Interpenetrated Metal Organic Framework Research Articles

A fivefold linker length reduction in an interpenetrated metal-organic framework via sequential solvent-assisted linker exchange.

A sequential solvent-assisted linker exchange (SSALE) method was used to contract the unit cell dimensions of an interpenetrated layer-pillared Zn-MOF. The 15.3 Å N,N'-di-4-pyridylnaphthalenetetracarboxydiimide (DPNDI) pillar was replaced stepwise by 9.4 Å trans-1,2-bis(4-pyridyl)ethene (BPE) and 2.8 Å pyrazine (PYZ). Notably, the sequential transformations lead to more than five times reduction in the linker size, which is the largest change in linker size by the SALE method so far.

A Single-Crystal to Single-Crystal Conversion Scheme for a Two-Dimensional Metal–Organic Framework Bearing Linear Cd3 Secondary Building Units

The single-crystal to single-crystal (SCSC) conversion of metal–organic frameworks (MOFs) represents a facile route to new MOFs with structures and functionalities that are challenging to obtain by direct synthesis. However, conversion products are often structurally limited for a given precursor. We herein report that a two-dimensional (2D) MOF featuring a linear Cd3 cluster secondary building unit (SBU) converts into one type of three-dimensional (3D) interpenetrated and two types of 3D non-interpenetrated MOFs upon reaction with dipyridyl ligands. One of the interpenetrated 3D MOFs, in turn, undergoes either ligand substitution to give isoreticular interpenetrated MOFs, or ligand addition to give a self-penetrated 3D MOF. This rich SCSC conversion library is made possible by the inclined nature of the Cd3 SBU with respect to the 2D plane of the starting material to create an anisotropic environment around the SBU.

Rational Design of Three Two-Fold Interpenetrated Metal–Organic Frameworks: Luminescent Zn/Cd-Metal–Organic Frameworks for Detection of 2,4,6-Trinitrophenol and Nitrofurazone in the Aqueous Phase

Through a dual-ligand strategy, three mixed ligands metal–organic frameworks (MOFs), namely, {[Zn2(Py2TTz)2(BDC)2]·2(DMF)·0.5(H2O)}n (1), {[Cd2(Py2TTz)2(BDC)2]·2(DMF)}n (2), and {[Co2(Py2TTz)2(BDC)2]·2(DMF)·0.5(H2O)}n (3) (where Py2TTz = 2,5-bis(4-pyridyl)thiazolo[5,4-d]thiazole, BDC = 1,4-benzenedicarboxylate, and DMF = N,N-dimethylformamide), were synthesized under solvothermal conditions. The single-crystal X-ray diffraction analyses reveal that the three MOFs possess similar 2-fold interpenetrated three-dimensional framework structures with pcu topology. The fluorescence properties of compounds 1 and 2 were investigated systematically. The results show that compounds 1 and 2 display good fluorescent properties, which can be efficiently quenched by a trace amount of nitroaromatics 2,4,6-trinitrophenol (TNP) and antibiotics nitrofurazone (NZF) in water media. The large Ksv value and small limit of detection demonstrate that compounds 1 and 2 can serve as good fluorescent sensors for TNP and NFZ detectio...

Near-White Light Emission from Lead(II) Metal-Organic Frameworks.

Reaction of bpy (bpy = 4,4'-bipyridine) with Pb(OAc)2·3H2O in DMF (DMF = dimethylformamide) afforded a metal-organic framework (MOF), [Pb2(μ-bpy)(μ-O2CCH3)2(μ-O2CCH3)2]·H2O (1). Reaction of bpy with Pb(O2CCF3)2 in a methanol and chloroform mixture furnished another MOF, [Pb(μ-bpy)(μ-O2CCF3)2]·1/2CHCl3 (2). However, the reaction of bpy with Pb(OAc)2·3H2O in the presence of trifluoroacetic acid in a similar reaction condition yielded a hydrogen-bonded zwitter-ionic complex of Pb(II), [Pb(bpy-H)2(O2CCF3)4] (3). All compounds have been characterized by single crystal X-ray crystallography, FT-IR, and 1H NMR spectroscopies. Compound 1 forms four heptacoordinated Pb(II) joined by (OCCH3)-O- linkages, resulting in a 3D noninterpenetrated MOF net with a four-connected uninodal sra (SrAl2) topology. However, in 2, tetra-connected Pb4(O2CCF3)8 cluster units are linked further through eight bpy ligands to furnish a doubly interpenetrated MOF with a new topology but having the very similar connectivity of 1, whereas 3 forms a zigzag hydrogen-bonded chain structure. The variation of carboxylate anions, pH of the reaction medium, and the ratio of the reactants profoundly affected the final topological structure of the compounds synthesized. The solid-state photoluminescence of 1-3 was investigated at room temperature. Interestingly 1, 2, and 3 achieved close to white light emission when excited at 329, 376, and 330 nm, respectively. The systematic understanding of the photophysical properties of analogous Pb-based compounds may open new perspectives for developing single-phase white-light-emitting materials using Pb(II) based MOFs.

Thermal Transport in Interpenetrated Metal–Organic Frameworks

In practice, the usefulness of metal–organic frameworks (MOFs) for many gas storage applications depends on their ability to rapidly dissipate the heat generated during the exothermic adsorption process. MOFs can be precisely designed to have a wide variety of architectures which can allow tuning their thermal conductivity. In this work, we use molecular dynamics simulations to investigate the effect of interpenetration on the thermal conductivity of MOFs. We find that the addition of a parallel thermal transport pathway yields a thermal conductivity nearly the sum of the two constituent frameworks. This relationship holds for a variety of interpenetrating MOFs with different atomic masses and a wide range of interframework interaction parameters. We show that both the strength and range of interactions between constituent frameworks play a significant role in framework mobility as well as framework coupling which can result in deviation from this relationship. We propose a simple model to predict thermal conductivity of the interpenetrated framework based on thermal conductivities of individual frameworks and an interframework interaction parameter which can account for this deviation.

Two interpenetrated metal–organic frameworks with a slim ethynyl-based ligand: designed for selective gas adsorption and structural tuning

Structural tuning and selective gas adsorption of two interpenetrated metal–organic frameworks using a slim ethynyl-based ligand were achieved.

Enhancing the stability and porosity of penetrated metal-organic frameworks through the insertion of coordination sites.

Guided by the insertion of coordination sites within ligands, an interpenetrated metal-organic framework NKU-112 and a self-penetrated framework NKU-113 were obtained. The two MOFs have similar cage-based framework structures, while NKU-113 reveals enhanced porosity and stability compared with NKU-112, owing to the self-penetrated structure induced by the additional chelating bipyridine moiety in the ligand. To the best of our knowledge, this is the first study that attempts to shift the structure topology of a MOF from interpenetrated to self-penetrated while achieving a delicate modulation of the location and distances within the penetrated structure by inserting new coordination sites.

A flexible doubly interpenetrated metal–organic framework with gate opening effect for highly selective C2H2/C2H4 separation at room temperature

A flexible doubly interpenetrated MOF is realized at room temperature, whose pore spaces could accommodate a significant amount of C2H2 at room temperature via the gate-opening effect but exclude C2H4 and C2H6 outside.

A series of porous interpenetrating metal–organic frameworks based on fluorescent ligands for nitroaromatic explosive detection

Four porous interpenetrated fluorescent MOFs based on π-electron-rich N-donor ligands can effectively detect nitroaromatic explosives and exhibit highly sensitive responses to 2,4,6-trinitrophenol.

Tuning the gate opening pressure of a flexible doubly interpenetrated metal-organic framework through ligand functionalization.

A functional doubly interpenetrated MOF [(Zn4O)2(MDCPB)6DMF]·3DMF·3H2O (JLU-Liu33F, H2MDCPB = 5-methyl-1,3-di(4-carboxyphenyl)benzene, DMF = N,N-dimethylformamide) with pcu topology has been solvothermally synthesized. JLU-Liu33F (F = functionalization) is the isostructural analogue of JLU-Liu33, which is constructed by -CH3 functional V-shaped ligand and a classical Zn4O cluster. Similar to the adsorption property of JLU-Liu33, JLU-Liu33F also exhibits breathing behavior upon N2 and CO2 adsorption at 77 and 195 K, respectively. However, due to the introduction of -CH3 functional groups, the interpenetration degree of JLU-Liu33F become closer to that of JLU-Liu33, which results in higher gate opening pressures for both N2 and CO2 adsorption. Moreover, the breathing behavior of JLU-Liu33F for C2H6 and C3H8 adsorption disappeares. Moreover, JLU-Liu33F also exhibits commendable selectivity for C2H2 over CH4.

A robust polyoxometalate-templated four-fold interpenetrating metal-organic framework showing efficient organic dye photodegradation in various pH aqueous solutions.

A Keggin-type polyoxometalate (POM)-templated metal-organic framework, [Cd(TTPB-4)(DMF)3]4[PMo12O40]2[HPMo12O40]·6DMF·4H2O (1), based on a newly designed linker of TTPB-4 [TTPB-4 = 1,3,5-tris(4-(4H-1,2,4-triazol-4-yl)phenyl)benzene], has been hydrothermally synthesized and characterized using IR, XRD, TGA, UV-Vis and photoluminescence spectra. Single-crystal X-ray crystallography reveals that 1 represents a unique POM-templated four-fold interpenetrated 3-D coordination network. The POM-templated MOF of 1 exhibits strong chemical stability that can withstand aqueous solutions of various pH-values (2-10). Particularly, 1 possesses excellent photodegradation activity and recyclability towards the organic dyes of Crystal Violet (CV) and Basic Red 2 in aqueous solutions with different pH values.

Interpenetrated metal–organic frameworks (MOFs) and their applications

Interpenetrated metal–organic frameworks (MOFs) and their applications

A Stable Amino-Functionalized Interpenetrated Metal-Organic Framework Exhibiting Gas Selectivity and Pore-Size-Dependent Catalytic Performance.

An amino-functionalized doubly interpenetrated microporous zinc metal-organic framework (UPC-30) has been solvothermally synthesized. UPC-30 can be stable at 190 °C and confirmed by powder X-ray diffraction. Gas adsorption measurements indicate that UPC-30 exhibits high H2 adsorption heat and CO2/CH4 separation efficiency. After the exchange of Me2NH2+ by Li+ in the channels, the H2 adsorption heat increased by 19.7%. Because of the existence of -NH2 groups in the channels, UPC-30 can effectively catalyze Knoevenagel condensation reactions with high yield and pore-size-dependent selectivity.

Chiral [Mo8O26]4- Polyoxoanion-Induced Three-Dimensional Architectures With Homochiral Eight-Fold Interpenetrated Metal-Organic Frameworks.

A pair of novel chiral compounds based on homochiral 8-fold interpenetrated metal-organic frameworks (MOFs) and chiral polyoxometalates (POMs), formulated as d-[Cu(4,4'-bipy)1.5]4[Mo8O26] (d-1) and l-[Cu(4,4'-bipy)1.5]4[Mo8O26] (l-1) (4,4'-bipy = 4,4'-bipyridine), have been successfully synthesized and characterized by single crystal X-ray diffraction, infrared, thermogravimetric analysis, elemental analysis, and solid circular dichroism spectra. Structural analysis indicates that two compounds are enantiomers. The connection of copper cations and 4,4'-bipy ligands generates helical infinite chains, while adjacent chains are further linked by Cu-N bonds to form a three-dimensional interpenetrating framework with a (10,3)-a topology. Interestingly, the chiral [Mo8O26]4- polyanions are encapsulated in the chiral MOFs via sharing the oxygen atoms. Both d- and l-[Cu(4,4'-bipy)1.5]4[Mo8O26] crystallize in chiral space group C2221. Additionally, two compounds represent new examples of chiral self-assembly.

A Flexible Doubly Interpenetrated Metal-Organic Framework with Breathing Behavior and Tunable Gate Opening Effect by Introducing Co2+ into Zn4O Clusters.

A Zn4O clusters based flexible doubly interpenetrated metal-organic framework [(Zn4O)2(DCPB)6DMF]·2DMF·8H2O (JLU-Liu33, H2DCPB = 1,3-di(4-carboxyphenyl)benzene, DMF = N,N-dimethylformamide) with pcu topology has been solvothermally synthesized. Because of its flexible structure, JLU-Liu33 exhibits a breathing behavior upon N2 and CO2 adsorption at low temperature, and C2H6 and C3H8 adsorption at 273 and 298 K. Furthermore, by adopting the direct synthesis method, two isomorphic compounds-JLU-Liu33L and JLU-Liu33H-have been obtained by partial substituting Zn with different amounts of Co into the JLU-Liu33 framework. The gas adsorption study of Co-doped materials reveals that the gate opening effect of JLU-Liu33 can be modulated by introducing different contents of Co2+ into Zn4O clusters. Meanwhile, with the increasing amount of Co2+, the adsorption amount and isosteric enthalpy values for CO2 have been improved. It is worth mentioning that JLU-Liu33H exhibits commendable selectivity for CO2 over CH4 which may be a good candidate for industrial gas purification and air separation applications.

Active Response of Six-Coordinate Cu2+ on CO2 Uptake in Cu(dpa)2SiF6-i from in Situ X-ray Absorption Spectroscopy

Interpenetrated metal organic framework (MOF) Cu(dpa)2SiF6-i (dpa = dipyridyl acetylene) with 6-coordinate copper takes up CO2 with isosteric heat of sorption Qst ≅ 40 kJ/mol, comparable to MOFs designed to have specific, strong chemisorption interactions. Although small pore size contributes to this high Qst, any preferred microscopic physisorption mechanisms were incompletely understood. We present in situ X-ray absorption spectroscopy results sensitive to local electronic structure around copper, fluorine, and nitrogen to look for signatures of CO2 interaction with and near ionic species in Cu(dpa)2SiF6-i. No changes in F or N K edge spectra imply no structural or electronic distortions to SiF62– or dpa molecules on CO2 uptake. Cu L2,3 edge spectra confirm Cu2+ valence and show weak systematic CO2-induced effects that result from distortions of the copper coordination shell. We suggest that electrostatic interaction between Cu2+ and axially aligned CO2 quadrupole moments contributes to the large Qst.

Interpenetrated Metal–Organic Frameworks of Cobalt(II): Structural Diversity, Selective Capture, and Conversion of CO2

Three new metal–organic frameworks (MOFs) of Co(II), [{Co(muco)(bpa)(2H2O)}·2H2O]n (1), [{Co(muco)(azopy)}·H2O]n (2), and [{Co(muco)(4bpdp)}·2DMF·H2O]n (3) (where, muco = trans, trans-muconate dianion, bpa = 1,2-bis(4-pyridyl)ethane, azopy = 4,4′-bisazobipyridine, and 4bpdb = 1,4- bis(4-pyridyl)-2,3-diaza-1,3-butadiene) have been synthesized and structurally characterized by single-crystal X-ray diffraction analysis. Structural analysis revealed that MOF1 exhibits an interesting 3-fold interpenetrated three-dimensional (3D) pillar-layered framework structure with 4-c, {66} topology, while 2 and 3 possess a 2-fold interpenetrated 3D pillar-layered framework structure with 7-c, {3∧3.4∧13.5∧4.6} net topology. Gas adsorption study of the compounds shows that 1 exhibits selective adsorption of CO2 over other (H2, N2, and Ar) gases with an uptake higher than those of 2 and 3. Further, the metal coordinated water molecules in MOF1 can be reversibly removed by high temperature treatment to generate a dehydrated f...

Topology Conversions of Non-Interpenetrated Metal–Organic Frameworks to Doubly Interpenetrated Metal–Organic Frameworks

Non-interpenetrated three-dimensional (3D) metal–organic frameworks (MOFs) with both an interpenetration-favorable (3,5)-c hms topology and an interpenetration-unfavorable (3,5)-c gra topology are converted to doubly interpenetrated analogues with hms-c topology by thermal treatment, even in the absence of solvent. Depending on the conversion temperature and the properties of the pillaring ligand in the non-interpenetrated 3D MOF, which is based on two-dimensional sheets with 3-c hcb topology pillared by neutral ditopic linkers, the pillaring ligands in the interpenetrated MOFs produced are partially removed during the thermal conversions, leading to interpenetrated MOFs that simultaneously contain both micro- and mesopores.

Partially Interpenetrated NbO Topology Metal–Organic Framework Exhibiting Selective Gas Adsorption

We report on the first partially interpenetrated metal–organic framework (MOF) with NbO topology for its ability to separate methane from carbon dioxide and permanently sequester the greenhouse gas CO2. The MOF, Cu2(pbpta) (H4pbpta = 4,4′,4″,4‴-(1,4-phenylenbis(pyridine-4,2-6-triyl))-tetrabenzoic acid), crystallizes in the monoclinic C2/m space group and has a 2537 m2/g Brunauer, Emmett and Teller surface area with an 1.06 cm3/g pore volume. The MOF exhibits selective adsorption of CO2 over CH4 as well as that of C2H6 and C2H4 over CH4. Cu2(pbpta) additionally shows excellent catalytic efficacy for the cycloaddition reaction of CO2 with epoxides to produce industrially important cyclic carbonates using solvent-free conditions.

ReaxFF Molecular Dynamics Simulations of Water Stability of Interpenetrated Metal–Organic Frameworks

Molecular dynamics (MD) simulations using the reactive force field (ReaxFF) have been performed to elucidate the underlying water-induced disruption mechanism of several prototypical interpenetrated MOFs (IRMOF-9, IRMOF-13, and SUMOF-4). Through the comparison to the corresponding noninterpenetrated MOFs (IRMOF-10 and IRMOF-14), for both the interpenetrated and noninterpenetrated MOFs, structural collapse was always accompanied by the dissociation of the water molecules, with the produced OH– and H+ forming chemical bonds with the Zn2+ ion and O atom of the ligand, respectively. However, the water stability of the interpenetrated MOFs is less than that of the corresponding noninterpenetrated structures. The reasons for the differences between the MOFs in the resistance to water attack are clarified. The water resistance of the noninterpenetrated MOFs is mainly attributed to the strength of the Zn–Oligand, but, the hydrogen bond has little effect. However, a trade-off between the strength of the Zn–Oligand...