Removal of organic pollutants by lanthanide-doped MIL-53(Fe) metal-organic frameworks:Effect of dopant type in magnetite precursor

A series of undoped and lanthanide doped MIL-53(Fe)/Ln-Fe_(3)O_(4)(Ln=La,Nd,or Gd) metal-organic frameworks(MOFs) were prepared by the solvothermal method.All prepared samples were characterized by X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),Brunauer-Emmett-Teller(BET) measurements,scanning electron microscopy(SEM),and thermal analysis.XRD and FT-IR results ascertain the successful MOF formation for all prepared samples.MIL-53(Fe)/La-Fe_(3)O_(4) has the smallest particle size of 8.6 nm,the largest BET surface area of 54.2 m^(2)/g,and the highest porosity.Undoped and different lanthanide doped MIL-53(Fe) we re employed as sorbents for the removal of methylene blue(MB)dye from aqueous solutions to examine the doping benefit and the effect of the dopant size on the sorption performance.Doping causes MOFs to act as pH-independent sorbents,which make it applicable at any condition.Adsorption follows pseudo-second-order kinetic model,and doped sorbents attain equilibrium faster.Langmuir isotherms are followed,except for MIL-53(Fe)/La-Fe_(3)O_(4).The adsorption capacity increases with increasing the dopant ion size,100.5 mg/g for La-doped MOF,which is about four times higher than that of undoped MOF.The adsorption mechanism involves chemical interactions between Lewis acid in magnetite MIL-53(Fe) series and Lewis base in MB.

Functionalized Metal-organic Frameworks for White Light Emission and Highly Sensitive Sensing of PA and Fe^(3+)/Al^(3+)

Three isomorphic Ln-MOFs[Ln(bcbob)(H_(2)O)(DMF)](Ln=Tb for 1,Eu for 2,Gd for 3;DMF=N,N-dimethylformamide)have been constructed from a semi-rigid V-shaped organic linker 3,5-bis((4'-carboxyl-benzyl)oxy)benzoilate acid(H3bcbob)under solvothermal conditions.X-ray single-crystal diffraction analysis re-veals that they exhibit a two-dimensional(2D)layered structure.Compounds 1~3 show the characteristic green and red emissions of Ln^(3+)and blue emission arising from the organic ligand,respectively.Based on their photo-luminescence properties,the white-light emitting materials 4 and 5 with longer fluorescence lifetime(ms grade)and higher quantum yield(e.g.40.61%for 4)are fabricated.Remarkably,1 exhibits good sensing ability on ni-troaromatic compounds,especially for picric acid(PA).In addition,1 is still a highly selective sensing material for Fe^(3+)and Al^(3+).

Studies of two lanthanide coordination polymers built up from dinuclear units

The two three-dimensional oxo-bfidged lanthanides {[Ln2（C4H2O4）3（H20）4]· 3H2O}3, with Ln=Ho3＋ （1）; Gd3＋ （2）, are isomorphous. They have layer-type structures built up from non-centrosymrnetric dinuclear unit Ln2O12（H2O）4, beside three lattice H20 molecules stabilizing the 3D open-frmnework. The building entities are linked through one classical syn-anti g2-carboxylato-K1O：K^1O＇ bridge. Within the bi-polyhedra, two double μ2-O＇; K2O,O＇ bridges and a syn-syn classical one, support the magnetic measurements carried out on holmium compound indicating relatively weak anti-ferromagnetic interactions. The compari- son with magnetic studies on the almost similar reported Gd（III） compound, suggested that concomitant antiferromagnetic and ferro- magnetic properties could not be excluded. The two distinct thermal behaviors evidenced the higher metal-water bond strength with the smaller cation, and revealed the great supramolecular effects generated by hydrogen-bonding patterns.