The Effect On Properties Of Metallamacrocycle-based MOFs Induced By Structure Tuning

Coordination polymers or metal organic frameworks (MOFs) have been one ofthe most interesting research field in the last two decades, mainly due, on one hand,to the fact that their aesthetically pleasing structures and, on the other hand, to theirpromising potential applications in heterogeneous catalysis, magnetism, gas storageand photochemistry. The main challenge in this field is to design novel building unitand explore advanced crystalline metal-organic materials with more superiorproperties, and theen to determine the influence on the properties of MOFs andunderstand relationship between structure and properties. In this paper, with the aimof preparing novel metal-organic materials with intriguing structures and goodproperties, we select5’-(pyridin-2-yl)-2H,4’H-3,3’-bi(1,2,4-triazole)(H2pbt), anasymmetric triazolate derivative, as a ligand, and obtain12newmetallamacrocycle-based or cages-based metal-organic frameworks with specialproperties under the specific transition metal ions and auxiliary reagents.This work includes the following four parts:1) Combine with H2pbt and CuSO4·5H2O, three dodecamericmetallamacrocycle-based3D frameworks have been synthesized. The magneticmeasurement results reveal that there are strong antiferromagnetic couplingsbetween the dual-copper ions bridged by doubly N1,N2-triazoles, and the higer thesymmetry of the bridged dinuclear, the stronger the antiferromagnetic couplingbetween the dinuclear. The catalytic property measurement results of these MOFs inthe oxidative coupling reaction show that the catalytic activity of the MOFs is notonly associated with the cavity size of MOFs, but have a great relationship with thestability of the MOFs.2) Three Fe-based MOFs have been synthesized by the reactions of H2pbt withFeSO4·7H2O in the presence of KSCN under solvothermal conditions. Interestingly,crystals of3-1allows to stand at160°C for one day undergoing an irreversible lostof one free water molecules to yield {[Fe2(pbt)2(H2O)2]·H2O}n(3-2) accompaniedby a color change from yellow to deep red. Moreover, the dehydration triggers the noticeable changes in catalytic and magnetic properties. These property changes areattributed to the high spin to low spin transition of7.1%center Fe(II), which isdemonstrated by57Fe M ssbauer spectra, XPS, and UV/Vis absorption spectra.3) Reaction of H2pbt with CoCl2·6H2O or Mn(OAC)2·4H2O generates threeoctanuclear metallamacrocycle-based3D MOFs. The magnetic measurement resultsreveal that there are weak antiferromagnetic couplings between the dual-cobalt ordual-manganese ions bridged by double N1,N2-triazoles.4) Under hydrothermal conditions, the ligand H2pbt with CuSO4·5H2O in thepresence of kCl and5-amino-isophthalic acid give rise to two Cu(I)/Cu(II)-based3D metal-organic frameworks. The catalytic property measurement results show thatalthough with identical frame structures these two Cu(I)/Cu(II)-based MOFs exhibitdifferent catalytic activity because the different counterions in the cages.