf4+ with a large number of defect sites,namely,[M6O4(OH)4(HCO2)6(BTB)2](M=Zr,Hf),have been synthesized with formic acid as the modulator.Upon activation,these nano-sheets can react with cisplatin pro-drug to obtain the ideal drug-anchored materials,which exhibits the potential to be further applied to cancer treatment at the cellular level and in vivo.