Fluorinated Metal Organic Frameworks Research Articles

Hydrostable Fluorinated Metal–Organic Frameworks for CO2 Capture from a Wet Flue Gas: Multiscale Computational Screening

Hydrostable Fluorinated Metal–Organic Frameworks for CO₂ Capture from a Wet Flue Gas: Multiscale Computational Screening

Fluorinated ZIF-71 with adjusted pore size to enhance separation performance of mixed matrix membrane for recovering R32 from R410A

Due to the high Global Warming Potential (GWP) of hydrofluorocarbons (HFCs), the Kigali Amendment to the Montreal Protocol explicitly calls for the phase-out or limited use of HFCs, and the replacement of HFCs by hydrofluoroolefins (HFOs) is imminent. Therefore, it is particularly significant to develop new technology to separate valuable difluoromethane (R32, GWP = 675) from the near-azeotropic refrigerant blend R410A (GWP = 2088), because the traditional distillation is not applicable. In this work, aiming to enhance the separation performance of mixed matrix membrane (MMMs) for R410A, 5-fluorobenzimidazole was introduced into ZIF-71 by the solvent assisted linker exchange (SALE) method for the first time to reduce the pore size of fluorinated ZIF-71 by benzene rings and form hydrogen bonds between R32 with ZIF-71. A novel series of MMMs consisting of fluorinated ZIF-71 and Poly(ether-block-amide) ®1657 (Pebax®1657) polymer were prepared to separate the components of the R410A. The separation performance of the MMMs was investigated at different feed pressures and filler loading. The results showed that the introduction of 5-fluorobenzimidazole contributed to a significant increase in R32 permeability and R32/R125 selectivity of the MMMs compared to pure Pebax membrane. The 15 wt% ZIF-71-F/Pebax MMM showed the best separation performance with R32/R125 selectivity up to 26.6, four times that of pure Pebax membrane and twice that of ZIF-71/Pebax MMM. The ZIF-71-F/Pebax MMM have outstanding data on R32/R125 selectivity and no significant disadvantage in permeability, far exceeding the reported separation performance of membranes for R410A. This confirms that the application of fluorinated metal organic frameworks (MOFs) to the separation of refrigerant blends is a promising strategy.

Fluorinated Metal-Organic Frameworks with Dual-Functionalized Linkers to Enhance Photocatalytic H2 Evolution and High Water Adsorption.

Photocatalytic H2 evolution has recently attracted much attention due to the reduction of nonrenewable energy sources and the increasing demand for renewable sustainable energies. Meanwhile, metal-organic frameworks (MOFs) are emerging potential photocatalysts due to their structural adaptability, porous configuration, several active sites, and a wide range of performance. Nevertheless, there are still limitations in the photocatalytic H2 evolution reaction of MOFs with higher charge recombination rates. Herein, a copper-organic framework with dual-functionalized linkers {[Cu2(L)(H2O)2]·(5DMF)(4H2O)}n (fluorinated MOF(Cu)-NH2; H4L = 3,5-bis(2,4-dicarboxylic acid)-4-(trifluoromethyl)aniline) and with a rare 2-nodal 4,12-connected shp topology has been synthesized by a ligand-functionalization strategy and evaluated for the photocatalytic production of H2 to overcome this issue. According to the photocatalytic H2 evolution results, fluorinated MOF(Cu)-NH2 showed a hydrogen evolution rate of 63.64 mmol·g-1·h-1 exposed to light irradiation, indicating values 12 times that of the pure ligand when cocatalyst Pt and photosensitizer Rhodamine B were present. In addition, this MOF showed a maximum water absorption of 205 cm3·g-1. When dual-functionalized linkers are introduced to the structure of this MOF, its visible-light absorption increases considerably, which can be associated with nearly narrower energy band gaps (2.18 eV). More importantly, this MOF contributes to water absorption and electron collection and transport, acting as a bridge that helps to separate and transfer photogenerated charges while shortening the electron migration path because of the functional group in its configuration. The current paper seeks to shed light on the design of advanced visible-light photocatalysts with no MOF calcination for H2 photocatalytic production.

Facile decoration of fluorinated metal–organic frameworks on copper foil for regulated lithium deposition and robust solid electrolyte interface

Lithium metal is one of the most promising anode materials for Li-ion batteries. However, lithium metal anodes suffer from low coulomb efficiency, short cycle life, and even serious safety issues, owing to the incompatible Cu/Li interface and brittle solid electrolyte interface (SEI). A facile strategy is proposed to construct stable lithium metal anodes by regulating both the Cu/Li interface and SEI membrane with a thin layer of copper-tetrafluoroterephthalate (CuTFBDC), which can guide the uniform lithium deposition and the LiF-rich SEI. The prepared CuTFBDC@Cu foils can be applied as current collectors, and the assembled Li@CuTFBDC@Cu//Li symmetric cell exhibits a stable performance at a current density of 0.5 mA cm−2 for more than 3000 h, with a small voltage hysteresis of less than 11.5 mV, surpassing that of the bare Cu foil. The assembled Li@CuTFBDC@Cu//LFP (LiFePO4) full cell proceeds smoothly for 200 cycles at a current density of 2 C with a specific capacity of 133.8 mAh/g, and the capacity can be maintained at 125.29 mAh/g after 250 cycles. This facile strategy can provide a solution for both the Cu/Li interface and SEI membrane, showing an excellent prospect for practical applications in lithium metal batteries.

Fluorinated metal–organic frameworks for enhanced stability and iodine adsorption selectivity under humid conditions

The selective removal of radioactive iodine from off-gases of reprocessing plants with high humidity is crucial for environmental security, and the metal–organic framework (MOF)-based porous material is considered as one of the promising adsorbents. However, MOFs usually suffer from low structural stability and the competitive adsorption of water. Herein, fluorinated groups are introduced into MOFs to improve the iodine adsorption performance under humid conditions. Two different strategies, the ligand exchange and direct synthesis, were employed to construct fluorinated Zr-based PCN-222 and UiO-66, respectively. Both the two fluorinated MOFs exhibit enhanced structural stability when interacting with iodine guests, and thus the iodine adsorption capacity is improved due to the more stable pore structure. Besides, after fluorination, the iodine adsorption selectivity is also enhanced in the presence of high humidity. Particularly, UiO-66-F exhibits an iodine adsorption capacity of 0.93 g/g under wet iodine vapor with 18% RH at 80 ℃, close to that in the dry iodine vapor. DFT calculation and XPS analysis suggest there is no F…I halogen bonding interaction between fluorinated groups and trapped iodine, and the Zr nodes transfer negative charges to iodine via O-containing groups in the Zr nodes.

Recent advances in the chemistry and applications of fluorinated metal-organic frameworks (F-MOFs).

Metal-organic frameworks are a class of porous crystalline materials based on the ordered connection of metal centers or metal clusters by organic linkers with comprehensive functionalities. The interest in these materials is rapidly moving towards their application in industry and real life. In this context, cheap and sustainable synthetic strategies of MOFs with tailored structures and functions are nowadays a topic widely studied from different points of view. In this review, fluorinated MOFs (F-MOFs) and their applications are investigated. The principal aim is to provide an overview of the structural features and the main application of MOFs containing fluorine atoms both as anionic units or as coordinating elements of more complex inorganic units and, therefore, directly linked to the structural metals or as part of fluorinated linkers used in the synthesis of MOFs. Herein we present a review of F-MOFs reported in the recent literature compared to benchmark compounds published over the last 10 years. The compounds are discussed in terms of their structure and properties according to the aforementioned classification, with an insight into the different chemical nature of the bonds. The application fields of F-MOFs, especially in sustainability related issues, such as harmful gas sorption and separation, will also be discussed. F-MOFs are compounds containing fluorine atoms in their framework and they can be based on: (a) fluorinated metallic or semi-metallic anionic clusters or: (b) fluorinated organic linkers or (c) eventually containing both the building blocks. The nature of a covalent C-F bond in terms of length, charge separation and dipole moment sensibly differs from that of a partly ionic M-F (M = metal) one so that the two classes of materials (points a and b) have different properties and they find various application fields. The study shows how the insertion of polar M-F and C-F bonds in the MOF structure may confer several advantages in terms of interaction with gaseous molecules and the compounds can find application in gas sorption and separation. In addition, hydrophobicity tends to increase compared to non-fluorinated analogues, resulting in an overall improvement in moisture stability.

Synthesis of Hierarchical-Porous Fluorinated Metal-Organic Frameworks with Superior Toluene Adsorption Properties.

Constructing metal-organic frameworks (MOFs) with high volatile organic compounds (VOCs) adsorption capacity and excellent water resistance remain challenging. Herein, a monocarboxylic acid-assisted mixed ligands strategy was designed to synthesize a novel fluorinated MOFs, MIL-53 (Al). The monocarboxylic acid promoted crystallization and produced abundant crystal defects, which increased pore volume. Moreover, the competitive coordination between tetrafluoroterephthalic acid and 1,4-dicarboxybenzene was moderated by monocarboxylic modulators, significantly improving the hydrophobicity. The toluene uptake of the optimal sample reached 254.85 mg g-1 under humid conditions, increased by 33.56 % of MIL-53(Al), and the QWet /QDry (the ratio of adsorption quality under wet to adsorption quality under dry) was 0.92, remarkably surpassing that of origin MIL-53 (0.72). The recycle experiment showed superior reusability with no performance degradation after 10 recycle under RH=50 % (relative humidity). The adsorptive kinetic and thermodynamic analysis proves that the adsorption process is controlled by surface mono-layer adsorption and pore diffusion. The fluorine group affects the internal diffusion, which weakens the transfer rate. This strategy opens a new prospect of obtaining hierarchical functional MOFs for meeting the VOCs uptake under the practical application.

Fluorous Metal–Organic Frameworks with Unique Cage-in-Cage Structures Featuring Fluorophilic Pore Surfaces for Efficient C 2 H 2 /CO 2 Separation

Fluorous Metal–Organic Frameworks with Unique Cage-in-Cage Structures Featuring Fluorophilic Pore Surfaces for Efficient C ₂ H ₂ /CO ₂ Separation

Fluorinated metal-organic frameworks for gas separation.

Fluorinated metal-organic frameworks (F-MOFs) as fast-growing porous materials have revolutionized the field of gas separation due to their tunable pore apertures, appealing chemical features, and excellent stability. A deep understanding of their structure-performance relationships is critical for the synthesis and development of new F-MOFs. This critical review has focused on several strategies for the precise design and synthesis of new F-MOFs with structures tuned for specific gas separation purposes. First, the basic principles and concepts of F-MOFs as well as their structure, synthesis and modification and their structure to property relationships are studied. Then, applications of F-MOFs in adsorption and membrane gas separation are discussed. A detailed account of the design and capabilities of F-MOFs for the adsorption of various gases and the governing principles is provided. In addition, the exceptional characteristics of highly stable F-MOFs with engineered pore size and tuned structures are put into perspective to fabricate selective membranes for gas separation. Systematic analysis of the position of F-MOFs in gas separation revealed that F-MOFs are benchmark materials in most of the challenging gas separations. The outlook and future directions of the science and engineering of F-MOFs and their challenges are highlighted to tackle the issues of overcoming the trade-off between capacity/permeability and selectivity for a serious move towards industrialization.

Fluorinated metal organic frameworks, MFFIVE-Ni-L (M = Fe/Al, L = pyr), with coordinatively unsaturated metal site for CO2 separation from flue gas in the presence of humidity by computational methods.

The anthropogenic emission of greenhouse gases, mainly CO2, is considered to be one of the most challenging environmental threats related to global climatic change. Herein, for the first time, we accurately interpreted the interaction of guest molecules such as H2O, CO2 and N2, the main constituent of flue gas, to a coordinatively unsaturated (CUS) square pillared fluorinated metal organic framework (MOF) using a grand canonical Monte Carlo (GCMC) simulation with the help of a specific forcefield. This specific forcefield is derived from the interaction energy profile of the guest molecules to the framework attained from the periodic-density functional theory (DFT) calculations. The DFT-derived forcefield effectively safeguarded the ability of the coordinatively unsaturated square pillared fluorinated MOF for CO2 separation in the presence of moisture.

Nanoporous Fluorinated Metal–Organic Framework-Based Membranes for CO2 Capture

The search for effective carbon-capture materials has permitted the disclosure and institution of nanoporous fluorinated metal–organic frameworks (MOFs) with a contracted pore system as benchmark CO2-selective adsorbents. Namely, the SIFSIX-3-M (M = Zn, Cu, and Ni) MOF adsorbents, encompassing a periodic arrangement of fluorine moieties in a confined one-dimensional channels, exhibit a remarkable CO2 adsorption-based selectivity over CH4 and H2 in various industrially related gas mixtures. Here, we report the successful transplantation/integration of this distinctive CO2 selectivity, distinguishing this class of nanoporous MOF adsorbents to pure MOF membranes for carbon capture. Markedly, the liquid-phase epitaxy (LPE) growth approach permitted, for the first time, the building of continuous, homogeneous, and defect-free MOF membranes based on the SIFSIX-3-M platform, MSiF6(Pyz)2 with M = Ni or Cu, on a porous alumina substrate. Single and mixed-gas permeation tests revealed that the resulting nanoporous MOF membrane is a CO2-selective membrane, exhibiting the foreseen favorable CO2-selectivity toward carbon dioxide over H2, and CH4, governed by the CO2-selective adsorption in the functional and contracted channels of the SIFSIX-3-M.

Adsorption of Fluorocarbons and Chlorocarbons by Highly Porous and Robust Fluorinated Zirconium Metal-Organic Frameworks.

Fluorocarbons and chlorocarbons are common volatile organic compounds that pose serious risk to the environment and human health and therefore need to be effectively captured. Herein, we report a series of highly fluorinated metal-organic frameworks with high porosity (Brunauer-Emmett-Teller surface area ∼3000 m2/g) and stability. They show exceptionally high capacity and good recyclability toward the adsorption of fluorocarbons and chlorocarbons.

Fluorinated MOF platform for selective removal and sensing of SO2 from flue gas and air

Conventional SO2 scrubbing agents, namely calcium oxide and zeolites, are often used to remove SO2 using a strong or irreversible adsorption-based process. However, adsorbents capable of sensing and selectively capturing this toxic molecule in a reversible manner, with in-depth understanding of structure–property relationships, have been rarely explored. Here we report the selective removal and sensing of SO2 using recently unveiled fluorinated metal–organic frameworks (MOFs). Mixed gas adsorption experiments were performed at low concentrations ranging from 250 p.p.m. to 7% of SO2. Direct mixed gas column breakthrough and/or column desorption experiments revealed an unprecedented SO2 affinity for KAUST-7 (NbOFFIVE-1-Ni) and KAUST-8 (AlFFIVE-1-Ni) MOFs. Furthermore, MOF-coated quartz crystal microbalance transducers were used to develop sensors with the ability to detect SO2 at low concentrations ranging from 25 to 500 p.p.m.

Concurrent Sensing of CO2 and H2O from Air Using Ultramicroporous Fluorinated Metal-Organic Frameworks: Effect of Transduction Mechanism on the Sensing Performance.

Conventional materials for gas/vapor sensing are limited to a single probe detection ability for specific analytes. However, materials capable of concurrent detection of two different probes in their respective harmful levels and using two types of sensing modes have yet to be explored. In particular, the concurrent detection of uncomfortable humidity levels and CO2 concentration (400-5000 ppm) in confined spaces is of extreme importance in a great variety of fields, such as submarine technology, aerospace, mining, and rescue operations. Herein, we report the deliberate construction and performance assessment of extremely sensitive sensors using an interdigitated electrode (IDE)-based capacitor and a quartz crystal microbalance (QCM) as transducing substrates. The unveiled sensors are able to simultaneously detect CO2 within the 400-5000 ppm range and relative humidity levels below 40 and above 60%, using two fluorinated metal-organic frameworks, namely, NbOFFIVE-1-Ni and AlFFIVE-1-Ni, fabricated as a thin film. Their subtle difference in a structure-adsorption relationship for H2O and CO2 was analyzed to unveil the corresponding structure-sensing property relationships using both QCM- and IDE-based sensing modes.

Ultrasound-assisted synthesis of two new fluorinated metal-organic frameworks (F-MOFs) with the high surface area to improve the catalytic activity

Micro- and nano-structures of two zinc(II) based fluorinated metal-organic frameworks (F-MOFs) [Zn2(hfipbb)2(4-bpdh)].(DMF)0.5 (TMU-55) and [Zn2(hfipbb)2(4-bpdb)].(DMF)2 (HTMU-55) with micro- and nanorods and nanospheres morphology were prepared via sonochemical route under ultrasonic irradiation without any surfactants at room temperature. These new micro and nano-structures were characterized by different techniques. To examine the effect of synthesis method on the porosity of the frameworks N2 adsorption (BET analysis) was applied. The influence of sonication time and various concentrations of initial reagent on the morphology and size of the F-MOFs nanostructures were investigated. The results indicated that by increasing the time of ultrasonic radiation and concentration, smaller nanostructures form and morphological changes occurred. These two frameworks with the presence of hydrophobic fluoro groups near the basic reaction center in the F-MOFs are interesting candidates as an efficient catalyst in the Henry reaction for a comparative catalytic study. This investigation indicates the important role of the F-MOFs nanostructures synthesized by the ultrasonic method with the high surface area as heterogeneous catalysts with remarkable catalytic activity compared with other MOFs.

Water-stable fluorinated metal–organic frameworks (F-MOFs) with hydrophobic properties as efficient and highly active heterogeneous catalysts in aqueous solution

Two new fluorinated MOFs were synthesized, characterized and used as heterogeneous catalysts toward the Knoevenagel condensation reaction.

Syntheses, Crystal Structures and Luminescent Properties of Two Isostructural Fluorinated Metal–organic Frameworks Based on Mixed 2,3,5,6-tetrafluoro-1,4-bis(imidazole-1-yl-methyl)Benzene and Oxalate Ligands

Two isostructural fluorinated metal-organic frameworks [M(Fbix)(ox)]n (where M = Zn or Mn, Fbix = 2,3,5,6-tetrafluoro-1,4-bis(imidazole-1-yl-methyl)benzene, ox = oxalate) have been synthesised from Fbix and oxamide under hydrothermal conditions, where oxalate is generated by the in situ hydrolysation of oxamide. The complexes are isostructural and display similar two-dimensional undulating sql nets formed by pillaring the one-dimensional [M(ox)]n chains through Fbix linkers. Their solid-state fluorescence spectra indicate a ligand-based emission for both complexes.

Functionalization and Isoreticulation in a Series of Metal-Organic Frameworks Derived from Pyridinecarboxylates.

The partially fluorinated metal-organic frameworks (F-MOFs) have been constructed from 3-fluoro-4-pyridinecarboxylic acid and trans-3-fluoro-4-pyridineacrylic acid linkers using Mn(2+), Co(2+), and Cd(2+) metals via the solvothermal method, which show isostructural isomerism with their nonfluorinated counterparts synthesized using 4-pyridinecarboxylic acid and trans-4-pyridineacrylic acid, respectively. The simultaneous effect of partial fluorination and isoreticulation on structure and H2 adsorption has been studied systematically in isostructural nonfluorinated and partially fluorinated MOFs, which shows that the increment in the hydrogen uptake properties in F-MOFs is not a universal phenomenon but is rather system-specific and changes from one system to another.

Mesoporous Fluorinated Metal–Organic Frameworks with Exceptional Adsorption of Fluorocarbons and CFCs

AbstractTwo mesoporous fluorinated metal–organic frameworks (MOFs) were synthesized from extensively fluorinated tritopic carboxylate‐ and tetrazolate‐based ligands. The tetrazolate‐based framework MOFF‐5 has an accessible surface area of 2445 m2 g−1, the highest among fluorinated MOFs. Crystals of MOFF‐5 adsorb hydrocarbons, fluorocarbons, and chlorofluorocarbons (CFCs)—the latter two being ozone‐depleting substances and potent greenhouse species—with weight capacities of up to 225 %. The material exhibits an apparent preference for the adsorption of non‐spherical molecules, binding unusually low amounts of both tetrafluoromethane and sulfur hexafluoride.

Mesoporous Fluorinated Metal-Organic Frameworks with Exceptional Adsorption of Fluorocarbons and CFCs.

Two mesoporous fluorinated metal-organic frameworks (MOFs) were synthesized from extensively fluorinated tritopic carboxylate- and tetrazolate-based ligands. The tetrazolate-based framework MOFF-5 has an accessible surface area of 2445 m(2) g(-1), the highest among fluorinated MOFs. Crystals of MOFF-5 adsorb hydrocarbons, fluorocarbons, and chlorofluorocarbons (CFCs)-the latter two being ozone-depleting substances and potent greenhouse species-with weight capacities of up to 225%. The material exhibits an apparent preference for the adsorption of non-spherical molecules, binding unusually low amounts of both tetrafluoromethane and sulfur hexafluoride.