Isostructural Metal-organic Frameworks Research Articles

Zinc-based 1D coordination polymer for selective luminescent detection of nitrofuran antibiotics at part-per-billion level

With the harm caused by the misuse of antibiotics, the problem of water pollution has attracted much attention. Besides, water resources are closely related to human health. Therefore, the development of efficient and rapid methods for the detection of antibiotics is an important and urgent task. Here, a series of isostructural metal–organic framework materials (SYUCT-M, M = Zn, Co) was synthesized, SYUCT-Zn demonstrated sensing properties for efficient detection of nitrofuran antibiotics (NFAs). The detection limits of nitrofurazone (NFZ), furazolidone (FZD) and nitrofurantoin (NFT) by SYUCT-Zn were 1.47 ppb, 1.73 ppb and 2.43 ppb, respectively. Meanwhile, a fast response time and anti-interference ability of SYUCT-Zn is outstanding for 12 antibiotics in 5 classes. Apart from the sensitivity and selectivity, SYUCT-Zn featured excellent stability in acidic, basic or organic solvent media. Recyclability of SYUCT-Zn sensor was established, which indicates its great potential as sensory material for antibiotics detection.

Direct Observation of Enhanced Iodine Binding within a Series of Functionalized Metal-Organic Frameworks with Exceptional Irradiation Stability.

Optimization of active sites and stability under irradiation are important targets for sorbent materials that might be used for iodine (I2) storage. Herein, we report the direct observation of I2 binding in a series of Cu(II)-based isostructural metal-organic frameworks, MFM-170, MFM-172, MFM-174, NJU-Bai20, and NJU-Bai21, incorporating various functional groups (-H, -CH3, - NH2, -C≡C-, and -CONH-, respectively). MFM-170 shows a reversible uptake of 3.37 g g-1 and a high packing density of 4.41 g cm-3 for physiosorbed I2. The incorporation of -NH2 and -C≡C- moieties in MFM-174 and NJU-Bai20, respectively, enhances the binding of I2, affording uptakes of up to 3.91 g g-1. In addition, an exceptional I2 packing density of 4.83 g cm-3 is achieved in MFM-174, comparable to that of solid iodine (4.93 g cm-3). In situ crystallographic studies show the formation of a range of supramolecular and chemical interactions [I···N, I···H2N] and [I···C≡C, I-C═C-I] between -NH2, -C≡C- sites, respectively, and adsorbed I2 molecules. These observations have been confirmed via a combination of solid-state nuclear magnetic resonance, X-ray photoelectron, and Raman spectroscopies. Importantly, γ-irradiation confirmed the ultraresistance of MFM-170, MFM-174, and NJU-Bai20 suggesting their potential as efficient sorbents for cleanup of radioactive waste.

Metal-organic frameworks with optimal pore cages for high Xe adsorption and efficient Xe/Kr separation

Separation of Xe/Kr mixtures obtained from the by-products of air separation is a paramount industrial process but still a formidable challenge due to the inherent inertness and close physicochemical properties of Xe and Kr. Herein we present two isostructural metal–organic frameworks (MOF), MIL-88B-tpt and MIL-88B-tpt-F, which were found to have high Xe uptake capacities and efficient Xe/Kr separation resulted from the suitable pore caged structures and pore sizes. Remarkably, MIL-88B-tpt exhibits a record-high Xe sorption capacity of 210.2 cm3 g−1 at 273 K and 1 bar. The highest Xe uptake and moderate Xe/Kr separation selectivity endow MIL-88B-tpt with high-performance Xe/Kr separation, ranking it among the best-performing MOF. The comparable Xe/Kr separation performance observed for the fluorinated version of MIL-88B-tpt-F and MIL-88B-tpt indicates the fluorine groups have a negligible effect on the Xe/Kr separation. Thus the efficient Xe/Kr separation for both MOF is mainly resulted from the optimal pore cages for Xe trapping and the well-matched pore sizes for Xe atom. The extensive Xe···framework interactions unveiled by computational simulations facilitate a strong binding affinity to Xe, thus leading to the highest Xe uptakes and efficient separation ability for both MOF.

Rational synthesis of two isostructural thiophene-containing metal-organic frameworks toward photocatalytic degradation of organic pollutants

In this work, thiophene moieties (as the crucial functional groups) have been successfully incorporated into the skeleton of metal–organic frameworks (MOFs) by using thienyl-substituted triazole ligands. Reaction of AgCF3SO3 with 3-phenyl-5-(2-thienyl)-1,2,4-triazole (PTTzH) or 3,5-bis(2-thienyl)-1,2,4-triazole (BTTzH) afforded two isostructural MOFs (AgTz-3 and AgTz-4) in gram-scale. AgTz-4 with higher thiophene content showed significantly stronger photocatalytic activity than AgTz-3 with lower thiophene content. Noteworthy, the photodegradation rate constants of AgTz-4 were 0.055 mg·L-1·min-1 for rhodamine B and 0.24 min−1 for salazosulfapyridine, which is comparable or even higher than some MOF-based materials reported in the literature. More importantly, AgTz-4 demonstrated good reusability and stability after four cycles of photodegradation. Our experimental results revealed that the enhanced photodegradation efficiency can be attributed to the increased light absorption capacity and optimized band structure of Ag-MOFs resulting from the introduction of thiophene groups into MOF structures.

From insulator to semiconductor: effect of host–guest interactions on charge transport in M-MOF-74 metal–organic frameworks

Here, we report an air-free approach to infiltrate isostructural metal–organic frameworks (MOFs), M-MOF-74 (M = Cu, Mn, Zn, Mg), with conjugated acceptor 7,7,8,8-tetracyanoquinodimethane (TCNQ).

A series of isostructural metal-organic frameworks for an enhanced electro-catalytic oxygen evolution reaction.

Three new isostructural MOFs (ZnTIA, CoTIA and CdTIA) were synthesized by the solvothermal synthesis of the organic linker 5-triazole isophthalic acid (5-TIA) with the transition metals Zn(II), Co(II) and Cd(II) in the presence of the structure directing agent tetramethyl ammonium chloride (TMA). These three MOFs were characterized thoroughly by ScXRD, PXRD, FT-IR, TGA, BET and SEM. They have excellent thermal and water stabilities. Among all these MOFs mentioned, pristine CoTIA exhibited excellent electrocatalytic activity toward the oxygen evolution reaction (OER). It exhibits a Tafel slope of 68.9 mV dec-1 with an overpotential of 337 mV at 10 mA cm-2 current density. The OER activity of the CoTIA MOF is relatively equivalent to that of the state-of-the-art catalyst (RuO2). Furthermore, the mechanical stability of crystalline ZnTIA, CoTIA and CdTIA MOFs was tested under ball mill pressure. The result showed that all the MOFs exhibit low tolerance to mechanical force because their structure was highly distorted or collapsed under such pressure, which is reflected by their poor electrocatalytic OER activity.

Electron Beam and Thermal Stabilities of MFM-300(M) Metal-Organic Frameworks

This work reports the thermal and electron beam stabilities of a series of isostructural metal-organic frameworks (MOFs) of type MFM-300(M), where M = Al, Ga, In, or Cr. MFM-300(Cr) was...

Bromine functionalization of metal–organic frameworks to improve ethane/ethylene separation

Metal–organic frameworks (MOFs) have undergone extensive study as ethane-selective adsorbents for ethane/ethylene (C2H6/C2H4) separation, a process currently conducted through energy-intensive cryogenic distillation in the petrochemical industry. Herein, we present the effect of functionalization using bromine, known for its high polarizability, on the C2H6-selective adsorption properties of MOF. This approach, based on the slightly larger polarizability of C2H6 compared to C2H4, was systematically investigated using three isostructural MOFs: DMOF-1, DMOF-1-Br, and DMOF-1-Br2, featuring 1,4-benzenedicarboxylate, 2-bromo-1,4-benzenedicarboxylate, and 2,5-dibromo-1,4-benzenedicarboxylate ligands, respectively. While their C2H6/C2H4 selectivity, based on the ideal adsorbed solution theory, increased (from 1.51 to 1.75 at 298 K and 100 kPa for the 1/1 (v/v) mixture) with the rising Br content, breakthrough experiments revealed that DMOF-1-Br achieves the highest high-purity (>99.95 %) C2H4 productivity (9.7 LSTP kg−1 at 298 K and 100 kPa for the 1/1 mixture and 22.2 LSTP kg−1 for the 1/15 mixture). This accomplishment is attributed to the appropriate bromine functionalization. Further insight into their C2H6-selective adsorption behavior was gained through canonical Monte Carlo and dispersion-corrected density functional theory simulations.

Assembly of two trinuclear-cluster-based metal-organic frameworks: Structures and methanol electro-oxidation properties

The direct methanol fuel cell (DMFC) is an efficient and non-polluting green energy conversion device. However, the electrocatalysts for the anodic methanol oxidation reaction (MOR) in DMFC are often precious metal catalysts, which suffer from high cost, poor stability, and easy deactivation. In this work, two isostructural metal-organic frameworks (MOFs) [M3(μ3-OH)(TATB)(Nic)2(H2O)2(DMA)] (M = Co, Ni) were successfully synthesized under solvothermal conditions. Both frameworks possess a unique trinuclear cluster [M3(μ3-OH)(COO)5] secondary building unit (SBU) and a rare binodal (3,7)-connected network. Due to the high density of metal sites and prominent pore system within CTGU-36-Ni, it can serve as an effective molecular electrocatalyst for MOR, while CTGU-36-Co is an inert material. Further experimental results showed that the introduction of conductive substances could lead to a significant increase in the MOR area activity of CTGU-36-Ni. This work not only provides a non-noble metal molecular MOR electrocatalyst but also opens a new vision for the design and application of crystalline materials in various energy conversion processes.

Rational pore-window size control in three Cu-MOFs with different pore environments for efficient capture of the greenhouse gas SF6

Effective SF6 gas storage and SF6/N2 mixture separations are extremely important in the industry. Herein, a series of isostructural metal-organic frameworks (MOFs), [Cu6(H2O)3(NTB)4(PYZ)1.5] (SNNU-202, H3NTB = nitrilotribenzoic acid, PYZ = pyrazine), [Cu12(H2O)3(NTB)8(PYZ)3(BPY)1.5] (SNNU-203, BPY = 4,4′-bipyridine) and [Cu6(NTB)4(DABCO)1.5(BPY)1.5] (SNNU-204, DABCO = 1,4-diazabicyclo[2.2.2]octane), with different pore window sizes have been explored for the adsorption and separation performance of sulfur hexafluoride. With stepwise partitioning of the pore window, the adsorption capacity for SF6 and separation of SF6/N2 mixture are gradually improved. Notably, the SF6 uptake value for SNNU-204 is 6.0 mmol g−1 and the amount of substance ratio of SF6-to-N2 uptake can be up to 29.8 at 298 K and 1 bar, surpassing most of top-performing MOFs reported. Ideal adsorbed solution theory (IAST) calculations and breakthrough curves demonstrated that SNNU-204 exhibited excelling separation performance. The stepwise pore window partition can create more micropores, and the aromatic ring of the inserted ligand also facilitates interaction with sulfur hexafluoride gas molecules, providing an important strategy for the application of MOFs in SF6 gas adsorption and separation.

A Microporous Metal‐Organic Framework with Unique Aromatic Pore Surfaces for High Performance C2H6/C2H4 Separation

AbstractDeveloping adsorptive separation processes based on C2H6‐selective sorbents to replace energy‐intensive cryogenic distillation is a promising alternative for C2H4 purification from C2H4/C2H6 mixtures, which however remains challenging. During our studies on two isostructural metal–organic frameworks (Ni‐MOF 1 and Ni‐MOF 2), we found that Ni‐MOF 2 exhibited significantly higher performance for C2H6/C2H4 separation than Ni‐MOF‐1, as clearly established by gas sorption isotherms and breakthrough experiments. Density‐Functional Theory (DFT) studies showed that the unblocked unique aromatic pore surfaces within Ni‐MOF 2 induce more and stronger C−H⋅⋅⋅π with C2H6 over C2H4 while the suitable pore spaces enforce its high C2H6 uptake capacity, featuring Ni‐MOF 2 as one of the best porous materials for this very important gas separation. It generates 12 L kg−1 of polymer‐grade C2H4 product from equimolar C2H6/C2H4 mixtures at ambient conditions.

A Microporous Metal-Organic Framework with Unique Aromatic Pore Surfaces for High Performance C2 H6 /C2 H4 Separation.

Developing adsorptive separation processes based on C2 H6 -selective sorbents to replace energy-intensive cryogenic distillation is a promising alternative for C2 H4 purification from C2 H4 /C2 H6 mixtures, which however remains challenging. During our studies on two isostructural metal-organic frameworks (Ni-MOF 1 and Ni-MOF 2), we found that Ni-MOF 2 exhibited significantly higher performance for C2 H6 /C2 H4 separation than Ni-MOF-1, as clearly established by gas sorption isotherms and breakthrough experiments. Density-Functional Theory (DFT) studies showed that the unblocked unique aromatic pore surfaces within Ni-MOF 2 induce more and stronger C-H⋅⋅⋅π with C2 H6 over C2 H4 while the suitable pore spaces enforce its high C2 H6 uptake capacity, featuring Ni-MOF 2 as one of the best porous materials for this very important gas separation. It generates 12 L kg-1 of polymer-grade C2 H4 product from equimolar C2 H6 /C2 H4 mixtures at ambient conditions.

Photonic crystals constructed by isostructural metal-organic framework films

Photonic crystals constructed by isostructural metal-organic framework films

Control of the pore chemistry in metal-organic frameworks for efficient adsorption of benzene and separation of benzene/cyclohexane

Control of the pore chemistry in metal-organic frameworks for efficient adsorption of benzene and separation of benzene/cyclohexane

A Palladium-Based MOF for the Preferential Sorption of Benzene.

Selective sorption of volatile aromatic compounds is a challenging issue for their total abatement. Despite the well-known affinity of palladium toward rich π systems, studies dedicated to volatile organic compound (VOC) capture with Pd(II)-based metal-organic frameworks (MOFs) are still very scarce. Intending to shed more light on this complex topic, this work compares the adsorption properties of two isostructural MOFs [Cu(2-pymo)2]n and [Pd(2-pymo)2]n and their selectivity for the sorption of linear, cyclic, or aromatic VOCs. The combination of both experimental and computational investigations highlights an increasing aromatic affinity over saturated hydrocarbons when palladium is chosen as a metal center (nBenzene/nn-hexane = 1.8 at 0.5 p/p0) in the MOF instead of copper (nBenzene/nn-hexane = 0.7 at 0.5 p/p0). Furthermore, [Pd(2-pymo)2]n clearly exhibits preferential adsorption of benzene over toluene (nBenzene/nToluene = 1.7 at 0.5 p/p0), due to the steric hindrance effects of the latter. The present results clearly underline the attractiveness of Pd-based MOFs for the design of selective aromatic adsorbents. Moreover, they also highlight the [Pd(2-pymo)2]n MOF as a relevant candidate for the selective capture of benzene, by a synergistic combination of both charge interactions and steric hindrance effects.

Oxidatively Doped Tetrathiafulvalene-Based Metal-Organic Frameworks for High Specific Energy of Supercapatteries.

Poor electrical conductivity and instability of metal-organic frameworks (MOFs) have limited their energy storage and conversion efficiency. In this work, we report the application of oxidatively doped tetrathiafulvalene (TTF)-based MOFs for high-performance electrodes in supercapatteries. Two isostructural MOFs, formulated as [M(py-TTF-py)(BPDC)]·2H2O (M = NiII (1), ZnII (2); py-TTF-py = 2,6-bis(4'-pyridyl)TTF; H2BPDC = biphenyl-4,4'-dicarboxylic acid), are crystallographically characterized. The structural analyses show that the two MOFs possess a three-dimensional 8-fold interpenetrating diamond-like topology, which is the first example for TTF-based dual-ligand MOFs. Upon iodine treatment, MOFs 1 and 2 are converted into oxidatively doped 1-ox and 2-ox with high crystallinity. The electrical conductivity of 1-ox and 2-ox is significantly increased by six∼seven orders of magnitude. Benefiting from the unique structure and the pronounced development of electrical conductivity, the specific capacities reach 833.2 and 828.3 C g-1 at a specific current of 1 A g-1 for 1-ox and 2-ox, respectively. When used as a battery-type positrode to assemble a supercapattery, the AC∥1-ox and AC∥2-ox (AC = activated carbon) present an energy density of 90.3 and 83.0 Wh kg-1 at a power density of 1.18 kW kg-1 and great cycling stability with 82% of original capacity and 92% columbic efficiency retention after 10,000 cycles. Ex situ characterization illustrates the ligand-dominated mechanism in the charge/discharge processes. The excellent electrochemical performances of 1-ox and 2-ox are rarely reported for supercapatteries, illustrating that the construction of unique highly dense and robust structures of MOFs followed by postsynthetic oxidative doping is an effective approach to fabricate MOF-based electrode materials.

Efficient Propylene/Ethylene Separation in Highly Porous Metal-Organic Frameworks.

Light olefins are important raw materials in the petrochemical industry for the production of many chemical products. In the past few years, remarkable progress has been made in the synthesis of light olefins (C2-C4) from methanol or syngas. The separation of light olefins by porous materials is, therefore, an intriguing research topic. In this work, single-component ethylene (C2H4) and propylene (C3H6) gas adsorption and binary C3H6/C2H4 (1:9) gas breakthrough experiments have been performed for three highly porous isostructural metal-organic frameworks (MOFs) denoted as Fe2M-L (M = Mn2+, Co2+, or Ni2+), three representative MOFs, namely ZIF-8 (also known as MAF-4), MIL-101(Cr), and HKUST-1, as well as an activated carbon (activated coconut charcoal, SUPELCO©). Single-component gas adsorption studies reveal that Fe2M-L, HKUST-1, and activated carbon show much higher C3H6 adsorption capacities than MIL-101(Cr) and ZIF-8, HKUST-1 and activated carbon have relatively high C3H6/C2H4 adsorption selectivity, and the C2H4 and C3H6 adsorption heats of Fe2Mn-L, MIL-101(Cr), and ZIF-8 are relatively low. Binary gas breakthrough experiments indicate all the adsorbents selectively adsorb C3H6 from C3H6/C2H4 mixture to produce purified C2H4, and 842, 515, 504, 271, and 181 cm3 g-1 C2H4 could be obtained for each breakthrough tests for HKUST-1, activated carbon, Fe2Mn-L, MIL-101(Cr), and ZIF-8, respectively. It is worth noting that C3H6 and C2H4 desorption dynamics of Fe2Mn-L are clearly faster than that of HKUST-1 or activated carbon, suggesting that Fe2M-L are promising adsorbents for C3H6/C2H4 separation with low energy penalty in regeneration.

Selective and moisture-sensitive degradation of bromocresol green for isostructural MOFs assembled with D-camphorate and bipyridine

A novel 2D manganese MOFs exhibits selective photodegradation of bromocresol green which can be promoted by moisture owing to the sensitivity for the Mn-O bonds. • Synthesis and characterization of 2D corrugated structure. • Selective photodegradation of BCG. • Promotion of degradation of BCG by Moisture owing to the sensitive of coordination bonds. Three new isostructural metal-organic frameworks, [M 2 (D-cam) 2 (4,4’-bpy)(H 2 O) 4 ] (D-cam 2- = D-camphorate, 4,4’-bpy = 4,4’-bipyridine, M = Mn ( 1-Mn ), Co ( 1-Co ), and Ni ( 1-Ni )), have been synthesized and fully characterized. The complexes, crystallizing in chiral space group, P 2 1 , are AA-stacking corrugated layers with hcb topological networks composed of homochiral coordination chains, M(D-cam), and auxiliary ligands. Notably, the solubility in water for three MOFs decrease in accordance with Irving-Williams series, indicating the good moisture-sensitivity for 1-Mn . Furthermore, the photolysis experiments of dyes reveal that only 1-Mn can catalyze the degradation of bromocresol green (BCG) rapidly and selectively, which can pave a way to explore more prolific functional MOFs in catalysis. CCDC: 2158741

Ion conduction in Na＋ containing ionogels based on the UiO-66 metal organic framework

▪ conducting materials are critical to the development of solid-state sodium batteries which may enable the use of sodium metal anodes. Ionogels are hybrid liquid–solid electrolytes that are made by embedding an ionic liquid into a suitable solid framework. In this study, ionogels based on the UiO-66 type metal organic framework (MOF) porous structure were prepared. Three isostructural MOFs were synthesized and used: (i) the UiO-66 material, (ii) an amine functionalized MOF (UiO-66- ▪ ) and iii) a hydroxyl functionalized MOF (UiO-66- ▪ ). A mixture of sodium bis(fluorosulfonyl)imide (NaFSI) and 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMIM-FSI) was embedded in the pores of the MOFs. FTIR and conductivity spectroscopy were used to asses the interaction of the mobile species with the MOF structure as well as ion transport and electric relaxation properties of the materials. We found that the conductivity of the ionogels is strongly influenced by the functionalized linker used. The UiO-66- ▪ -based ionogels present an encouraging conductivity increase trend when sodium ions are present, whereas the UiO-66- ▪ -based ionogels present the highest conductivity in the order of 0.3 mScm−1 at 293 K, albeit this is very likely due to highly mobile protons. While further studies are needed to understand which species are dominating the ion conduction, this investigation offers an insight into the behavior of MOF-based ionogels and may guide further work in the field.

Boron adsorption and isotopic separation from water by isostructural metal-organic frameworks MIL-100(M)

Adsorption has been expected to be promising for boron-containing water treatment, boron resources recovery and boron isotopic separation. Although metal-organic frameworks have been demonstrated to be potential adsorbent candidates, in-depth investigation of the structure-performance relationship remains insufficient. Herein, the performance and mechanism of boron adsorption and isotopic separation were systematically investigated with isostructural MOFs. Six isomorphic MIL-100(M) materials with metal species from the third main group (Al, Ga and In) and the fourth period (Sc, Cr and Fe) were solvothermally synthesized as boron adsorbents. Superior boron isotopic separation factors (S) with 10B preference and comparable boron adsorption capacity (Q) were observed through batch boron adsorption experiments, where MIL-100(Al) exhibited the highest S of 1.618 and MIL-100(Sc) achieved the largest Q of 8.74 g-B/mol-MOF. A high correlation between metal atomic radius and performance was revealed and a plausible mechanism was proposed for boron adsorption and isotopic separation involving the important role of the metal center through post-adsorption characterization. This study will pave the way for designing boron adsorbents with improved properties and promote the efficient utilization of boron resources in water.