Uncoordinated Carboxylate Research Articles

Incorporation of Multiple Binding Sites into an Adaptive MOF for Sieving Butane Isomers

AbstractEfficient separation of liner alkanes from branched alkanes is of prime importance in the petrochemical industry. Herein an adaptive metal‐organic framework FJI‐H38 is reported with 1D channel which can vary delicately ≈4.0 Å. The activated FJI‐H38 displays extremely large butane (n‐C4H10) capacity, especially at low pressure (44.15 cm3 g−1 at 298 K and 0.1 bar), but barely adsorbs isobutane (iso‐C4H10). Remarkably, FJI‐H38 possesses a high n‐C4H10/iso‐C4H10 selectivity of 246.75. Gas‐loaded single crystal X‐ray analysis and modeling calculation reveal that the synergetic effect of pore confinement and surfaces decorated with uncoordinated carboxyl group plays a critical role in the capture of the relatively smaller n‐C4H10 while the exclusion of the larger iso‐C4H10. In addition, dynamic breakthrough tests explicitly prove FJI‐H38 displays prominent separation performance for n/iso‐C4H10 under various conditions with ultra‐high productivity of high‐purity n‐C4H10 (42.48 L/kg, ≥99.0%) and iso‐C4H10 (42.35 L/kg, ≥99.95%).

Two Stable Pillar-Layered Zn-LMOFs for Highly Fluorescence Sensing of Inorganic Pollutants and Nitro Aromatic Compounds in Water.

Luminescent metal-organic frameworks (LMOFs) are a potential class of functional materials for the photoluminescent detection of a wide range of analytes as well as for the detection of pollutants in wastewater. Herein, by using the pillar-layered strategy, two new luminescence Zn-LMOFs (JLU-MOF222 and JLU-MOF223) were successfully solvothermal synthesized. The 2D layers are both consisting of Zn2+ and TPHC [TPHC = (1,1':2',1″-terphenyl)-3,3″,4,4',4″,5'-hexacarboxylic acid] ligands and then pillared by the different N-donor ligands to form the 3D Zn-LMOFs with fsh topology. Benefiting from the uncoordinated carboxylate sites, uncoordinated N atom, or -NH2 group in the pillaring ligands and excellent stability in pH = 2-13 aqueous phase, JLU-MOF222 and JLU-MOF223 not only can sensitively detect trace amounts of inorganic pollutants (Fe3+, Cr2O72-) and nitro aromatic compounds TNP and 2,4-DNP (TNP = 2,4,6- trinitrophenol, 2,4-DNP = 2,4-dinitrophenol) through luminescence quenching but also exhibit high selectivity of other anti-interference competing analytes. The two new Zn-LMOFs can be used as potential luminescent sensors for pollutant detection in water due to their high KSV and low limit of detection (LOD).

Multifunctional and Ultrastable Co-MOF Effectively Separates Various Different Component Gas Mixtures.

Developing low-cost and multifunctional adsorbents for adsorption separation to obtain high-purity (>99.9%) gases is intriguing yet challenging. Notably, the ongoing trade-off between adsorption capacity and selectivity in separating multicomponent mixed gases still persists as a pressing scientific challenge requiring urgent attention. Herein, the ultrastable TJT-100 exhibits unique structural characteristics including uncoordinated carboxylate oxygen atoms, coordinated water molecules directed toward the pore surface, and sufficient Me2NH2+ cations in channels. TJT-100 exhibits a high adsorption capacity and exceptional separation performance, particularly notable for its high C2H2 capacity of 127.7 cm3/g and remarkable C2H2 selectivity over CO2 (5.4) and CH4 (19.8), which makes it a standout material for various separation applications. In a breakthrough experiment with a C2H2/CO2 mixture (v/v = 50/50), TJT-100 achieved a record-high C2H2 productivity of 69.33 L/kg with a purity of 99.9%. Additionally, TJT-100 demonstrates its effectiveness in separating CO2 from natural gas and flue gas. Its exceptional selectivity for CO2/CH4 (10.7) and CO2/N2 (11.9) results in a high CO2 productivity of 21.23 and 22.93 L/kg with 99.9% purity from CO2/CH4 (v/v = 50/50) and CO2/N2 (v/v = 15/85) mixtures, respectively.

Rationally designed nanotrap structures for efficient separation of rare earth elements over a single step

Extracting rare earth elements (REEs) from wastewater is essential for the growth and an eco-friendly sustainable economy. However, it is a daunting challenge to separate individual rare earth elements by their subtle differences. To overcome this difficulty, we report a unique REE nanotrap that features dense uncoordinated carboxyl groups and triazole N atoms in a two-fold interpenetrated metal-organic framework (named NCU-1). Notably, the synergistic effect of suitable pore sizes and REE nanotraps in NCU-1 is highly responsive to the size variation of rare-earth ions and shows high selectivity toward light REE. As a proof of concept, Pr/Lu and Nd/Er are used as binary models, which give a high separation factor of SFPr/Lu = 796 and SFNd/Er = 273, demonstrating highly efficient separation over a single step. This ability achieves efficient and selective extraction and separation of REEs from mine tailings, establishing this platform as an important advance for sustainable obtaining high-purity REEs.

Carboxyl-Decorated UiO-66 Supporting Pd Nanoparticles for Efficient Room-Temperature Hydrodeoxygenation of Lignin Derivatives.

Hydrodeoxygenation (HDO) of lignin derivatives at room-temperature (RT) is still of challenge due to the lack of satisfactory activity reported in previous literature. Here, it is successfully designed a Pd/UiO-66-(COOH)2 catalyst by using UiO-66-(COOH)2 as the support with uncoordinated carboxyl groups. This catalyst, featuring a moderate Pd loading, exhibited exceptional activity in RT HDO of vanillin (VAN, a typical model lignin derivative) to 2-methoxyl-4-methylpheonol (MMP), and >99% VAN conversion with >99% MMP yield is achieved, which is the first metal-organic framework (MOF)-based catalyst realizing the goal of RT HDO of lignin derivatives, surpassing previous reports in the literature. Detailed investigations reveal a linear relationship between the amount of uncoordinated carboxyl group and MMP yield. These uncoordinated carboxyl groups accelerate the conversion of intermediate such as vanillyl alcohol (VAL), ultimately leading to a higher yield of MMP over Pd/UiO-66-(COOH)2 catalyst. Furthermore, Pd/UiO-66-(COOH)2 catalyst also exhibits exceptional reusability and excellent substrate generality, highlighting its promising potential for further biomass utilization.

Bioinspired trimesic acid anchored electrocatalysts with unique static and dynamic compatibility for enhanced water oxidation

Layered double hydroxides are promising candidates for the electrocatalytic oxygen evolution reaction. Unfortunately, their catalytic kinetics and long-term stabilities are far from satisfactory compared to those of rare metals. Here, we investigate the durability of nickel-iron layered double hydroxides and show that ablation of the lamellar structure due to metal dissolution is the cause of the decreased stability. Inspired by the amino acid residues in photosystem II, we report a strategy using trimesic acid anchors to prepare the subsize nickel-iron layered double hydroxides with kinetics, activity and stability superior to those of commercial catalysts. Fundamental investigations through operando spectroscopy and theoretical calculations reveal that the superaerophobic surface facilitates prompt release of the generated O2 bubbles, and protects the structure of the catalyst. Coupling between the metals and coordinated carboxylates via C‒O‒Fe bonding prevents dissolution of the metal species, which stabilizes the electronic structure by static coordination. In addition, the uncoordinated carboxylates formed by dynamic evolution during oxygen evolution reaction serve as proton ferries to accelerate the oxygen evolution reaction kinetics. This work offers a promising way to achieve breakthroughs in oxygen evolution reaction stability and dynamic performance by introducing functional ligands with static and dynamic compatibilities.

A free carboxyl-decorated metal-organic framework with 3D helical chirality for highly enantioselective recognition

With the judicious selection of a designed polycarboxylate derived from L-phenylalanine, (S)-5-(((1-carboxy-2-phenylethyl)amino)methyl)isophthalic acid (H3L), a novel homochiral metal-organic framework decorated with a free carboxyl, {[Cu2(HL)2(bipy)]∙2H2O}n (Cu-MOF), has been designed and synthesized in a solvothermal process. The result of single crystal X-ray diffraction analysis showed that Cu-MOF had the character of a three-dimensional structure with helical chirality. As we expected, in Cu-MOF, one accessible free carboxylic acid group on H3L pointed toward the spiral channels, and the other two –COOH groups were utilized in bonding. The enantioseparation performance of Cu-MOF was thoroughly investigated and the results showed that Cu-MOF can specifically recognize S-1-(1-naphthyl) ethanol (S-NE) with enantiomeric excess (ee) value of 99.35 %, which was much higher than the other three racemates. The appropriate size together with suitable interaction sites played an important role in enantioseparations. Inspired by the excellent chiral recognition effects towards S-NE, the chiral recognition mechanism was experimentally clarified. A fully agreement observed in 13C CP MAS NMR analysis as well as the X-ray photoelectron spectroscopy (XPS) determination revealed that a strong hydrogen bonding interaction forces existed between the hydroxyl of the optical S-NE and the decorated –COOH in the chiral framework. The control experiment further identified the decisive role of the uncoordinated carboxyl group in Cu-MOF. In addition, the strong intermolecular off-set π-π interactions between the phenyl ring involved with the coordinated COO− groups in Cu-MOF and the naphthyl ring of S-NE, was the another important factor for the specifical enantioseparation of S-enantiomer. On the basis of strong intermolecular hydrogen bonding, NE racemates were enantioselective discriminated and enantiomeric purity can be determined by means of Raman scattering spectroscopy.

Microporous Cd-MOF as multifunctional material for rapid and visual luminescence sensing of Fe3+, MnO4− and TNP in water and efficient CO2 catalytic conversion

The excessive discharge of Fe3+, MnO4−, TNP and CO2 has resulted in serious environmental problems, which needs to be resolved urgently. Herein, a stable multifunctional Cd2+-organic framework, [Cd(H4L)]·2DMF·8H2O (Cd-MOF-1) was successfully constructed by using the ligand 4,4′,4″,4‴- (1,4-phenylenebis (1H-imidazole-2,4,5-triyl))tetrabenzoic acid (H6L) and Cd(NO3)2·2.5H2O under solvothermal conditions. Structural analysis revealed that Cd-MOF-1 possessed a 3D framework with rich Lewis acid sites (unsaturated Cd2+ sites), Brønsted acid sites (protonated imidazole moieties) and uncoordinated carboxylate oxygens in the hexagonal 1D channels. Moreover, Cd-MOF-1 exhibits good stability in acid-base aqueous solutions with pH = 4–12. Apart from the above structural features, Cd-MOF-1 also displays intense luminescence emission, which can be used to quickly and sensitively detect Fe3+, MnO4−and TNP in aqueous solutions with a high quenching constant and low detection limit even in the presence of other competition ions. Especially, the response time of the Cd-MOF-1 for Fe3+ ions was only 5 s, which is very short response time among the previous MOFs used for Fe3+ detection. Besides, we successfully constructed Cd-MOF-1/PEO mixed matrix films, which can achieve visualized quick detection of Fe3+, MnO4−and TNP in aqueous solutions under the UV lamp. In addition, activated Cd-MOF-1 (called Cd-MOF-1a) with all the guest molecules removed by heating delineates medium shows CO2 gas adsorption and efficient CO2 fixation with epoxide into cyclic carbonate under relatively mild and solvent-free conditions. On top of that, Cd-MOF-1 can be reused at least five cycles with excellent luminescence efficiency and catalytic activity. Furthermore, the possible luminescence sensing and catalytic mechanisms have also been discussed in detail. This work gives a new multifunctional platform for luminescence sensing and CO2 fixation.

Proton conductive properties of one water-stable nickel(II) supramolecule bearing tri-pyridyl and tri-carboxylate ligand

The construction of highly stable complexes using azacyclic carboxylate ligands is an important way to obtain crystalline proton-conducting materials with high performance. In this paper, one three-dimensional supramolecule, [Ni(H2ttp)2]⋅3H2O (1) [H3ttp = 4-(2,4,6-tricarboxyphenyl)-2,2′,6,2′′-terpyridine] has been prepared according to literature approach with slight modification. Firstly, its molecular structure was determined by powder X-ray diffraction, infrared spectroscopy, and elemental analysis, followed by a thermogravimetric determination to confirm its thermal and water stability. The N2 and water H2O adsorption abilities were also measured. Electrochemical experiments have shown 1 to be a typical temperature and humidity-dependent proton conductor with an optimum proton conductivity of 4.00 × 10−4 S/cm (98% RH/100 °C). A large number of uncoordinated carboxylate units and crystalline water molecules, as well as the H-bonding networks inside the framework, provide effective channels for proton transportation. The proton-conductive mechanism was further postulated following the calculated value of activation energy.

Adenine-mediated amide-containing metal-organic framework toward one-step ethylene purification from a ternary mixture

Simultaneous removal of acetylene (C2H2) and ethane (C2H6) from a ternary gas mixture of acetylene/ethylene/ethane via a one-step process to achieve high purity of ethylene (C2H4) is challenging but highly desirable. Herein, an amide-containing adenine-mediated rod metal-organic framework (MOF) of 1 was solvothermally constructed by means of mixed-linker approach. Structural analysis illustrates that 1 displays 1D microporous channels and features open metal site-free concomitant with uncoordinated carboxylate oxygen atoms and amide functional groups decorated interior pore walls. Interestingly, both single-component gas adsorption and ideal adsorbed solution theory (IAST) prediction reveal that 1 is C2H2 and C2H6 selective, which were eventually confirmed by dynamic column breakthrough experiments through not only binary gas mixtures of C2H2/C2H4 and C2H6/C2H4, but also a ternary mixture of C2H2/C2H4/C2H6 to validate one-step ethylene purification.

Nanosheets of two-dimensional photoluminescent lanthanide phosphonocarboxylate frameworks decorated with free carboxylic groups for latent fingerprint imaging.

The synthesis, structural characterization, exfoliation, and photophysical studies of two-dimensional (2-D) lanthanide phosphonates, named Ln(m-pbc); [Ln(m-Hpbc)(m-H2pbc)(H2O)] (Ln = Eu, Tb; m-pbc = 3-phosphonobenzoic acid) based on the phosphonocarboxylate ligand, are reported. These compounds are neutral polymeric 2D layered structures with pendent uncoordinated carboxylic groups between layers. The nanosheets were obtained by a top-down strategy involving sonication-assisted solution exfoliation and characterized by atomic force microscopy and transmission electron microscropy, showing lateral dimensions from nano- to micro-meter scales, and thicknesses down to several layers. The photoluminescence studies demonstrate that the m-pbc ligand acts as an efficient antenna toward Eu and Tb(III) ions. The emission intensities of dimetallic compounds are clearly enhanced after incorporation of Y(III) ions due to the dilution effect. Ln(m-pbc)s were then applied for labelling latent fingerprints. It is worth noting that the reaction between active carboxylic groups and fingerprint residues benefits the labelling, showing efficient imaging for fingerprints on all kinds of material surfaces.

Rational Synthesis of a Stable Rod MOF for Ultrasensitive Detection of Nitenpyram and Nitrofurazone in Natural Water Systems.

Overuse of nitenpyram and nitrofurazone in agricultural products poses enormous risks to ecosystems, and effective detection and quantification of these residual pollutants are of great concern. Although several strategies have been established for detecting nitenpyram and nitrofurazone in water, searching for a new sensor material with great sensitivity, selectivity, and recyclability remains challenging. Here, we design and synthesize a stable metal-organic framework (MOF) (Zn-CPTA) by employing an organic linker based on the coordination features of benzene-1,4-dicarboxylate and picolinic acid. Zn-CPTA is a 3D framework built from Zn-O-Zn chains called rod secondary building units, which contains 1D open channels modified by uncoordinated carboxyl O atoms and exhibits impressive chemical stability in aqueous solutions within a pH range from 2 to 12. Especially, fluorescent Zn-CPTA can quickly and sensitively detect nitenpyram and nitrofurazone in aqueous solutions with a high quenching constant and low detection limit (LOD) (KSV values for nitenpyram and nitrofurazone are 1.67 × 104 and 1.02 × 105 M-1 with LOD of 0.625 and 0.126 μM, respectively), as well as outstanding selectivity and recyclability. Notably, the LOD value is the lowest among the reported MOFs used for nitrofurazone detection. Besides, experiments and density functional theory calculations are combined to explain the quenching mechanism. Finally, the practical application of Zn-CPTA was further explored in real environment samples with satisfactory recoveries.

Highly Sensitive Adsorption and Detection of Iodide in Aqueous Solution by a Post-Synthesized Zirconium-Organic Framework

Effective methods of detection and removal of iodide ions (I-) from radioactive wastewater are urgently needed and developing them remains a great challenge. In this work, an Ag+ decorated stable nano-MOF UiO-66-(COOH)2 was developed for the I- to simultaneously capture and sense in aqueous solution. Due to the uncoordinated carboxylate groups on the UiO-66-(COOH)2 framework, Ag+ was successfully incorporated into the MOF and enhanced the intrinsic fluorescence of MOF. After adding iodide ions, Ag+ would be produced, following the formation of AgI. As a result, Ag+@UiO-66-(COOH)2 can be utilized for the removal of I- in aqueous solution, even in the presence of other common ionic ions (NO2-, NO3-, F-, SO42-). The removal capacity as high as 235.5 mg/g was calculated by Langmuir model; moreover, the fluorescence of Ag+@UiO-66-(COOH)2 gradually decreases with the deposition of AgI, which can be quantitatively depicted by a linear equation. The limit of detection toward I- is calculated to be 0.58 ppm.

High Water-Assisted Proton Conductivities of Two Cadmium(II) Complexes Constructed from Zwitterionic Ligands.

Finding more metal complexes with outstanding water stability and high proton conductivity still has important research significance for the energy field. Herein, two highly proton-conductive complexes, one hydrogen-bonded supramolecular framework (HSF) [Cd(CBIA)2(H2O)4]·2H2O (1) and one coordination polymer (CP), {[Cd2(CBIA)2(4,4'-bipy)2(H2O)2]·(CBIA)·(OH)·2H2O}n (2) (4,4'-bipy = 4,4'-bipyridine), were triumphantly assembled using a zwitterionic organic compound, 2-(1-(carboxymethyl)-1H-benzo[d]imidazol-3-ium-3-yl)acetate (HCBIA). In the structure of HSF 1, there are several coordination and lattice H2O units except for the two monodentate CBIA- anions. CP 2 with a one-dimensional (1D) cylindrical structure has free CBIA- units and free H2O units located in the cavity. Thanks to the ability of the uncoordinated carboxyl groups and coordination/lattice water molecules to construct the rich H-bonding networks, both complexes exhibit super-high proton conductivities, reaching 5.09 × 10-3 and 3.41 × 10-3 S cm-1 under 100 °C/98% relative humidity (RH), respectively. Based on the exploration of crystal structure data, combined with the calculated activation energy, and adsorption/desorption plots of nitrogen and water vapor, the causes and differences in proton conductivity of the two complexes, especially the proton-conductive mechanism, are compared and analyzed. This study again confirms that the zwitterionic ligands can exert important effects on forming organo-inorganic hybrid materials with high proton conductivity.

Carboxylate-mediated proton transfer promotes water oxidation on spindle-like Ce-doped FeCo hydroxide

The proton transfer plays a crucial, yet not well-control, role in enhancing the oxygen evolution reaction (OER) performance of transition metal (TM) (oxy) hydroxide materials. Herein, we take Ce-doped FeCo layered double hydroxide (Ce-FeCo LDH) nanosheets in situ growth on spindle-like MIL-88A, as a model system to demonstrate enhancing OER activity through the promotion of proton transfer by forming the carboxylate ligands coordinated with TM atoms. The carboxyl group-functionalized MIL-88A@Ce-FeCo LDH core–shell hybrid catalyst, fabricated by the one-pot reflux method, is made up of Ce-FeCo LDH as active component and carboxylate ligands as a proton acceptor. Specifically, the uncoordinated carboxylate ligands serve as relays to promote proton transfer and deprotonation efficiency. As a result, this core–shell structured hybrid exhibits superior OER activity while maintaining excellent durability. This work provides a facile method to reserve carboxylates as the station of proton transfer on TM-based catalyst to promote water splitting.

Simple preparation and efficient fluoride removal of La anchored Zr-based metal–organic framework adsorbent

Excess fluoride in drinking water from groundwater can cause dental and skeletal fluorosis affecting millions of people worldwide. Adsorption is an appealing strategy for defluoridation due to its simple operation and environmental friendliness. However, conventional adsorbents exhibit low adsorption capacity because few exposed active sites. In this work, La anchored Zr-based metal-organic framework (La-UiO-66-(COOH)2) adsorbent with dual-metal sites was designed and synthesized to remove fluoride effectively. The doping of La(III) using uncoordinated carboxyl group of UiO-66-(COOH)2 increased the adsorption capacity. The morphology, composition, structure, surface area, and thermal stability of adsorbent were carefully characterized by powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectrometer (EDX), fourier transform infrared (FT-IR), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS) techniques. The adsorbent is a polyhedral shape with aggregated and smaller crystalline particles and La is uniformly distributed over the adsorbent, favoring the effective adsorption of fluoride. La-UiO-66-(COOH)2 showed excellent adsorption performance in a wide pH range of 3–9, and the maximum adsorption capacity was 57.23 mg g−1. The fluoride removal rate of as-prepared adsorbent reached as high as 87 % within 5 min. The adsorption process conformed to the pseudo-second-order equation model and the Freundlich isotherm model. Thermodynamic research indicated that the adsorption process was spontaneous and endothermic. After four adsorption-desorption cycles, the fluoride removal rate of the adsorbent was still retained at 79.7%. The design of dual-metal site adsorbents provides a potential strategy for highly efficient removal of fluoride.

Photocatalytic properties of two new isostructural cobalt(II) and nickel(II) complexes having terphenyl-3,3″,4,4″-teteacarboxylic acid

The effective and rapid removal of organic pollutants from wastewater is very important for the safety of aquatic environment. Photocatalytic degradation is a feasible strategy that can safely eliminate the organic pollutants from the wastewater discharge. Amongst varied class of photocatalysts, the coordination polymers (CPs) are important class of material that can be used to remove and degrade the organic dyes from wastewater. Herein, two isostructural coordination polymers, having compositions [Ni2(H2L)2(phen)4·H4L·6H2O)] (1) and [Co2(H2L)2(bipy)4·H4L·6H2O)] (2) (H4L = terphenyl-3,3″,4,4″-teteacarboxylic acid, phen = 1,10-phenanthroline and bipy = 2,2′-bipyridine) have been synthesized and characterized. Both of the isostructural compounds display dinculear architecture, where metal centers are coordinated to two carboxylic groups, which further forms a 2D supramolecular layer via hydrogen bonds formed between the water molecules and uncoordinated carboxylate groups. Both the compounds have been used as photocatalysts to catalyze the photodegradation of methylene blue (MB) and methylene violet (MV) under UV irradiation. The Ni(II)-based photocatalyst 1 exhibited the good photocatalytic performance in comparison to that of 2. The observed differences in the photocatalytic properties of both the CPs have been addressed using Hirshfeld surface analyses.

Boosting electrochemical nitrate-ammonia conversion via organic ligands-tuned proton transfer

Electrochemical nitrate (NO3-) reduction reaction (NO3-RR) offers an ideal route to harvest ammonia (NH3) under ambient conditions. Despite recent advances in Cu-based NO3-RR electrocatalysts, their synthesis heavily relies on the regulation of adsorption strength towards nitrogen-containing intermediates, and other important factors are ignored (i.e., the proton transfer rate). Here, we select Cu nanoparticles (NPs) as model catalysts to investigate whether and how the proton transfer rate impacts the NO3-RR kinetics. The results indicate that the proton transfer is involved in the rate-determining step (RDS) of NO3-RR, and the weak water dissociation ability of Cu leads to slow proton transfer rate and consequently sluggish NO3-RR kinetics. To this end, we enhance the water dissociation ability of Cu NPs by incorporating uncoordinated carboxylate ligands to enable rapid proton transfer, which in turn boosts the hydrogenation of key intermediates for reducing the overall energy barrier of NO3-RR. As a result, Cu NPs with the ligands display a maximum NH3 yield rate of 496.4 mmol h−1 gcat−1, outperforming counterpart without ligands. This work not only deepens our knowledge on the NO3-RR mechanism, but also offers new guidelines for the smart design of efficient electrocatalysts.

Chemorobust 4p-5p {InPb}-organic framework for efficiently catalyzing cycloaddition of CO2 with epoxides and deacetalization-Knoevenagel condensation

Due to that the high charge density and small radius render In3+ cation a stronger Lewis acidity, multifunctional nanoporous In-MOFs have become one of the most promising catalysts for their high activity. Herein, the solvothermal self-assembly by employing 2,4,6-tri (2,4-dicarboxyphenyl)pyridine (H6TDP) as organic linker leads to a robust honeycomb skeleton of {[(CH3)2NH2][InIIIPbII(TDP) (H2O)]⋅3DMF⋅3H2O}n (NUC-52) with the merits of nanoscopic channels, high porosity (61.3%), large specific surface area, and thermal stability. To the best of our knowledge, this is the first 4p-5p heterometallic {InIIIPbII} cluster-based nano-porous host framework, whose activated state possesses the coexistence of Lewis acid-base sites including 7-coordinated Pb2+ ions, 4-coordinated In3+ ions, uncoordinated carboxyl oxygen atoms, and Npyridine atoms. Performed catalytic experiments exhibited that activated NUC-52 owned the high catalytic activity on the cycloaddition reactions of styrene oxide with CO2 under mild conditions with excellent turnover number (2475) and turnover frequency (619 h−1). Moreover, activated NUC-52 could greatly accelerate the deacetalization-Knoevenagel condensation reactions of benzaldehyde dimethyl acetal and malononitrile. Hence, this work lays down the groundwork for constructing heterometallic cluster-based nanoporous MOFs with excellent Lewis acidic catalysis and chemical stability, which should be ascribed to the reasonable coordination arrangement between organic ligands and distinct metal ions according to the hard–soft acid–base (HSAB) theory.

Simultaneous voltammetric determination of dopamine and uric acid based on MOF-235 nanocomposite

A highly selective and facile sensing platform based on MOF-235 is fabricated and explored for the synchronous detection of dopamine and uric acid. The MOF-235 material is prepared via a one-step hydrothermal method. The sensing platform is fabricated via drop casting of MOF-235 dispersion on bare glassy carbon electrode (GCE). Then it is sealed using chitosan solution. The as-prepared MOF-235 material has large amount of unsaturated iron metal ions available for electrochemically redox-driven transformation. The aromatic moieties and the uncoordinated carboxylate groups of the MOF-235 are capable of obtain well-separated signals for dopamine (DA) and uric acid (UA), which is attributed to the π-π interactions, hydrogen bond and electrostatic action. These characteristics endow the excellent permselectivity and sensitivity for the MOF-235 modified electrode. The designed sensing platform exhibits linear response over concentration range from 10 to 90 μM for DA, and 10 to 90 μM for UA with the detect limit of 3.34 μM for DA and 3.46 μM for UA separately. To our knowledge, this is the first attempt that MOF-235 is explored the applications in electrochemical determination of medical small molecules. The implementing of MOF-235 in voltammetric detection offers new opportunities for the development of MOF materials based electroanalytical devices.