Porous Metal-organic Framework Materials Research Articles

ZnO@ZIF-8 Core-Shell Structure Gas Sensors with Excellent Selectivity to H2.

As the energy crisis becomes worse, hydrogen as a clean energy source is more and more widely used in industrial production and people’s daily life. However, there are hidden dangers in hydrogen storage and transportation, because of its flammable and explosive features. Gas detection is the key to solving this problem. High quality sensors with more practical and commercial value must be able to accurately detect target gases in the environment. Emerging porous metal-organic framework (MOF) materials can effectively improve the selectivity of sensors as a result of high surface area and coordinated pore structure. The application of MOFs for surface modification to improve the selectivity and sensitivity of metal oxides sensors to hydrogen has been widely investigated. However, the influence of MOF modified film thickness on the selectivity of hydrogen sensors is seldom studied. Moreover, the mechanism of the selectivity improvement of the sensors with MOF modified film is still unclear. In this paper, we prepared nano-sized ZnO particles by a homogeneous precipitation method. ZnO nanoparticle (NP) gas sensors were prepared by screen printing technology. Then a dense ZIF-8 film was grown on the surface of the gas sensor by hydrothermal synthesis. The morphology, the composition of the elements and the characters of the product were analyzed by X-ray diffraction analysis (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), Brunauer-Emmett-Teller (BET) and differential scanning calorimetry (DSC). It is found that the ZIF-8 film grown for 4 h cannot form a dense core-shell structure. The thickness of ZIF-8 reaches 130 nm at 20 h. Through the detection and analysis of hydrogen (1000 ppm), ethanol (100 ppm) and acetone (50 ppm) from 150 °C to 290 °C, it is found that the response of the ZnO@ZIF-8 sensors to hydrogen has been significantly improved, while the response to ethanol and acetone was decreased. By comparing the change of the response coefficient, when the thickness of ZIF-8 is 130 nm, the gas sensor has a significantly improved selectivity to hydrogen at 230 °C. The continuous increase of the thickness tends to inhibit selectivity. The mechanism of selectivity improvement of the sensors with different thickness of the ZIF-8 films is discussed.

Introduction of continuous excited-state intermolecular proton transfer process into open yttrium-terephthalate framework for ratiometric fluorescent fluorion detection

Fluorion detection has drawn great attention due to fluorides are usually toxicity but widely involved in chemical, industrial and biological processes. Considering the porosity of porous metal-organic framework (MOF) materials and fluoride ions may strongly influence the excited state intramolecular proton transfer (ESIPT) process, we propose that the introduction of ESIPT into MOFs should be promising for high-efficient fluorescence sensing of fluorions. In this work, the utilization of 2,5-dihydroxy terephthalic acid (DHBDC) with a pair of intramolecular hydrogen bonds as organic ligands led to a novel open yttrium-terephthalate framework (SNNU-300) as ESIPT-MOF fluorescence probe. Notably, the unique continuous ESIPT processes in the confined channels of SNNU-300 contribute a distinctive binate ratiometric fluorescent characteristics for fluoride ion detection. Quantitative fluorescence fluorion sensing experiments indicate SNNU-300 probe has high selectivity and sensitivity (Ksv ​= ​2.3 ​× ​104 ​M−1) and extra-low LOD value (1.2 ​× ​10−6 ​M). Also, fast detection, strong anti-interference ability and good reusability make SNNU-300 MOF a promising fluorion sensor in practical applications.

Ultrahigh Hydrogen Uptake in an Interpenetrated Zn 4 O-Based Metal–Organic Framework

As a highly promising candidate for hydrogen storage, crucial to vehicles powered by fuel cells, metal–organic frameworks (MOFs) have attracted the attention of chemists in recent decades. H2 uptak...

Metal-Organic Framework (MOF) Derived Recyclable, Superhydrophobic Composite of Cotton Fabrics for the Facile Removal of Oil Spills.

Marine oil spill cleanup is one of the major challenges in recent years due to its detrimental effect on our ecosystem. Hence, the development of new superhydrophobic oil absorbent materials is in high demand. The third-generation porous materials, namely metal-organic frameworks (MOFs), have drawn great attention due to their fascinating properties. In this work, a superhydrophobic MOF with UiO-66 (SH-UiO-66) topology was synthesized strategically with a new fluorinated dicarboxylate linker to absorb oil selectively from water. The fully characterized superhydrophobic MOF showed extreme water repellency with an advancing water contact angle (WCA) of 160° with a contact angle hysteresis (CAH) of 8°. The newly synthesized porous MOF (SBET = 873 m2 g-1) material with high WCA found its promising application in oil/water separation. The superhydrophobic SH-UiO-66 MOF was further used for the in-situ coating on naturally abundant cotton fiber to make a superhydrophobic MOF@cotton composite material. The MOF-coated cotton fiber composite (SH-UiO-66@CFs) showed water repellency with a WCA of 163° and a low CAH of 4°. The flexible superhydrophobic SH-UiO-66@CFs showed an oil absorption capacity more than 2500 wt % for both heavy and light oils at room temperature. The superoleophilicity of SH-UiO-66@CFs was further exploited to separate light floating oil as well as sedimentary heavy oil from water. SH-UiO-66@CFs material can also separate oil from the oil/water mixture by gravity-directed active filtration. Hence, the newly developed MOF-based composite material has high potential as an oil absorbent material for marine oil spill cleanup.

Supramolecular control of MOF pore properties for the tailored guest adsorption/separation applications

This work mainly focuses to review the recent progress of MOFs in different sorption and separation, and highlight the control approaches of the pore properties of MOFs on the capture and separation of the tailored guest molecules by various supramolecular interactions for the first time. • This review introduced the inherent pore properties of MOFs. • Some specific strategies are presented to improve the capture/separation of MOFs. • The supramolecular interactions are discussed between adsorbates and adsorbents. • The review prospected the sorption/separation applications of porous MOF materials. Because the adsorption/separation process plays a great role in chemical, petrochemical, pharmaceutical, environmental protection and many other fields, it has received extensive concern in both scientific research and practical applications. However, due to the new requirements and specific applications, it is a great necessity and urgency to explore new-type porous materials or maximize the adsorption capacity and improve the separation efficiency through endowing the adsorbent functionality to enable its special interactions with the adsorbates. The crystalline metal–organic framework (MOF) materials have shown great potentials in gas/liquid phase capture and separation due to their enormous porosities, tunable void properties, and easier modification, etc. Although there are lots of excellent reviews about functional MOFs in different fields, this review introduces the influence of MOF pore properties on the capture and separation of tailored guest molecules from the control of the supramolecular interactions for the first time. Some specific strategies are thus presented to enhance the adsorption/separation performance, and the relationships of the supramolecular interactions are well discussed between the adsorbates and adsorbents. Finally, the applications of porous MOF materials in adsorption/separation are further prospected and provided by the recent relevant studies.

BiOI Particles Confined into Metal-Organic Framework NU-1000 for Valid Photocatalytic Hydrogen Evolution under Visible-Light Irradiation.

Herein, a surface site engineering strategy is used to construct a porous Z-scheme heterojunction photocatalyst for photocatalytic hydrogen evolution (PHE) by integration of BiOI in a mesoporous Zr-based metal-organic framework (MOF) NU-1000. Three high-quality and highly dispersed BiOI@NU-1000 heterojunction materials are synthesized, and a set of methods is used to characterize these materials, indicating that the BiOI@NU-1000 heterojunction can retain high porosity and crystallinity of the parent NU-1000. Furthermore, the built-in electric field of the BiOI@NU-1000 composite can effectively tune the band gap, promote the separation of photoinduced charge carriers, improve photocurrent intensity, and reduce photoelectric impedance. Under visible-light irradiation, BiOI@NU-1000-2 showed the best photocatalytic performance in the field of MOF-based photocatalysts for PHE, with a hydrogen production rate of up to 610 μmol h-1 g-1. This study will open up opportunities for the construction of Z-scheme photocatalysts based on the highly porous MOF materials to inspire the development of innovative photocatalysts.

Porous Metal-Organic-Framework (MOF) Based Hybrid Materials for Thermoelectric Applications

Thermoelectric materials based on porous hybrid and MOFs constitute a very recent development, with many new and undiscovered phenomena for the research field. These porous Hybrid materials and MOF (Metal-Organic-Framework) films represent modern designer materials that exhibit many requirements of a near ideal and tunable future thermoelectric (TE) material. It is anticipated that especially the inherent porosity can be used advantageously in the design and simulation predictions of future thermoelectric materials. In principle, porous Hybrid and MOFs materials can comply with most of the requirements of an ideal and tunable future thermoelectric (TE) material. In contrast to traditional semiconducting bulk thermoelectric materials, porous hybrid MOF templates can be used to overcome some of the constraints of physics in bulk thermoelectric materials. These porous hybrid systems are amenable for simulation and modeling to design novel optimized electron-crystal phonon-glass materials with potentially very high Figure of Merit (ZT) numbers. Porous MOF and Hybrid materials possess an ultra-low thermal conductivity, which can be further modulated by phonon engineering within their complex porous and hierarchical architecture to advance the thermoelectric figure of merit ZT. This class of novel materials offers new approaches to the design of complex and hierarchical porous structures, possessing ultra-low thermal conductivity, which are able to trap, and localize phonons, thus resulting in a new generation of thermoelectric materials with a high ZT number. This work is demonstrating recent results of MOF thermoelectric Materials and provides a future outlook to the search for the next generation thermoelectric porous Hybrid and MOF materials, which could be part of a green renewable energy revolution with novel materials of sustainable high ZT values.

Study of Curcumin Adsorption of Nano Fe-based Metal-Organic Framework

Highly porous and biocompatible nano metal-organic framework materials (NMOF) are increasingly being applied in biomedical fields, especially as pharmaceutical adsorbent materials. Curcumin, found in turmeric, is a widely common herb in Eastern which has recently used in many applications in supporting cancer treatment. In the synthesis of MOF materials, the use of surfactants allows to control the morphology, the process of crystal formation and development and particle size of the material. In this research, MIL-100 (Fe) nanomaterials were successfully synthesized at room temperature in the presence of polyvinylpyrrolidone surfactant (PVP) to control the nanoparticle size about 50 nm in size. The synthesized MOF structure and properties were analyzed by using characterization techniques, including powder X-ray diffraction (PXRD), fourier-transform infrared (FT-IR), thermal gravimetric analyses (TGA) and nitrogen isothermal adsorption-desorption at 77 K. The characterization results showed that MIL-100 (Fe) nanomaterials have high crystallinity, large surface area, and highly thermal stability. However, its particle size is very small, only about 50 nm. Curcumin adsorption studies exhibited that this material had the ability to adsorb curcumin with an adsorption capacity up to 64.36 mg g-1. Kinetic and mechanism studies revealed that curcumin adsorption followed the pseudo-second model. In addition, thermodynamic studies proved that this was a spontaneous and exothermic adsorption process.

Application of metal-organic frameworks in the purification of indoor hexanal: Experiments and DFT calculations

Given that the toxic hexanal in indoor air is primarily originated from the cooking oil fumes, it is necessary to purify hexanal in the cooking oil fumes to prevent the adverse health effects of hexanal to human beings. In this study, four typical metal-organic frameworks (MOFs), namely MIL-101 (Cr), UiO-66, ZIF-8 and Cu-BDC were synthesized and applied to purify the indoor hexanal, and their adsorption capacities to hexanal were compared with the commercial activated carbon (AC). Our results show that the adsorption capacities of hexanal follow the order of MIL-101(Cr) (135 mg g−1)> UiO-66 (64.3 mg g−1)> ZIF-8 (40.3 mg g−1)> AC (35.8 mg g−1)> Cu-BDC (32.5 mg g−1), and the desorption capacities (by air) follow the order of MIL-101(Cr) (55.5 mg g−1)> UiO-66 (26.1 mg g−1)> AC (24.5 mg g−1)>ZIF-8 (19.3 mg g−1)> Cu-BDC (5.5 mg g−1), indicating that hexanal adsorbed on MIL-101 (Cr)/UiO-66 is more appropriate than the commercial AC to be desorbed.FTIR analysis confirms that O–H in Cr–OH/Zr–OH, O–C–O and aromatic C–H in H2BDC in both MIL-101 (Cr) and UiO-66 are possible sites for hexanal adsorption. DFT calculations further reveal that Cr–OH/Zr–OH and aromatic C–H in H2BDC are important sites to interact with CO in hexanal. This study provides a possibility to purify indoor aldehyde contaminants by the highly porous MOF materials.

Thermoelectric porous MOF based hybrid materials

Porous hybrid materials and MOF (Metal–Organic-Framework) films represent modern designer materials that exhibit many requirements of a near ideal and tunable future thermoelectric (TE) material. In contrast to traditional semiconducting bulk TE materials, porous hybrid MOF templates can be used to overcome some of the constraints of physics in bulk TE materials. These porous hybrid systems are amenable for simulation and modeling to design novel optimized electron-crystal phonon-glass materials with potentially very high ZT (figure of merit) numbers. Porous MOF and hybrid materials possess an ultra-low thermal conductivity, which can be further modulated by phonon engineering within their complex porous and hierarchical architecture to advance the TE figure of merit (ZT). This Perspective review discusses recent results of MOF TE materials and provides a future outlook and the vision to the search for the next generation TE porous hybrid and MOF materials, which could be part of the green renewable energy revolution with novel materials of sustainably high ZT values.

Ultrasound-assisted synthesis of a new nanostructured Ca(II)-MOF as 5-FU delivery system to inhibit human lung cancer cell proliferation, migration, invasion and induce cell apoptosis

A new porous metal-organic framework material, {Ca3(TATAB)2 (H2O)(MeOH)}(DMF)3}n (1, TATAB3- = 4,4′,4′′-s-triazine-1,3,5-triyltri-p-aminobenzoate), with considerable biocompatibility was synthesized by reaction of the Ca(NO3)2 and the H3TATAB ligand in DMF/MeOH solution. Nanostructure 1 can also be prepared by sonochemical process at ambient temperature. Nitrogen adsorption measurements revealed the presence of micropores as well as moderately high BET surface areas in the activated nanostructured 1 (1a). The incorporation of the drug 5-fluorouracil (5-FU) into 1a was 38.6 wt% per gram of 1a. 5-FU is released in a highly controlled and progressive fashion with 88.7% of the drug released after 72 h. The CCK8 assay was performed to evaluate the inhibitory effect of 5-FU@1a on NCI-H292 and NCI-H460 human lung cancer cells, and the transwell assay was conducted to observe the migration and invasion ability of cancer cells after 5-FU@1a treatment. The Annexin V-FITC/PI assay was carried out to evaluate the level of cancer cell apoptosis. The results above indicate 5-FU@1a has excellent anticancer activity in vitro. The in vivo xenograft model was applied, and the results suggested 5-FU@1a could reduce the volume and the weight of the tumor in vivo.

Modelling of porous metal-organic framework (MOF) materials used in catalysis

This paper presents a review of modern modelling of porous materials such as metal-organic frameworks used in catalysis. The authors’ own research approach using the nano-design of metal-organic frameworks is included in this review.

Influence of UiO-66(Zr) Preparation Strategies in Its Catalytic Efficiency for Desulfurization Process.

Porous metal-organic framework (MOF) materials UiO-66(Zr) obtained by solvothermal and microwave advanced synthesis (MWAS) procedures were characterized, and their catalytic efficiency was investigated for oxidative desulfurization (ODS) processes using a multicomponent model diesel containing benzothiophene and dibenzothiophene derivatives. The preparation parameters as the cooling time after oven use in the solvothermal procedure, and also the reaction time in the MWAS method seemed to play an important role in the catalytic performance of the UiO-66(Zr) material, as well as in its recycle capacity. The material prepared by the solvothermal procedure with a fast cooling time showed the best catalytic performance (desulfurization efficiency of 99.5% after 3 h). However, the application of the UiO-66(Zr) material prepared by the MWAS method (desulfurization efficiency of 96% after 3 h) conciliated a higher number of advantages, such as shorter reaction time preparation (15 min) and high catalytic activity for a higher number of reaction cycles. The UiO-66(Zr) prepared by the MWAS method was used for the first time in an oxidative desulfurization process, and according to the catalytic results obtained (high recycle capacity and stability) and shorter reaction time preparation, seems to be a promising material for industrial application.

Two-dimensional porous transition metal organic framework materials with strongly anchoring ability as lithium-sulfur cathode

Lithium-sulfur (Li-S) batteries are regarded as promising candidates for energy storage devices due to their high theoretical energy density. An ideal Li-S batteries cathode should effectively prevent polysulfide dissolution in order to achieve longer cycle life and higher rate performance. Herein, a new 2D transition metal organic framework material, hexaaminobenzene-based coordination polymers (HAB-CPs), has been systematically investigated as cathode candidate materials for Li-S batteries. First principles calculations combined with the vdW interaction and solvent model reveal that V-HAB-CP has the best ability to hinder the shuttle effect of lithium polysulfides among the three polymers (V, Cr and Fe-HAB-CPs). Quantum conduction (G) and density of states (DOS) calculations indicate that HAB-CPs maintain excellent conductivity during the whole charging process. Moreover, a very small volume change (about 3.06%) of V-HAB-CP before and after the electrode reaction can well deal with the volume expansion problem of Li-S batteries. Meanwhile, the energy density reaches 808.465 W h kg-1 when the electrode reaction product is Li16S8/V-HAB-CP. Attributed to these benefits, V-HAB-CP is a suitable cathode material, which is expected to be used in future Li-S battery systems. The computational method adopted in this paper can provide a guidance for considering the influence of electrolytes on the Li-S batteries in the future and be widely used in other simulation calculations involving the solution effect.

Structural basis of CO2 adsorption in a porous metal–organic framework material

Structural basis of CO₂ adsorption in a porous metal–organic framework material

Spectroscopic characterization of metal ligation in trinuclear iron-μ3-oxo-based complexes and metal-organic frameworks.

The adsorption-based functionalities of porous metal-organic framework (MOF) materials that lead to applications such as catalysis and gas separation rely on specific host-guest interactions often involving the framework metal sites. These interactions are difficult to probe on the molecular level and consequently poorly understood. Conventional X-ray absorption spectroscopy (XAS) methods can provide molecular-level insights but, as the sole method of characterization, often lack the ligand sensitivity required to probe the relevant local metal coordination changes associated with MOF adsorption processes. Here, we investigate a series of trinuclear iron μ3-oxo-based MOFs under different metal-coordinating guest environments (water, pyridine, propylene, and guest-free) using a multipronged spectroscopy approach, including valence-to-core X-ray emission spectroscopy (vtc-XES) along with conventional XAS and vibrational spectroscopy, in an effort to characterize their local metal site coordination environments, including ligand identity. Closely related iron μ3-oxo reference complexes with known coordination are characterized as well for comparison to evaluate the ligand diagnostic nature of the combined spectroscopy approach. Density functional theory calculations aid the vtc-XES band assignments and provide insights into the molecular orbital parentage of the vtc transitions. This series of MOFs and complexes illustrates the advantages and limitations of using this combination of complementary techniques for distinguishing subtle differences in framework metal node coordination environments.

Heterofullerene-linked metal–organic framework with lithium decoration for storing hydrogen and methane gases

Hydrogen and methane are considered as the promising fuels in the future, however, one of the obstacles to their utilizations is the lack of efficient storage and safe transportation materials. In this theoretical work, a novel kind of metal–organic framework (MOF) is designed using heterofullerene as linker from density functional theory calculations and first-principles molecular dynamics simulations. Based on grand canonical Monte Carlo simulations, we explore the adsorption performances of H2 and CH4 in the proposed porous MOF materials, which exhibit spectacular capacities for hydrogen storage as well as for methane storage after Li doping, both achieving the targets set by U.S. Department of Energy at workable conditions.

High Volumetric Hydrogen Adsorption in a Porous Anthracene-Decorated Metal-Organic Framework.

We report an unprecedented ligand-based binding domain for D2 within a porous metal–organic framework (MOF) material as confirmed by neutron powder diffraction studies of D2-loaded MFM-132a. A tight pocket of 6 Å diameter is formed by the close packing of three anthracene panels, and it is here rather than the open metal sites where D2 binds preferentially. As a result, MFM-132a shows exceptional volumetric hydrogen adsorption (52 g L–1 at 60 bar and 77 K) and the highest density of adsorbed H2 within its pores among all the porous materials reported to date under the same conditions. This work points to a new direction for H2 storage in porous materials using polyaromatic ligand-based sites.

Efficient prediction of water vapor adsorption capacity in porous metal–organic framework materials: ANN and ANFIS modeling

Optimum design of water vapor separation process (dehumidification) using adsorption process mostly depends on the selection of appropriate porous materials or adsorbents with the highest equilibrium storage capacity of the vapor. Equilibrium capacity is generally evaluated through cost-demanding experiments via direct measurement of the vapor isotherm. Reliable prediction of the vapor adsorption capacity in porous materials provides a robust tool to a quick screening of porous materials appropriating for dehumidification process. In this article, adsorption capacity of water vapor in metal–organic framework (MOF) materials is predicted using two robust “artificial neural network (ANN)” and “Adaptive network-based fuzzy inference system (ANFIS)” methods. The three parameters of the surface area, pore volume and pore diameters are selected as input and the water vapor adsorption capacities of MOFs were computed as the output of the models. Comparison of the obtained results and real experimental data implied the superiority of the ANFIS and ANN models to predict the water vapor adsorption capacity into MOFs with a mean squared error (MSE) of 0.005 and 0.002, respectively. This clearly indicates a great potential for the application of both ANN and ANFIS methods to rapid screen MOFs suitable for water vapor adsorption.

Multifunctional Gas Adsorption and Photocatalytic Degradation Based on a Porous Metal-Organic Framework Material

The reaction of Cu(NO3)2 · 3H2O with rigid ligand 4'-(1H-tetrazol-5-yl)-[1,1'-biphenyl]-3,5-dicarboxylic acid (H3L) gave a new metal-organic framework of [Cu2(μ3-OH)(L)(H2O)2] n (I) (CIF file CCDC no. 1533273). Complex I has a truncated cuboctahedra that was connected by trigonal Cu3O(N4CR)3 trimers using each tetrazolate (N4CR) moiety and shows a overall 3D nnt net with (6.82)6(83)2(62.84)3 topology. The properties of gas adsorption and the degradation of the methyl violet have been examined.