Microporous MOF Research Articles

Electrochemical Sensitization of Activated Carbon by Microporous MOF for Supercapacitor Applications

AbstractThe remarkable performance of activated carbon as active electrode material in supercapacitors enabled its large‐scale industrialization. Herein, the utilization of facile physical mixing process of microporous, chemically robust, Zr‐based metal‐organic framework for surface‐modification of activated carbon to enhance its charge retention capacitance is reported. In this approach, the high surface area of the microporous MOF increases the active surface area of the activated carbon, providing an extra layer with facilitated electrolyte diffusion properties that effectively modulates the solid–electrolyte interface. A critical optimal coverage of 5wt % by the MOF crystallites is identified, resulting in increased specific capacitance of the activated carbon by ∼80 %, as compared to the pristine carbon. At higher MOF coverage, the poor electronic conductivity of the MOF hindered the inter‐grain charge mobilization within the activated carbon, thus adversely affecting the overall capacitive performance.

Microporous MOF as nanogen facilitating diffusion-coupled charge transfer near the percolation threshold in a polyaniline pseudo-supercapacitor

A facile and potentially transferrable approach to enhance the PANI specific capacitance through the incorporation of MOF nanocrystals, as a microporous filler (nanogens), into the PANI matrix to provide ion-diffusion channels within the matrix.

Spatial disposition of square-planar mononuclear nodes in metal-organic frameworks for C2H2/CO2 separation.

The efficient separation of acetylene (C2H2) from its mixture with carbon dioxide (CO2) remains a challenging industrial process due to their close molecular sizes/shapes and similar physical properties. Herein, we report a microporous metal-organic framework (JNU-4) with square-planar mononuclear copper(ii) centers as nodes and tetrahedral organic linkers as spacers, allowing for two accessible binding sites per metal center for C2H2 molecules. Consequently, JNU-4 exhibits excellent C2H2 adsorption capacity, particularly at 298 K and 0.5 bar (200 cm3 g-1). Detailed computational studies confirm that C2H2 molecules are indeed predominantly located in close proximity to the square-planar copper centers on both sides. Breakthrough experiments demonstrate that JNU-4 is capable of efficiently separating C2H2 from a 50 : 50 C2H2/CO2 mixture over a broad range of flow rates, affording by far the largest C2H2 capture capacity (160 cm3 g-1) and fuel-grade C2H2 production (105 cm3 g-1, ≥98% purity) upon desorption. Simply by maximizing accessible open metal sites on mononuclear metal centers, this work presents a promising strategy to improve the C2H2 adsorption capacity and address the challenging C2H2/CO2 separation.

High CO2 separation performance on a metal–organic framework composed of nano-cages lined with an ultra-high density of dual-side open metal sites

High CO2 separation performance on a microporous MOF incorporting nano-cages and an ultra-high density of dual-side open metal sites is reported.

An anthracene-based microporous metal–organic framework for adsorbing CO2 and detecting TNP sensitivity

An anthracene-based microporous MOF of CUST-607 was synthesized by a solvothermal method. CUST-607 possesses a large surface area and shows strong adsorption toward CO2. In the fluorescence experiments, CUST-607 exhibits total quenching for TNP.

A microporous calcium-based MOF for separation of CH4 from C2 hydrocarbons and CO2

A hms-type microporous metal-organic framework, {[Ca3(NTB)2(H2O)2]·NMF·4NMP·4H2O}n (Ca-MOF, H3NTB = 4,4′,4″-nitrilotrisbenzoic acid, NMF = N-methyl formamide, NMP = N-methyl-2-pyrrolidone), was solvothermal synthesized. Desolvated Ca-MOF shows relatively high C2 hydrocarbons and CO2 storage capacity at 298 K and 1 atm (C2H2: 107.0 cm3 g−1, C2H4: 79.0 cm3 g−1, C2H6: 99.2 cm3 g−1, CO2: 65.9 cm3 g−1), and a lower CH4 adsorption uptake (14.6 cm3 g−1). Its ideal adsorbed solution theory (IAST)-predicted selectivities of C2 hydrocarbons and CO2 over CH4 range from 5.7 to 10.0 at room temperature, indicating its potential for separation of C2 hydrocarbons and CO2 from CH4.

Confining CsPbX3 perovskites in a hierarchically porous MOF as efficient and stable phosphors for white LED

Confining metal-halide perovskites within MOF hosts not only protects them from exterior environment stimulation and isolates them from each other without aggregation, but also enables a variety of new features and applications. In this work, a hierarchically porous MOF host was firstly explored for in-situ confined growth of CsPbX3 perovskite nanocrystallites (PNCs). Compared with the previously used microporous MOF matrixes, this hierarchically porous MOF not only enables the impregnation of perovskite precursors in one step, but also allows more facile diffusion of the reactants, thus giving rise to high loading capacities and uniform distribution of CsPbX3 perovskites. The MOF matrix serves as both template to guide the confined growth of monodispersed CsPbX3 PNCs and encapsulation to enhance the stability of CsPbX3 PNCs. The obtained CsPbX3@MOF nanocomposites show bright luminescence and good resistance to ambient moisture, UV light irradiation, and anion-exchange. By integrating the green-emitting CsPbBr2I@MOF and red-emitting CsPbI3@MOF nanocomposites with a commercial blue InGaN LED chip, we fabricate a primary WLED showing a NTSC value of 125% and Rec. 2020 of 93%, which highlights the potential in backlight display.

Molecular Surgery at Microporous MOF for Mesopore Generation and Renovation

AbstractHierarchically porous MOFs (HP‐MOFs) present advantageous synergism of micro‐ and mesopore but challenging in synthetic control at molecular scale. Herein, we present the first example of reversible and controllable mesopore generation and renovation in a microporous MOF of HKUST‐1 via synthetic manipulation at molecular scale. An ammonia‐gas etching strategy is proposed to create mesopores in carboxylate‐based microporous MOFs and thus produce HP‐MOFs. Gas‐phase etching ensures uniform mesopore formation inside the MOF crystals via plane‐oriented cutting the carboxylate‐metal bonds off without affecting the crystal size and morphology. The mesopore size is controlled by the etching temperature, while the mesopore volume could be tuned by adjusting etchant pressure. The generated mesopores could be renovated using MOF precursors solutions so that to achieve controllable mesopore generation/closure, and encapsulation of the adsorbed molecules. This work demonstrates a powerful protocol for precisely tailoring and tuning the properties of MOF materials at molecular scale.

Molecular Surgery at Microporous MOF for Mesopore Generation and Renovation.

Hierarchically porous MOFs (HP-MOFs) present advantageous synergism of micro- and mesopore but challenging in synthetic control at molecular scale. Herein, we present the first example of reversible and controllable mesopore generation and renovation in a microporous MOF of HKUST-1 via synthetic manipulation at molecular scale. An ammonia-gas etching strategy is proposed to create mesopores in carboxylate-based microporous MOFs and thus produce HP-MOFs. Gas-phase etching ensures uniform mesopore formation inside the MOF crystals via plane-oriented cutting the carboxylate-metal bonds off without affecting the crystal size and morphology. The mesopore size is controlled by the etching temperature, while the mesopore volume could be tuned by adjusting etchant pressure. The generated mesopores could be renovated using MOF precursors solutions so that to achieve controllable mesopore generation/closure, and encapsulation of the adsorbed molecules. This work demonstrates a powerful protocol for precisely tailoring and tuning the properties of MOF materials at molecular scale.

Hierarchical mesoporous zinc-imidazole dicarboxylic acid MOFs: Surfactant-directed synthesis, pH-responsive degradation, and drug delivery

The surfactant template-directed solvothermal method was applied in the synthesis of hierarchical mesoporous zinc-imidazolate derivative metal–organic framework (mesoMOF), which was then utilized for active loading of cisplatin (cis-Pt). To fabricate mesoMOF, various amounts of the surfactant (cetyltrimethylammonium bromide: 0.1–0.3 g) and linker (citric acid: 0.05–0.15 g) were added to the reaction mixture, which resulted in different particle sizes and morphologies. MesoMOF quality attributes such as Specific surface area (SSA), total porous volume, and Barrett-Joyner-Halenda (BJH) pore diameter were also determined. At the optimum reaction condition, mesoMOF with a high surface area (1859 m2/g), pore diameter (14.13 nm) and total pore volume (0.314 cm3/g) was attained. In the next step, cis-Pt was actively loaded in the mesoMOF with a high loading capacity (28% w/w), which was remarkably superior to the microporous MOF. Interestingly, in mildly acidic pH (5.5), mesoMOF underwent degradation, resulting in a rapid release of cis-Pt. Cell viability and apoptosis induction assays confirmed the superiority of the cis-Pt loaded mesoMOF over free drug in a resistant ovarian tumor cell line (A2780cp). Altogether, due to their tunable size and morphology, pH-responsiveness, and acceptable tolerability in mice, the mesoMOFs can be regarded as an anti-cancer drug delivery system.

Deciphering the Supramolecular Organization of Multiple Guests Inside a Microporous MOF to Understand their Release Profile

AbstractMetal‐organic frameworks (MOFs) give the opportunity of confining guest molecules into their pores even by a post‐synthetic protocol. PUM168 is a Zn‐based MOF characterized by microporous cavities that allows the encapsulation of a significant number of guest molecules. The pores engineered with different binding sites show a remarkable guest affinity towards a series of natural essential oils components, such as eugenol, thymol and carvacrol, relevant for environmental applications. Exploiting single crystal X‐ray diffraction, it was possible to step‐wisely monitor the rather complex three‐components guest exchange process involving dimethylformamide (DMF, the pristine solvent) and binary mixtures of the flavoring agents. A picture of the structural evolution of the DMF‐to‐guest replacement occurring inside the MOF crystal was reached by a detailed single‐crystal‐to‐single‐crystal monitoring. The relation of the supramolecular arrangement in the pores with selective guests release was then investigated as a function of time and temperature by static headspace GC‐MS analysis.

Electronic tuning of confined sub-nanometer cobalt oxide clusters boosting oxygen catalysis and rechargeable Zn–air batteries

Reasonable design of robust bifunctional oxygen catalysts from an electronic structure perspective is intriguing and challenging for the development of high active rechargeable zinc-air batteries (ZABs). In this study, the favorable regulation of the electronic structure of the cobalt oxide nanoclusters was firstly predicted by density functional theory (DFT) simulation, and then experimentally verified by confining sub-nanometer CoO x clusters (0.86 nm) into the small pore of ZIF-8 derived N-doped nanomaterials (PNC) using a microporous MOFs confinement strategy. The confined effect of the MOF micropores not only enhanced the stability of the sub-nanometer cobalt oxide clusters, but also make it coupled with Co‒N x to further regulate the electronic structure of the former, synergistic resulting in enhanced ORR/OER actives. As a result, the optimized 0.05CoO x @PNC catalyst demonstrates outstanding bifunctional oxygen performance with a smaller potential gap of 0.67 V. Moreover, the rechargeable Zn-air batteries integrated 0.05CoO x @PNC air cathode displays encouraging performance with a peak power density of 157.1 mW cm −2 , a specific capacity of 887 mAh g Zn −1 at 10 mA cm −2 and long-term cyclability for over 200 h, significantly outperforming the benchmark electrode couple consisted of Pt/C/RuO 2 . DFT calculation further revealed that reducing particle size and coupling with Co‒N could effectively regulate the charge distribution of CoO x nanoclusters and downshift the d -band center of Co adsorption sites in CoO x nanoclusters, which reduced the reaction barrier of intermediate O 2 * and OH* and ORR/OER overpotential, thus accelerating the overall ORR/OER kinetic process. This work offers a novel reference for the construction of a robust sub-nanometer cluster catalysts in the field of ZABs. The ultra-stable sub-nanometer CoO x clusters/Co, N co-doped porous carbon as bifunctional oxygen catalyst by a microporous MOF confinement strategy. ● An ultra-stable CoO x nanoclusters catalyst were synthesized by a microporous MOF confinement strategy. ● Coupling with Co-N x can further regulate to the electronic structure of the confined CoO x nanoclusters. ● Reducing particle size and coupling with Co-N could effectively reduce the reaction barrier of O 2 * and OH*. ● The catalyst exhibits excellent bifunctional catalytic activities and stable rechargeability of zinc-air battery.

A microporous Ce-based MOF with the octahedron cage for highly selective adsorption towards xenon over krypton.

The collection of high-purity noble gases with recyclable nuclides provides substantial economic benefits and minimizes the risk of environmental pollution, which is a future development tendency for nuclear industries. Here, Ce-SINAP-1, with its radiation-resistance (up to 20 kGy of γ-ray irradiation) and suitable pore channels for the separation of noble gases (Ar, Kr and Xe), was synthesized. Ce-SINAP-1 exhibited the selective adsorption of Xe (2.02 mmol g−1) over Kr (0.67 mmol g−1) and Ar (0.27 mmol g−1) at 293 K (1 bar) with a Henry's selectivity of 8.24 (Xe/Kr), and an ideal adsorbed solution theory selectivity of 14.9 (Xe : Kr 20 : 80). The result of the dynamic breakthrough experiment also indicates a good separation for Xe/Kr with Ar.

A new 2D lanthanum based microporous MOF for efficient synthesis of cyclic carbonates through CO2 fixation

We report a new microporous La-MOF La-5-SIP-MOF through solvothermal reaction and it showed high catalytic activity for the synthesis of cyclic carbonates from epoxides via the CO2 fixation reaction at room temperature.

Fast multipoint immobilization of lipase through chiral L-proline on a MOF as a chiral bioreactor.

In this paper, we describe the facile preparation of a chiral catalyst by the combination of the amino acid, l-proline (Pro), and the enzyme, porcine pancreas lipase (PPL), immobilized on a microporous metal-organic framework (PPL-Pro@MOF). The multipoint immobilization of PPL onto the MOF is made possible with the aid of Pro, which also provided a chiral environment for enhanced enantioselectivity. The application of the microporous MOF is pivotal in maintaining the catalytic activity of PPL, wherein it prevented the leaching of Pro during the catalytic reaction, leading to the enhanced activity of PPL. The prepared biocatalyst was applied in asymmetric carbon-carbon bond formation, demonstrating the potential of this simple approach for chemical transformations.

Iron-doping on Cu–N–C composite with enhanced CO faraday efficiency for the electrochemical reduction of CO2

Fe–N–macrocycles have been viewing as the most promising catalyst for CO2ER. It is of great importance to explore the performance of composite CuFe–N–C in CO2ER. Fe-Cu–BTT precursor was prepared by introducing the ferrous ion to a microporous N-rich MOF. It exhibits a lower plateau temperature of 800 ℃ than the prototype. The pyrolysis product of FexCu–N–C increases the selectivity of CO2-to−CO due to the increase of the BET surface area, the total pore volume, and the Fe–Nx sites, as well as a lower density of Cu NPs in the carbon matrix. The Fe0.07Cu–N–C800 exhibits the highest FECO of 48.5 %.

Kinetic separation of C4 olefins using Y-fum-fcu-MOF with ultra-fine-tuned aperture size

The separation of C4 olefin mixtures into pure components is one of the most challenging processes in chemical industries. Adsorption-based separation, using ultra-microporous materials, is considered as a viable alternative to reduce the operating cost of the currently employed but energy intensive distillation technique. The understanding of structural properties-relationships for C4 olefins separation using solid state materials is still lacking particularly for microporous materials with purely cage-based structures. Herein, the adsorptive separation of C4 olefins (butene isomers and 1,3-butadiene) by the microporous MOF, Y-fum-fcu-MOF, containing octahedral and tetrahedral cages with triangular pore aperture size (≈4.7 Å), is studied. The adsorption capacities of the MOF for C4 olefins were assessed by measuring the single component adsorption isotherms at 30 °C which led to very similar equilibrium adsorption uptakes at saturation for the components (excluding isobutylene). However, adsorption breakthrough curves collected at 25 °C and Pulse Gas Chromatography experiments, conducted to define the guest–host affinity at very low concentration (Henry’s region), evidenced kinetically driven separation of C4 olefins by Y-fum-fcu-MOF. In fact, a strong relation between pores window size, kinetic diameter of the components and their adsorption behavior was observed. The breakthrough capacity decreases at increasing molecular size, allowing the separation of cis- and trans-2-butene despite the quite similar adsorption enthalpies for these components (42.0 and 37.7 kJ/mol, respectively).

A unique 3D microporous MOF constructed by cross-linking 1D coordination polymer chains for effectively selective separation of CO2/CH4 and C2H2/CH4

Selective separation of CO2/CH4 and C2H2/CH4 are promising for their high-purity industrial demand and scientific research on account of the similar molecular radius and physical properties. In this work, a unique 3D microporous MOF material [Cu(SiF6)(sdi)2]·solvents (1, sdi = 1,1′-sulfonyldiimidazole) was successfully constructed by cross-linking 1D coordination polymer chains. The dense functional active sites on the inner walls of the channel of 1a can provide strong binding affinities to CO2, C2H2, and thus effectively improve the gas separation performance of CO2/CH4 and C2H2/CH4.

A Microporous MOF with Inorganic Nitrate Ions Immobilized on a Porous Surface Displaying Efficient C2H2 Separation and Purification

A microporous MOF based on a heterotopic ligand was successfully synthesized under solvothermal conditions and fully characterized using single‐crystal and powder X‐ray diffraction, TGA, FTIR, and microanalyses. Single‐crystal X‐ray diffraction analyses showed that the title MOF contains rich inorganic nitrate ions decorating the channel surface that can serve as C2H2 recognition sites. Its selective gas adsorption properties towards C2H2 over CO2 and CH4 were evaluated by single‐component equilibrium adsorption measurements and IAST calculations, establishing its promising potential for C2H2 separation and purification. At ambient conditions, the C2H2 uptake capacity reaches 92.2 cm3 (STP) g–1, while the IAST‐predicted adsorption selectivities are up to 30.6 and 4.5 for the equimolar C2H2‐CH4 and C2H2‐CO2 binary gas mixtures, respectively. Furthermore, DFT computation studies revealed that the inorganic nitrate ion plays a very important role for preferential adsorption of C2H2 over CO2 and CH4.

Porphyrinic zirconium-based MOF with exposed pyrrole Lewis base site as an efficient fluorescence sensing for Hg2+ ions, DMF small molecule, and adsorption of Hg2+ ions from water solution

The microporous zirconium-based MOF, as known [PCN-221], was successfully prepared by the solvothermal reaction method using meso-tetra(4-carboxyphenyl) porphyrin (TCPP) as a ligand and used as a fluorescent sensor for sensitive and selective recognition of Hg2+ ions, DMF small molecule, and adsorption of Hg2+ ions. The sensing of [PCN-221] showed a quenching response of Hg2+ ions with a fast fluorescent response rate under <1 ​min. The fluorescence quenching constant is calculated to be 4021.9 ​M-1 by linear correlation for Hg2+ ions in a low concentration range from 0 to 300 ​μM, also the detection limit was calculated to be 0.01 ​μM. Moreover, the prepared [PCN-221] can perform as a fluorescence turn-off sensor for highly sensitive detection of DMF in methanol solution at the line range of 50–1000 ​μM and, the quenching constant is calculated to be 28.231 ​M-1 by the experiment fluorescence titration for a DMF in low concentration, also the detection limit was calculated to be 0.12 ​μM. As well as, the [PCN-221] exhibited a high adsorption of Hg2+ ions in water solution between hazardous heavy metals and compare to other MOFs reported to date. The Hg2+ adsorption process follows pseudo-second-order kinetics, removing 95% of the metals in 30 ​min. Totally, the UV–Vis study provides insight to assist realized the interaction mechanism between [PCN-221] and Hg2+ ions.