Structure and Photoluminescence Tuning Features of Mn2+- and Ln3+-Activated Zn-Based Heterometal–Organic Frameworks (MOFs) with a Single 5-Methylisophthalic Acid Ligand

Recent advancement in bimetallic metal organic frameworks (M’MOFs): Synthetic challenges and applications

Metal-organic frameworks (MOFs) is a burgeoning research field and has received increasing interest in recent years due to their inherent advantages of inorganic metal ions, range of organic linkers, tunable...

A Heterometallic Three-Dimensional Metal-Organic Framework Bearing an Unprecedented One-Dimensional Branched-Chain Secondary Building Unit

A heterometallic metal−organic framework (MOF) of [Cd₆Ca₄(BTB)₆(HCOO)₂(DEF)₂(H₂O)₁₂]∙DEF∙xSol (1, H₃BTB = benzene-1,3,5-tribenzoic acid; DEF = N,N′-diethylformamide; xSol. = undefined solvates within the pore) was prepared by solvothermal reaction of Cd(NO₃)₂·4H₂O, CaO and H₃BTB in a mixed solvent of DEF/H₂O/HNO₃. The compatibility of these two divalent cations from different blocks of the periodic table results in a solid-state structure consisting of an unusual combination of a discrete V-shaped heptanuclear cluster of [Cd₂Ca]₂Ca′ and an infinite one-dimensional (1D) chain of [Cd₂CaCa′]_n that are orthogonally linked via a corner-shared Ca²⁺ ion (denoted as Ca′), giving rise to an unprecedented branched-chain secondary building unit (SBU). These SBUs propagate via tridentate BTB to yield a three-dimensional (3D) structure featuring a corner-truncated P4₁ helix in MOF 1. This outcome highlights the unique topologies possible via the combination of carefully chosen s- and d-block metal ions with polydentate ligands.

Tuning of Luminescent and Magnetic Properties via Metal Doping of Zn-BTC Systems

In order to assess how metal doping affects the luminescence and magnetic properties of anionic Metal-Organic Frameworks (MOFs), seven single-metal doped MOFs {M-Zn-BTC}{Me2NH2+} (M = Co, Cu, Ni, Mn, Ca, Mg, Cd) and three dual-metal doped MOFs {Zn-M1-M2-BTC}{Me2NH2+} (M1 = Co, Cu; M2 = Ni, Co) were synthesized. Trace amounts of different metals were doped via addition of another metal salt during the synthetic process. All compounds retained the same crystal structure as that of the parent {Zn-BTC}{Me2NH2+} MOF, which was supported by single crystal and powder X-ray diffraction studies. Thermal Gravimetric Analysis (TGA) of these compounds also revealed that all MOFs had similar stability up to ~450 °C. Solid state photoluminescent studies indicated that {Zn-Mn-BTC}{Me2NH2+}, {Zn-Cd-BTC}{Me2NH2+}, and {Zn-Ca-BTC}{Me2NH2+} had a significant red shifting effect compared to the original {Zn-BTC}{Me2NH2+} MOF. Applications of this doping method to other MOF systems can provide an efficient way to tune the luminescence of such systems, and to obtain a desired wavelength for several applications such as sensors and white light LED materials. Because Zn, Co, Cu, Ni, Mg have magnetic properties, the effect of the doping metal atom on the magnetism of the {Zn-BTC}{Me2NH2+} networks was also studied. To characterize the magnetic behavior of the synthesized MOFs, we conducted low-temperature (10 K) saturation remanence experiments in a 3 Tesla applied field, with the principal goal of identifying the domain state of the synthesized materials (Zn, Zn-Co, Zn-Cu-Co, Zn-Cu-Ni, Zn-Mg, Zn-Mn, Zn-Ni-Co, Zn-Ni). During room/low temperature saturation magnetization experiments, Zn, Zn-Co, Zn-Cu-Co, and Zn-Cu-Ni systems yielded data indicative of superparamagnetic behavior, yet during zero field and field cooled experiments Zn-Co showed a slight paramagnetic effect, Zn showed no temperature dependence on warming and Zn-Cu-Co and Zn-Cu-Ni demonstrated only a slight temperature dependence on warming. These behaviors are consistent with ferromagnetic ordering. Zero field and field cooled experiments indicate that Zn-Mg and Zn-Ni have a ferromagnetic ordering and Zn-Mn and Zn-Ni-Co show paramagnetic ordering behavior.

A 2D rhomboidal system of manganese(ii) [Mn(3-MeC6H4COO)2(H2O)2]n with spin canting: rationalization of the magnetic exchange

The crystal structure of Mn(ii) carboxylate with 3-methylbenzoate as a bridging ligand [Mn(3-MeC₆H₄COO)₂(H₂O)₂]_n shows a rhomboidal layer, where each pair of neighbor Mn(ii) ions are bridged through only one carboxylate group with a syn-anti conformation. The magnetic exchange between neighbor ions is weakly antiferromagnetic (J = -0.52 cm^-1, g = 2.04), and at low temperature the system shows spin canting with T_B = 3.8 K. Computational studies, based on periodic calculations of the energies of the significant spin states on the magnetic cell and some higher supercells, corroborate the weak AF interaction between the adjacent Mn(ii) ions and preclude the negligible effect of frustration caused by very weak interactions between the non-adjacent ions in the magnetic response of the system. The results provide compelling evidence that the observed spin canting is due to the local coordination geometry of the manganese ions leading to two antiferromagnetically coupled subnets with different axial vectors.

Mixed chelating ligands used to regulate the luminescence of Ln(iii) complexes and single-ion magnet behavior in Dy-based analogues

The organic ligands 5,7-dibromo-2-methyl-8-quinolinol (L1), 1,10-phenanthroline (L2), and 5,7-dichloro-2-methyl-8-quinolinol (L3) were used to react with Dy(NO₃)₃·6H₂O under solvothermal conditions at 80 °C to obtain the complexes [Dy(L1)₃(H₂O)] (1), [Dy(L2)₂(NO₃)₃] (2), and [Dy(L3)₃(H₂O)] (3), respectively.

A Europium ion post-functionalized indium metal–organic framework hybrid system for fluorescence detection of aromatics

A Eu³⁺-functionalized indium metal–organic framework hybrid system is employed as a fluorescent probe for the discrimination of BTEX in both the liquid and the gas phase.

Two bilayer metal–organic frameworks with rare trinuclear heterometal clusters and tunable photoluminescence

Two bilayer metal–organic frameworks based on rare trinuclear Pb/K and Cd/Na clusters have been solvothermally synthesized. They exhibit tunable purple-to-red-to-green and purple-to-green photoluminescence by variation of excitation light, respectively.

A series of Mg–Zn heterometallic coordination polymers: synthesis, characterization, and fluorescence sensing for Fe3+, CS2, and nitroaromatic compounds

Herein, three luminescent Mg–Zn coordination polymers were constructed, which demonstrated high fluorescence sensing of Fe³⁺, CS₂, and nitro explosive compounds.

Coordination polymers of 5-substituted isophthalic acid

The synthesis and characterisation of five coordination polymers - Ni2(mip)2(H2O)8·2H2O (1), Zn6(mip)5(OH)2(H2O)4·7.4H2O (2), Zn6(mip)5(OH)2(H2O)2·4H2O (3), Mn(HMeOip)2 (4), and Mn3(tbip)2(Htbip)2(EtOH)2 (5) - are reported. Preliminary nitric oxide release data on compounds 2 and 3 are also given.

Layer-structured coordination polymers based on 5-(1H-tetrazol-5-yl)isophthalic acid: structure, sensitization of lanthanide(iii) cations and small-molecule sensing

Compound 1 can serve as a host for encapsulation of Ln³⁺ ions.

Coordination polymers of ZnIIand 5-methoxy isophthalate

Four different coordination polymers were prepared by reaction of Zn(OAc)₂and 5-methoxy isophthalic acid using various aqueous/aqueous alcohol solvent systems.

Two dimensional porous 3d–4f heterometallic coordination polymers constructed by pyridine-2,3-dicarboxylic acid

Four porous Co^IIILn^III 3d–4f heterometallic coordination polymers constructed by the pydcH₂ ligand were hydrothermally synthesized and characterized. The adsorption and catalytic properties of compound Co^IIIDy^III were investigated.

In situ solvent and counteranion-induced synthesis, structural characterization and photoluminescence properties of Pb-based MOFs

With solvents or counteranions as the only variable, three novel photoluminescent Pb-based metal–organic frameworks were obtained under the similar synthetic procedures.

Luminescent metal–organic frameworks for chemical sensing and explosive detection

This review provides an update on the photoluminescence properties of LMOFs and their utility in chemical sensing and explosive detection.

Rational design and synthesis of a series of 3D lanthanide metal–organic frameworks with different structures driven by reaction conditions

A series of novel lanthanide metal–organic frameworks with three types of structures, moc, dia and a new topology, have been constructed and their luminescence properties were investigated.

Luminescence tuning and white-light emission of co-doped Ln-Cd-organic frameworks

Four new three-dimensional isostructural lanthanide-cadmium metal-organic frameworks (Ln-Cd MOFs), [LnCd(2)(imdc)(2)(Ac)(H(2)O)(2) ]·H(2)O (Ln=Pr (1), Eu (2), Gd (3), and Tb (4); H(3)imdc=4,5-imidazoledicarboxylic acid; Ac=acetate), have been synthesized under hydrothermal conditions and characterized by IR, elemental analyses, inductively coupled plasma (ICP) analysis, and X-ray diffraction. Single-crystal X-ray diffraction shows that two Ln(III) ions are surrounded by four Cd(II) ions to form a heteronuclear building block. The blocks are further linked to form 3D Ln-Cd MOFs by the bridging imdc(3-) ligand. Furthermore, the left- and right-handed helices array alternatively in the lattice. Eu-Cd and Tb-Cd MOFs can emit characteristic red light with the Eu(III) ion and green light with the Tb(III) ion, respectively, while both Gd-Cd and Pr-Cd MOFs generate blue emission when they are excited. Different concentrations of Eu(3+) and Tb(3+) ions were co-doped into Gd-Cd/Pr-Cd MOFs, and tunable luminescence from yellow to white was achieved. White-light emission was obtained successfully by adjusting the excitation wavelength or the co-doping ratio of the co-doped Gd-Cd and Pr-Cd MOFs. These results show that the relative emission intensity of white light for Gd-Cd:Eu(3+),Tb(3+) MOFs is stronger than that of Pr-Cd:Eu(3+),Tb(3+) MOFs, which implies that the Gd complex is a better matrix than the Pr complex to obtain white-light emission materials.