Metal–Organic Nanoporous Structures with Anisotropic Photoluminescence and Magnetic Properties and Their Use as Sensors

Abstract

The field of multifunctional materials has seen very rapid progress since the discovery of structures with a variety of technologically useful properties such as nanoporosity, [1][2][3] luminescence, and magnetism for sensors, [4][5][6] lasers, [7,8] nonlinear optics, [9] displays, [10] and electroluminescent devices.[11]After these discoveries, one of the most appealing aims is to explore multifunctionality, especially in designed materials, which combine in the same crystal a set of well-defined properties for specific applications. Lanthanide-based porous metal-organic frameworks (Ln-MOFs) [12][13][14][15][16][17] are excellent candidates to create multifunctional materials for sensors, provided that their photoluminescence and emission lifetimes are not influenced at ambient conditions by the presence of water. [5,[18][19][20] Existing Ln-MOF materials are thermally stable in air only up to approximately 673 K, [5,18,21] while pore diameters are too small to allow the diffusion of molecules of interest. [21,22] These properties preclude their use in luminescence sensors working in the presence of moisture at ambient temperature.MOFs that combine magnetic and anisotropic properties with high emission quantum yields under ambient conditions will open new possibilities for low-cost sensors.[23] Herein, we have synthesized, by rational design, novel crystalline MOFs containing rare-earth ions that combine hydrophobicity, high adsorption capacity, high thermal resistance, anisotropic photoluminescence, and magnetic properties. These materials preserve their photoluminescence properties in the presence of water and show excellent sensor capabilities.For achieving the above properties, we have chosen an organic spacer that fulfils the following requirements: high hydrophobicity, antenna effect, strong interaction with the metal center, and at least two coordination centers in order to obtain microporous 3D structures. High hydrophobicity was attained with ultrahydrophobic ligands, such as multiaromatic and C(sp 3 ) fluorinated spacers. The antenna effect can be present in a spacer with aromatic or multiaromatic groups. Moreover, rare-earth ions have high affinity for oxygencontaining molecules, for example those with carboxy groups, which produce robust framework architectures.[24] One spacer that fulfills the above requirements and that can be adequate to synthesize MOFs [25][26][27] is 4,4'-(hexafluoroisopropylidene)-bis(benzoic acid) (HFIPBB).Herein, under appropriate synthesis conditions and in the presence of HFIPBB, new Ln 3+ -based materials ITQMOF-1 and ITQMOF-2 (ITQMOF = Instituto de Tecnologia Quimica Metal Organic Framework), with similar properties but different crystallographic structures, have been obtained. To obtain the desired properties (luminescence and magnetism), different samples have been prepared with all the Ln elements except for the radioactive promethium. For mixed Ln 3+ samples, their molar composition (%) is given in parenthesis.The ITQMOF-1 material was obtained by reacting the HFIPBB...

Nanoporous polymeric materials: A new class of materials with enhanced properties

“…), the current trend in designed materials implies the achievement of a material that combines a set of well-defined and enhanced properties. For instance, Harbuzaru and coworkers [235] proposed lanthanide-based nanoporous metal-organic frameworks (Ln-MOFs) as a material with interesting multifunctional properties such as luminescence, magnetism, hydrophobicity, and high thermal stability (no specific data are provided for the cellular structure or for the properties mentioned). However, nanoporous silica aerogels films (thicknesses between 3 and 110 nm) with porosities higher than 75% (pore size not specified) have also been proposed by Hrubesh and Poco [236] as multifunctional materials because of the excellent optical, acoustical, thermal, and electronic properties exhibited by this system and demonstrated elsewhere [237,238].…”

Crystal structure of poly[diaqua-(1,10-phenanthroline-κ2 N,N′)-(μ2-2,5-dihydroxytere-phthalato)-bis(μ4-2,5-dihydroxyterephthalato)dicerium(III)], C24H16CeN2O10

“…In the synthesis of coordination polymers, nitrogen-containing organic ligands are commonly used. The 2 ]n. Each Ce(III) ion is eightcoordinated by two nitrogen atoms (N1, N2) from one chelating ligand phen, ve oxygen atoms (O1, O2, O5, O6, O7) from ve carboxylic acids of ligands dhta (cf. the gure) and one oxygen atom from a coordinated water molecule.…”

“…Coordination polymers possess both the rigid structure of inorganic compounds and the functionality of organic compounds, which bring them potential applications in the elds of magnetics, non-linear optics, catalysis, chiral recognition and separation etc. [1][2][3]. So, the design and synthesis of functional coordination polymers have attracted much attentions [4,5].…”

A Metal-Organic Framework Constructed of 1,2-Di(pyridin-4-yl)ethyne, Terephthalic Acid, and Zinc(II) Nitrate

“…The combination of metal ions with polytopic organic linkers allows for a fascinating diversity of structures which have been the subject of extensive exploration during the last decade. Potential applications of microporous (pores less than 20Å), mesoporous (pores between 20 -500Å), and macroporous metal-organic frameworks (openings > 500Å) in hydrogen [4,5] and methane [6] gas storage, selective gas absorption [7,8], sensing [9] and drug storage [10] have been reviewed recently [11 -13]. A great deal of attention has also been directed toward catalytic properties of metal-organic frameworks [14,15], among those catalytic Mukaiyama aldol reactions [16], transesterifications [17], and the chiral secondary alcohol synthesis by addition of diethyl zinc to aromatic aldehydes in the presence of a chiral MOF [18].…”