Tetrakis 4-pyridyloxymethylene Methane Research Articles

Effect of Unsaturated Metal Site Modulation in Highly Stable Microporous Materials on CO2 Capture and Fixation.

We have designed and synthesized two unprecedented microporous three-dimensional metal-organic frameworks, {[Cd6(TPOM)3(L)6]·12DMF·3H2O}n (1) and {[Zn2(TPOM)(L)2]·2DMF·H2O}n (2), based on a flexible quadritopic ligand, tetrakis(4-pyridyloxymethylene)methane (TPOM), and a bent dicarboxylic acid, 4,4'-(dimethylsilanediyl)bis-benzoic acid (H2L). The networks of 1 and 2 share a 4-c uninodal net NbO topology but exhibit different metal environments due to coordination preferences of Cd(II) and Zn(II). The Cd(II) center in 1 is six-coordinated, whereas the Zn(II) center in 2 is only four-coordinated, making the latter an unsaturated metal center. Such modulation of coordination atmosphere of metal centers in MOFs with the same topology is possible due to diverse binding of the carboxylate groups of L2-. Both 1 and 2 have relatively high thermal stability and exhibit permanent porosity after the removal of guest solvent molecules based on variable temperature powder X-ray diffraction and gas adsorption analysis. These materials exhibit similar gas adsorption properties, especially highly selective CO2 uptake/capture over other gases (N2 and CH4). However, because of the presence of an unsaturated Lewis acidic metal site, 2 acts as a very efficient heterogeneous catalyst toward the chemical conversion of CO2 to cyclic carbonates under mild conditions, whereas 1 shows very less activity. This work provides experimental evidence for the postulate that an unsaturated metal site in MOFs enhances adsoprtion of CO2 and promotes its conversion via the Lewis-acid catalysis.

Polar Sulfone-Functionalized Oxygen-Rich Metal-Organic Frameworks for Highly Selective CO2 Capture and Sensitive Detection of Acetylacetone at ppb Level.

A rational combination of an oxygen-rich pyridyl substituted tetrapodal ligand, tetrakis(4-pyridyloxymethylene)methane (TPOM), and a polar sulfone-functionalized conjugated bent dicarboxylate linker, dibenzothiophene-5,5'-dioxide-3,7-dicarboxylic acid (H2(3,7-DBTDC)), with d10 metal centers, Zn(II) and Cd(II), has led to the construction of two new three-dimensional (3D) metal-organic frameworks,{[Zn2(TPOM)(3,7-DBTDC)2]·7H2O·DMA}n (1) and {[Cd2(TPOM)(3,7-DBTDC)2]·6H2O·3DMF}n (2). Single-crystal X-ray analysis indicates that 1 is a 3D framework with a dinuclear repeating unit having two different Zn(II) centers (tetrahedral and square pyramidal) and 2 is a 3D framework comprised of a dinuclear repeating unit with one crystallographically independent distorted pentagonal bipyramidal Cd(II) coordinated to chelating/bridging carboxylates and nitrogen atoms of the TPOM ligand. In both cases, the pores are aligned with oxygen atoms of the TPOM ligand and decorated with polar sulfone moieties. On the basis of the stability established by thermogravimetric analysis and powder X-ray diffraction (PXRD) and the presence of large solvent accessible voids (25.4% for 1 and 40.6% for 2), gas sorption studies of different gases (N2, CO2, and CH4) and water vapor have been explored for both 1 and 2. The CO2 sorption isotherm depicts type I isotherm with an uptake of 93.6 cm3 g-1 (for 1) and 100.6 cm3 g-1 (for 2) at 195 K. Additionally, sorption of CO2 is highly selective over that of N2 and CH4 for both 1 and 2 due to the strong quadrupolar interactions between sulfone moieties and CO2 molecules. Configurational bias Monte Carlo (CBMC) molecular simulation has further justified the highly selective CO2 capture. On the other hand, the luminescence nature of 1 and 2 has been employed for highly selective detection of acetylacetone in aqueous methanol with a limit of 59 ppb in 1 and 66 ppb in 2, which are among the best reported values so far in the literature. The Stern-Volmer plots, spectral overlap, density functional theory calculations, CBMC simulation, and time-resolved lifetime measurements have been utilized for an extensive mechanistic study. The exclusive selectivity for acetylacetone in 1 and 2 have been confirmed by competitive selectivity test. Both exhibited good recyclability and stability after sensing experiments analyzed by fluorescence, PXRD, and field emission scanning electron microscopy studies.

Strategic Construction of Highly Stable Metal-Organic Frameworks Combining Both Semi-Rigid Tetrapodal and Rigid Ditopic Linkers: Selective and Ultrafast Sensing of 4-Nitroaniline in Water.

In this work, we have designed two new 3D metal-organic frameworks (MOFs), {Zn4(TPOM)(1,4-NDC)4} n (1) and {Ni2(TPOM)(1,4-NDC)2(H2O)2} n (2), utilizing both semi-rigid tetrapodal neutral linker, tetrakis(4-pyridyloxymethylene)methane (TPOM) and rigid ditopic anionic linker, 1,4-naphthalene dicarboxylic acid (H2(1,4-NDC)). On the basis of the single-crystal X-ray diffraction, 1 has a 3D structure with star-shaped pores arising from four-fold symmetry due to the presence of a paddle-wheel core [Zn2(O2CC12H6)4(C6H4N)2] as a subunit, whereas 2 consists of a zig-zag 3D framework with strong hydrogen bonding between the coordinated water molecules and coordinated carboxylate groups. Their thermogravimetric analysis indicates an extraordinary thermal stability: 1 up to 400 °C and 2 up to 350 °C. In addition to elemental microanalysis and spectroscopic characterization (UV-vis and infra-red spectroscopy), the bulk phase purity of 1 and 2 as well as hydrolytic stability of 1 are established by powder X-ray diffraction. Exploiting the luminescence nature of 1, both solvent-dependent fluorescence properties and sensing of various amines in aqueous medium are demonstrated. It exhibits good sensing ability toward 4-nitroaniline (4-NA) and 2,6-dichloro-4-nitroaniline (2,6-DCNA; a broad spectrum pesticide belonging to toxicity class III) with the lowest detection limit of 88 ppb and 0.28 ppm, respectively. The mechanism of action has been established through Stern-Volmer plots, time-resolved fluorescence studies, spectral overlap, and density functional theory calculations. The recyclability and stability of 1 after sensing experiments also reveal no change in its crystallinity. Furthermore, selectivity test and time-dependent detection for 4-NA have been successfully demonstrated. For practical applications, naked eye detection of 4-NA using test paper strips is also displayed.

Highly Selective Gaseous and Liquid-Phase Separation over a Novel Cobalt(II) Metal–Organic Framework

The mild recognition sites of oxygen atoms and phenyl rings from 5-(4-pyridyl)-methoxyl isophthalic acid (5,4-PMIA2-) moieties and tetrakis(4-pyridyloxymethylene) methane (TPOM) linkers inside the channels of a novel three-dimensional microporous metal-organic framework (MOF) [Co2(5,4-PMIA)2(TPOM)0.5]· xsolvent (1) are presumed to provide pore environments with moderate contacts toward guests, as indicated by grand canonical Monte Carlo simulations, which appear to be beneficial for adsorption and separation applications. As expected, 1 represents one of the rare examples that show both high storage capacity of C2H n and good adsorption selectivity of C2H n/CH4 and CO2/CH4 under ambient conditions, and yet, it has significantly lower energy consumption for regeneration. In addition, a validated submicro-1-based microsolid-phase extraction (μ-SPE) method for the determination of trace monohydroxylated polycyclic aromatic hydrocarbons in complex human urine was developed with satisfactory sensitivity and good precision by online coupling to liquid chromatography-mass spectrometry, which represents the first example of a mixed-ligand MOF applied as an efficient sorbent for μ-SPE.

An unprecedented acid/base stable Cu-based metal–organic framework with good catalytic activity for the reduction of 4-nitrophenol

A new 3D metal–organic framework with pcu topology {[Cu2(TPOM)(ddpa)2]}n (1) was synthesized under solvothermal condition by employing flexible tetrakis(4-pyridyloxymethylene) methane (TPOM) and semirigid 4,4′-dicarboxydiphenylamine (H2ddpa) as well as Cu(II) ion. Complex 1 exhibits good endurance in acid/base aqueous solutions and a high catalytic activity for the reduction of 4-nitrophenol in excess NaBH4 solution.

Photochemical and Magnetic Properties of Seven New Metal–Organic Frameworks Constructed by Flexible Tetrapyridines and V-Shaped Polycarboxylate Acids

Seven two- or three-dimensional (2D or 3D) coordination polymers have been synthesized by tetrakis(4-pyridyloxymethylene)methane (TPOM) with V-shaped 4,4′-oxybis(benzoicacid) (H2oba), 4,4′-sulfonyldibenzoic acid (H2sdb), 4,4′-(hexafluoroisopropylidene)bis(benzoic acid) (H2hfipbb), 4,4′-dicarboxydiphenylamine (H2ddpa), and 4,4′-dicarboxy-ethyl diphenylamine (H2dedpa) in the presence of nitrates of transition metal in H2O/DMF systems, namely, {[Co2(TPOM)(oba)2(H2O)2]·(H2O)8}n (1), {[Cd2(TPOM)(oba)2(H2O)2]·(H2O)4(DMF)1.5}n (2), {[Ni2(TPOM)(oba)2(H2O)2]·(H2O)5}n (3), {[Co2(TPOM)(hfipbb)2]·(H2O)3}n (4), {[Cd2(TPOM)(dedpa)2]·(H2O)4(DMF)2}n (5), {[Co2(TPOM)(sdb)2]·(H2O)3}n (6), {[Co2(TPOM)(ddpa)2]}n (7). Complexes 1–3 have similar structures, possessing 3D self-penetrated frameworks. Complex 4 is also a self-penetrated 3D framework containing meso-helix [Co(hfipbb)]n chains. Complex 5 reveals a 2-fold interlocked 2D → 2D network. For complex 6, only three pyridyl groups coordinated to Co(II) ions in one TPOM ligand, while for complex 7, only two pyridyl groups coordinated to Co(II) ions in one TPOM ligand. In addition, magnetic, fluorescence, and UV–vis properties of these complexes have been studied.

Syntheses, characterization, and properties of five coordination compounds based on the ligand tetrakis(4-pyridyloxymethylene)methane

Based on tetrakis(4-pyridyloxymethylene)methane (TPOM) and different carboxylates, five new MOFs with structures of high dimension and mutual interpenetration have been successfully synthesized.

Syntheses, Structures, and Characteristics of Four New Metal–Organic Frameworks Based on Flexible Tetrapyridines and Aromatic Polycarboxylate Acids

Solvothermal reactions of tetrakis(4-pyridyloxymethylene)methane (TPOM) with deprotonated isophthalic acid (1,3-H2bdc), 5-hydroxyisophthalic acid (5-OH-H2bdc), benzene-1,3,5-tricarboxylic acid (H3btc), and benzene-1,2,4,5-tetracarboxylic acid (H4btc) in the presence of zinc and cobalt salts produce four new complexes, namely, {[Co2(TPOM)(bdc)2(H2O)2]·(H2O)3}n (1), {[Zn2(TPOM)(5-OH-bdc)2]·(DMF)(H2O)2}n (2), {[Co3(TPOM)(btc)2(H2O)]·(H2O)4}n (3), and {[Zn2(TPOM)(btc)2]n (4). Complexes 1 and 2 possess similar 2-fold interpenetrating three-dimensional (3D) framework with bbf topology, but 1 crystallizes in an achiral space group, and 2 crystallizes in chiral space group and displays ferroelectric behavior. Complex 3 reveals a 3D framework with biunclear Co clusters, which displays weak antiferromagnetic character. In complex 4, only H4btc links Zn(II) to generate a 3D porous framework, with TPOM occupying the void space as countercation and template. In addition, photochemical and ferroelectric properties of t...

A homochiral diamond framework constructed from Fe(iii) and Mn(ii) oxo-clusters supported by Sb(iii) tartrate scaffolds

A homochiral diamond framework was obtained by using a secondary building unit (SBU) comprising an oxo-cluster containing 4Fe(III) and 3Mn(II) ions supported by Sb(3)O tartrate scaffolds. A fully protonated tetratopic cation, tetrakis(4-pyridyloxymethylene)methane (TPOM), acts as a template to arrange the clusters on a diamond lattice.

Temperature-controlled synthesis of two novel coordination polymers modeled by semi-rigid tetrapyridines

Solvothermal reactions of tetrakis(4-pyridyloxymethylene)methane (TPOM) with deprotonated benzoate (L1) in the presence of acetate (L2) of copper in H2O/CH3OH with reactant ratio 1 : 2 : 2 under different synthesis temperatures produced two new complexes, namely, {[Cu2(TPOM)2(L1)2(L2)2]·Guest}n (1), and {[Cu4(TPOM)(L1)2(L2)4(OH)2]·6H2O}n (2). These complexes were characterized by elemental analysis, IR spectroscopy, and X-ray single-crystal diffraction. Complex 1 reveals a 3D crystal structure with a novel 2,3,4-connected 3-nodal topology constructed from the connection of Cu centers and TPOM ligands, which neutralized the mono-dentate carboxylates from different ligands coordinated to Cu ions. Complex 2 exhibits a distinct 3D framework with 2-nodal PtS topology, constructed from the connection of neutral Cu4 SBUs and TPOM ligands. The increasing reaction temperature must be responsible for the versatile coordination modes of carboxylates in 2 compared to the ones in 1, resulting in the formation of the distinct crystal structure. In addition, magnetic investigations on complex 2 revealed antiferromagnetic intra-tetramer interactions through the mixed hydroxo and carboxylato bridges.

Syntheses, Structures, and Photoluminescence of Five New Metal−Organic Frameworks Based on Flexible Tetrapyridines and Aromatic Polycarboxylate Acids

Solvothermal reactions of tetrakis(4-pyridyloxymethylene)methane (TPOM) with deprotonated 1,4-benzenedicarboxylate (H2bdc) or 5-hydroxyisophthalic acid (5-OH-H2bdc) in the presence of nitrates of cadmium, zinc, and cobalt in H2O or H2O/DMF produced five new complexes, namely, {[Cd2(TPOM)(bdc)2]·(H2O)5(DMF)}n (1), {[Zn2(TPOM)(bdc)2]·(H2O)4}n (2), {[Zn2(TPOM)(bdc)2]·(H2O)}n (3), {[Co2(TPOM)(5-OH-bdc)2(H2O)2]·(H2O)5}n (4), and {[Cd2(TPOM)(5-OH-bdc)2]·(H2O)2}n (5). These complexes were characterized by elemental analysis, IR spectroscopy, and X-ray single-crystal diffraction. Complex 1 reveals a 2-fold interpenetrating three-dimensional (3D) framework with pcu topology constructed from binuclear Cd clusters and TPOM ligands. In addition, the experiment of single-crystal-to-single-crystal (SC-SC) structural transformations upon guest exchange was tested. Zn complexes 2 and 3 possess different 3D frameworks and are prepared from TPOM and H2bdc under different reaction conditions. In complexes 4 and 5, TPOM and 5-OH-H2bdc link Co or Cd centers to generate 3D interpenetrating frameworks with bbf and qtz topology. In addition, thermal stabilities and photochemical properties of these new complexes in the solid state have been studied.

Organization of Tetrahedral Chalcogenide Clusters Using a Tetrahedral Quadridentate Linker

Using predesigned tetrahedral quadridentate linker tetrakis(4-pyridyloxymethylene)methane (TPOM) as the organic linker, tetrahedral P1 clusters ([Cd8S(SPh)16](2-)) and C1 clusters ([Cd17S4(SPh)28](2-)) have been assembled into beltlike (MCOF-9) or chainlike (MCOF-10) configurations, as determined by single-crystal X-ray diffraction. The onset of optical absorptions of MCOF-9 and MCOF-10 is around 400 and 420 nm, respectively. The thermal analysis shows that both materials are stable up to 250 degrees C.