Cationic Metal-organic Framework Research Articles

Cationic Metal–Organic Framework with Amino-Functionalized Isonicotinic Acid for Chromium(VI) Removal

Cationic Metal–Organic Framework with Amino-Functionalized Isonicotinic Acid for Chromium(VI) Removal

CTAB modified metakaolin-based geopolymer microspheres for the selective adsorption and recovery of TcO4−/ReO4−

With the increase of radioactive wastewater, it is a major challenge to efficient removal of TcO4− from radioactive wastewater. So far, cationic metal organic frameworks (MOFs), cationic covalent organic frameworks (COFs), cationic polymeric networks (CPNs) and porous organic polymer materials (POPs) can remove TcO4− efficiently, but the cumbersome preparation process and high cost limit their practical applications. Herein, an efficient and low-cost CTAB-modified metakaolin-based geopolymer microspheres (CTAB@MGMs) with excellent adsorption properties for ReO4− is simply and rapidly synthesized by dispersion-pelletizing-solidification and vacuum infusion methods. CTAB@MGMs has fast adsorption kinetics (equilibrium in 10 min), a wide pH application range (2–10) and high selectivity in competing ions (PO43−, SO42−, NO3−, Cl−) and real waters (tap water, surface water, seawater). Importantly, complete desorption of the adsorbed sample can be realized by ethanol and MGMs can be recycled without performance decay. Meanwhile, ethanol recycling was achieved by spin-evaporation of desorption solution and a novel compound CTA-ReO4 was generated. We have analyzed and reported the crystal structure of CTA-ReO4 (CCDC Numbers: 2282273) for the first time and revealed the mechanism that ReO4− is removed by electrostatic and coordination synergism with quaternary ammonium salts after ion exchange. CTAB@MGMs is a low-cost, novel and reusable adsorbent with potential use for the removal of TcO4− from radioactive wastewater.

Reticular access to triptycene-based cationic metal–organic frameworks for protein-bound uremic toxins sorption

P-cresyl sulfate (pCS) and indoxyl sulfate (IS), a class of protein-bound uremic toxins, cannot be effectively cleared through hemodialysis treatment due to their strong binding to human serum albumin, posing a potential risk of cardiovascular disease in patients with chronic renal failure. Herein, we designed and prepared novel cationic metal–organic frameworks (MOFs), denoted as ZJU-X18, for the efficient removal of pCS and IS. A triptycene-based rigid trigonal prismatic ligand was utilized to link with Ag+ to yield a rare 4-fold interpenetrated MOF with abundant hydrophobic channels, affording high sorption capacity, excellent selectivity, and decent recyclability toward uremic toxins. Furthermore, the anion-exchange process between ZJU-X18 and uremic toxins is verified through density functional theory (DFT) calculations. This study provides a proactive example of the rational design of cationic MOFs from the perspective of reticular chemistry and demonstrates their promising application in uremia treatment.

Tunable Gas Admission via a "Molecular Trapdoor" Mechanism in a Flexible Cationic Metal-Organic Framework Featuring 1D Channels.

Achieving high gas selectivity is challenging when dealing with gas pairs of similar size and physiochemical properties. The "molecular trapdoor" mechanism discovered in zeolites holds promise for highly selective gas adsorption separation but faces limitations like constrained pore volume and slow adsorption kinetics. To address these challenges, for the first time, a flexible metal-organic framework (MOF) featuring 1D channels and functioning as a "molecular trapdoor" material is intoduced. Extra-framework anions act as "gate-keeping" groups at the narrowest points of channels, permitting gas admissions via gate opening induced by thermal/pressure stimuli and guest interactions. Different guest molecules induce varied energy barriers for anion movement, enabling gas separation based on distinct threshold temperatures for gas admission. The flexible framework of Pytpy MOFs, featuring swelling structure with rotatable pyridine rings, facilitates faster gas adsorption than zeolite. Analyzing anion properties of Pytpy MOFs reveals a guiding principle for selecting anions to tailor threshold gas admission. This study not only overcomes the kinetic limitations related to gas admission in the "molecular trapdoor" zeolites but also underscores the potential of developing MOFs as molecular trapdoor adsorbents, providing valuable insights for designing ionic MOFs tailored to diverse gas separation applications.

Preferential separation of a radioactive TcO4- surrogate from a mixture of oxoanions by a cationic MOF.

Preferential trapping of a selected metal-oxoanion from a mixture of other metal-oxoanionic toxic pollutants in water has been demonstrated by implementing energy-efficient adsorption followed by the ion-exchange method, utilizing a hydrolytically stable cationic metal-organic framework (MOF). The cationic MOF exhibits ultrafast and selective extraction efficiency towards ReO4- (a surrogate anion of radioactive TcO4-) over other metal-oxoanions in contaminated water systems.

High-Performance enrichment and sensitive analysis of bisphenol and its analogues in water and milk using a novel Ni-Based cationic Metal-Organic framework

A novel cationic metal–organic framework (iMOF-Ni) was designed and synthesized by a solvothermal method. It was fabricated as a solid-phase extraction (SPE) cartridge and exhibited high adsorption performance for Bisphenols (BPs). The theoretical simulation demonstrated that the adsorption mechanism between iMOF-Ni and BPs was attributed to cation-π bonding, π-π interaction, and electrostatic interactions. Under optimized SPE, a method for analyzing BPs was established by combining high-performance liquid chromatography-diode array detection (HPLC-DAD). The developed method has good linearity (R2 ≥ 0.994), low detection limits (0.07–0.16 ng/mL), and good reproducibility (1.72–6.35 %, n = 6). The applicability of the method was further evaluated by analyzing water and milk samples. Recoveries of four BPs in spiked samples were from 72.2 % to 96.6 %.

Synergistic Induction of Solvent and Ligand-Substitution in Single-Crystal to Single-Crystal Transformations toward a MOF with Photocatalytic Dye Degradation.

External-stimuli responsiveness as found in natural organisms and smart materials is attractive for functional materials scientists who attempt to design and imitate fascinating behavior into their materials. Herein, we report a couple of new solvent-responsive isostructural two-dimensional cationic metal-organic frameworks (MOFs) of Mn(II) (1a) and Zn(II) (2a) that undergo unprecedented single-crystal to single-crystal (SCSC) transformation toward the corresponding isostructural three-dimensional MOFs of Mn(II) (1b) and Zn(II) (2b). The 2D MOFs 1a and 2a have been effortlessly and rapidly synthesized via the microwave-heating technique. The SCSC transformations are synergistically induced by solvent and ligand-substitution reactions and able to be triggered by water, methanol, ethanol, and n-propanol. Time-dependent SCSC transformations were studied by in situ X-ray diffraction. Investigations on photodegradation of methyl orange showed that Zn-MOF 2b has higher efficiency than Mn-MOF 1b under UV-C irradiation at 300 min, 94.27%, and 21.91%, respectively. The influence of charge on the dye molecules, heterogeneity of the catalysis, and •OH radical-scavenging test was studied. First-principles computations suggest that the high photocatalytic activity of 2b may be attributed to its suitable band-edge position for redox reactions.

Construction of efficient ion transport channels in MOFs-blended poly (ether ether ketone) containing multiple ion transport sites

In this paper, trimethyl poly (ether ether ketone) (T-PEEK) containing multiple sites was prepared by a polycondensation reaction, and afterwards, brominated T-PEEK (Br-T-PEEK) and imidazole functionalized T-PEEK (Im-T-PEEK) were prepared by substitution reaction. And cationic metal organic frameworks UiO-66-NH2 (C-MOF) was synthesized as fillers. Composite membranes were fabricated by incorporating cationic UiO-66-NH2 into imidazole functionalized Im-T-PEEK. Im-T-PEEK/C-MOF-5% (the weight percentage of C-MOF was 5%) composite membranes exhibit good mechanical properties, such as Young's modulus of 2319.06 MPa and tensile strength of 38.34 MPa. The ionic conductivity of the composite membrane, Im-T-PEEK/C-MOF-5%, achieved a remarkable value of 106.4 mS cm−1 at a temperature of 80 °C. All the membranes exhibited good alkaline stability. After immersing the prepared membranes in a solution of 1 M NaOH at a temperature of 60°C for a duration of 360 h, it was observed that the ionic conductivity of the membranes retained more than 70% of their initial ionic conductivity. Furthermore, the open-circuit voltage and peak power density of Im-T-PEEK/C-MOF-5% reached 0.904 V and 154.26 mW cm−2, respectively. In a word, this study presents a promising strategy for the preparation of advanced anion exchange membranes (AEMs) with good properties for energy conversion and storage applications.

Nitrogen-doped carbon-encompassed Ni nanoparticles prepared from Ni (II) cation-exchanged metal organic framework for efficient electrochemical CO2 reduction

Carbon layer-encompassed nickel nanoparticles of core–shell structure (designated as Ni NPs@NC) show notable advantages toward electrochemical carbon dioxide reduction reaction (CO2RR). Core-shell structured Ni NPs@NC nanoparticles anchored on the carbon matrix have been conveniently built from a cationic metal–organic framework (CPM-72 herein) which incorporates the Ni2+ cations through the cation exchange before high-temperature pyrolysis. The designed Ni NPs@NC catalyst exhibited impressive CO2RR performance which could efficiently convert CO2 into CO (carbon monoxide). In the H-type cell, a maximal CO faradaic efficiency (FE) of 86.4% was achieved at −0.8 V (vs. RHE) with a high CO partial current density (jco) of −11.0 mA cm−2. In the flow cell device, the CO FE was further improved to 98.6% with the enhanced jco of −38.7 mA cm−2. Finally, Zn-CO2 battery test also delivered a peak power density of 0.39 mW cm−2 at 2.65 mA cm−2.

A robust ultra-microporous cationic aluminum-based metal-organic framework with a flexible tetra-carboxylate linker

Al-based cationic metal-organic frameworks (MOFs) are uncommon. Here, we report a cationic Al-MOF, MIP-213(Al) ([Al18(μ2-OH)24(OH2)12(mdip)6]6Cl·6H2O) constructed from flexible tetra-carboxylate ligand (5,5'-Methylenediisophthalic acid; H4mdip). Its crystal structure was determined by the combination of three-dimensional electron diffraction (3DED) and high-resolution powder X-ray diffraction. The structure is built from infinite corner-sharing chains of AlO4(OH)2 and AlO2(OH)3(H2O) octahedra forming an 18-membered rings honeycomb lattice, similar to that of MIL-96(Al), a scarce Al-polycarboxylate defective MOF. Despite sharing these structural similarities, MIP-213(Al), unlike MIL-96(Al), lacks the isolated μ3-oxo-bridged Al-clusters. This leads to an ordered defective cationic framework whose charge is balanced by Cl- sandwiched between two Al-trimers at the corner of the honeycomb, showing strong interaction with terminal H2O coordinated to the Al-trimers. The overall structure is endowed by a narrow quasi-1D channel of dimension ~4.7 Å. The Cl- in the framework restrains the accessibility of the channels, while the MOF selectively adsorbs CO2 over N2 and possesses high hydrolytic stability.

Isoelectric Substitution Strategy to Construct a Partially Charged MOF for C2H2 Capture and Selective Dye Adsorption

The charged metal–organic framework (MOF) (anionic and cationic MOF) material plays an important role in gas adsorption and separation and ecological environment management. Herein, we reported a partially charged Mg-based MOF (FJU-129) with dimethylamine counterions, which can efficiently separate C2H2 from CO2 and rapidly adsorb the cationic dye methylene blue (MB). FJU-129a showed a high uptake capacity of up to 133.8 cm3/g for C2H2 at 273 K, 1 bar, and low isosteric heat of adsorption of C2H2 (24.78 kJ/mol). The C2H2/CO2 separation is validated by a dynamic breakthrough experiment at 296 K, 1.5 bar, and the Grand Canonical Monte Carlo simulation revealed that the partially remaining charge on the magnesium sites has an electrostatic force on the −C≡C– bond of C2H2 molecules, and C–H···π interactions play an important role in the separation of C2H2/CO2 selective mixtures. In addition, owing to the pore size and electrostatic effect, FJU-129 selectively absorbs MB and excludes other cationic dyes and anionic dyes (MB, CV, RB, R6G, MO, and SD-III).

Structural flexibility in cationic metal–organic framework for boosting ReO4− capture

ReO4−, as a typical anion, its capture is now receiving increasing attentions. However, there still lacks effective method to boost the uptake performance of materials, except for designing new materials. In this work, we found that the structural flexibility could be a good candidate to boost ReO4− uptake. The used flexible cationic MOF, [Co(H2O)2(TIB)][NO3]2 (named as Co-TIB-NO3, TIB = 3,3′,5,5′-tetra(1H-imidazol-1-yl)-1,1′-biphenyl), showed a multiple response towards temperature, counterion, and solvents with the observation of three different structures, including crystalline OP (open pore) phase, crystalline CP (closed pore) phase, and amorphous CP phase. The origin of the structural flexibility is quite complicated, involving a cage-to-channel migration for counterion, interlayer compression, and deformation of organic ligands. The developed material, Co-TIB-NO3-313, showing the amorphous CP phase, was found to perform outstanding ReO4− capture with a high uptake capacity, rapid adsorption rate, large distribution coefficient, excellent selectivity, and recyclability, suggesting its superior application in ReO4− capture.

Anion−π Interaction Powered Perrhenate Recognition and Extraction in Aqueous Media

Selective anion recognition and extraction in aqueous media is a challenging research topic, and the anion-π interaction is an undetermined solution for the development of anion sorbent materials with better affinity and selectivity. Here, noncovalent anion-π interaction was introduced as the driving force for this purpose. A cage-based 2D cationic metal-organic framework, IPM-21, is featured with porous channels formed by complementary V-shape electron-deficient cavities. This 3D rhombic electron-deficient cavity can bind two anions with the clipped π-acidic surfaces, exhibiting much higher affinity toward ReO4- due to the strong complementary effect. This cavity was forced to expand its opening size to seamlessly adopt the ReO4- anion with a large volume. Experimental results found that the binding energy of IPM-21 with ReO4- is around 2.3 kJ/mol higher than that with ClO4-. Parts per million levels of the ReO4- anion in aqueous media can be effectively extracted by IPM-21 with a removal up to 99%, even with mixed competing anions. IPM-21 can be easily recycled and reused by treatment with high concentration aqueous NaClO4. Due to the extremely low interlamellar interaction, the IPM-21 crystal exhibited enhanced ReO4- extraction performance with the recycling times due to self-exfoliation; as a result, ultrathin IPM-21 nanosheets with large lateral sizes were produced in this process.

Fluorescence sensing platform for Cronobacter sakazakii based on the cationic metal-organic frameworks modified upconversion nanoparticles

Cronobacter sakazakii ( C. sakazakii ) is a serious threat to human health. Efficient detection of C. sakazakii is crucial for food safety and the control of foodborne diseases. Here, a fluorescence sensing platform for C. sakazakii was constructed with α-glucosidase and cationic metal-organic framework-functionalized upconversion nanoparticles (UCNPs@MOFs). The anionic α-glucosidase was inhibited by binding to cationic UCNPs@MOFs. The presence of C. sakazakii competitively combined with cationic UCNPs@MOFs and released α-glucosidase into the enzyme substrate solution (para-nitrophenyl-α- d -glucopyranoside) to recover activity, thus triggering fluorescence quenching of cationic UCNPs@MOFs through the product of 4-nitrophenol. In addition, α-glucosidase from C. sakazakii accelerated the formation of 4-nitrophenol, thus improving the fluorescence response of cationic UCNPs@MOFs. This strategy illustrates high sensitivity of the designed platform for C. sakazakii with a wide linear range (1.1×10 2 –1.1 × 10 8 cfu mL −1 ), a low limit of detection (3.2 × 10 1 cfu mL −1 ), and an acceptable recovery value (85.2–111.5%) in real samples (tap water, infant formula powder, and goat milk powder). These results confirm that the proposed fluorescence platform is an ideal candidate tool for the detection of C. sakazakii in microbiological diagnostics. • A highly sensitive and rapid fluorescence sensor for Cronobacter sakazakii was developed. • The advantage of sensor based on the excellent fluorescence of functionalized upconversion nanoparticles probes. • The quenching was mainly arising from the competitive combination of UCNPs probes and the anionic enzyme. • A broad linear range (1.1×10 2 -1.1 × 10 8 cfu mL −1 ) and a high sensitivity (3.2 × 10 1 cfu mL −1 ). • Cronobacter sakazakii in real samples (tap water, infant formula powder and goat milk powder) were successfully detected.

Highly Robust {In2}-Organic Framework for Efficiently Catalyzing CO2 Cycloaddition and Knoevenagel Condensation.

To improve the catalytic performance of metal-organic frameworks (MOFs), creating higher defects is now considered as the most effective strategy, which can not only optimize the Lewis acidity of metal ions but also create more pore space to enhance diffusion and mass transfer in the channels. Herein, the exquisite combination of scarcely reported [In2(CO2)5(H2O)2(DMF)2] clusters and 2,6-bis(2,4-dicarboxylphenyl)-4-(4-carboxylphenyl)pyridine (H5BDCP) under solvothermal conditions generated a highly robust nanoporous framework of {[In2(BDCP)(DMF)2(H2O)2](NO3)}n (NUC-65) with nanocaged voids (14.1 Å) and rectangular nanochannels (15.94 Å × 11.77 Å) along the a axis. It is worth mentioning that an In(1) ion displays extremely low tetra-coordination modes after the thermal removal of its associated four solvent molecules of H2O and DMF. Activated {[In2(BDCP)](Br)}n (NUC-65Br), as a defective material because of its extremely unsaturated metal centers, could be generated by bromine ion exchange, solvent exchange, and vacuum drying. Catalytic experiments proved that the conversion of epichlorohydrin with 1 atm CO2 into 4-(chloromethyl)-1,3-dioxolan-2-one catalyzed by 0.11 mol % NUC-65Br could reach 99% at 65 °C within 24 h. Moreover, with the aid of 5 mol % cocatalyst n-Bu4NBr, heterogeneous NUC-65Br owns excellent universal catalytic performance in most epoxides under mild conditions. In addition, NUC-65Br, as a heterogeneous catalyst, exhibits higher activity and better selectivity for Knoevenagel condensation of aldehydes and malononitrile. Hence, this work offers a fresh insight into the design of structure defect cationic metal-organic frameworks, which can be better applied to various fields because of their promoted performance.

Cationic metal-organic framework with charge separation effect as a high output triboelectric nanogenerator material for self-powered anticorrosion.

New stable frictional materials based on metal-organic frameworks (MOFs) are greatly desired for applications in self-powered systems. This work reports an ionic MOF material with efficient charge separation mediated by charge induction. ZUT-iMOF-1(Cu) is chemically stable and its triboelectric output performance surpasses those of traditional MOF materials. The short-circuit current of the iMOF triboelectric nanogenerator is 73.79 μA at 5 Hz. The output performance remains stable over 50 000 cycles of continuous operation. The charge and power densities peak at 123.20 μC m-2 and 3133.23 mW m-2. Owing to its high output performance, ZUT-iMOF-1(Cu) effectively prevents metal corrosion in cathodic-protection systems. Theoretical calculations show that increasing the charge-separation effect promotes the frictional electricity generation behaviour. This study provides research suggestions for ionic MOF frictional materials and will promote their application in self-powered electrochemical cathodic-protection systems.

Water-based synthesis and nitrate release properties of a ZrIV-based metal-organic framework derived from L-aspartic acid.

We report the synthesis and characterisation of a cationic metal-organic framework (MOF) based on ZrIV and L-aspartate and containing nitrate as an extra framework counteranion, named MIP-202-NO3. The ion exchange properties of MIP-202-NO3 were preliminarily investigated to evaluate its potential as a platform for controlled release of nitrate, finding that it readily releases nitrate in aqueous solution.

Effectively Decontaminating Protein-Bound Uremic Toxins in Human Serum Albumin Using Cationic Metal-Organic Frameworks.

In the field of replacement of conventional dialysis treatment, searching superior materials for removal of protein-bound uremic toxins is a challenge on account of strong interactions between proteins and uremic toxins. Herein, we first adopted cationic metal-organic frameworks (MOFs), ZJU-X6 and ZJU-X7, as sorbents to decontaminate uremic toxins (p-cresyl sulfate and indoxyl sulfate). ZJU-X6 and ZJU-X7 exhibited innate advantage for sequestration of uremic toxins by utilizing a positive charge framework with exchangeable anions. Especially, ZJU-X6 showed a higher sorption capacity and faster sorption kinetics than those of most reported materials. Moreover, the cationic MOF materials could selectively remove uremic toxins even if in the presence of competitive chloride ions and proteins. Meanwhile, pair distribution function (PDF) and density functional theory (DFT) were employed to elucidate the sorption mechanism between uremic toxins and sorbents. This work suggests an attractive avenue for constructing new types of sorbents to eliminate uremic toxins for uremia treatment.

Twofold Interpenetrated Cationic Metal-Organic Framework with Hydrophobic Channels for Effectively Trapping Toxic Oxo-Anions.

Sequestration of toxic oxo-anions (such as 99TcO4- and ClO4-) from wastewater has received constant attention due to the existing serious threat to public health and the sustainability of the environment. In view of the low energy of hydration of TcO4- and ClO4-, cationic metal-organic framework (MOF) materials with the hydrophobic microenvironment are preferred in the selection of sorbents. Herein, a twofold interpenetrated cationic MOF (ZJU-X15) with double-helical chains was constructed by tetrakis[4-(pyridin-4-yl)phenyl]ethene (TPPE) and Cd2+ for the elimination of 99TcO4- and ClO4-. Profiting from hydrophobic channels, ZJU-X15 could remove most of ReO4- (a surrogate for 99TcO4-) and ClO4- in less than 10 and 20 min, respectively. As the result of batch experiments, ZJU-X15 could capture 356 mg of ReO4- and 221 mg of ClO4- per 1 g of sorbent, showcase decent selectivity, and still maintain high removal efficiency for anions after four recycles. Furthermore, the process of anion-exchange was confirmed by ion chromatography, Fourier-transform infrared spectroscopy, scanning electron microscopy combined with an energy-dispersive X-ray spectrometer, and X-ray photoelectron spectroscopy, indicating that target anions successfully entered into the body of ZJU-X15 through anion exchange.

Cationic Metal–Organic Frameworks Synthesized from Cyclotetraphosphazene Linkers with Flexible Tentacles

Cationic Metal–Organic Frameworks Synthesized from Cyclotetraphosphazene Linkers with Flexible Tentacles