Octanuclear Cobalt(II) Cluster-Based Metal-Organic Framework with Caged Structure Exhibiting the Selective Adsorption of Ethane over Ethylene

Novel ZIF-67-derived Co3O4 hollow nanocages as efficient nanozymes with intrinsic dual enzyme-mimicking activities for colorimetric sensing

Nanozymes with multifaceted functionalities have accrued substantial interest as they provide an expanded spectrum of applications in comparison to their single-active nanozymes. In this endeavor, novel Co3O4 hollow nanocages (COHNs) derived from ZIF-67 were crafted adorned with the exceptional quality of dual-enzymatic prowess by employing a simple co-precipitation and pyrolysis technique, all the while meticulously exploring the intricacies of the catalyst mechanism. Kinetic analyses ascertained that the catalytic behavior of COHNs adhered to the archetypal dynamics of Michaelis-Menten, displaying a higher affinity for 3,3',5,5'-tetramethylbenzidine (TMB) compared to natural enzymes. Leveraging the exceptional peroxidase- and oxidase-mimicking activity of the COHNs, a visual colorimetric assay platform was established for the detection of H2O2, ascorbic acid (AA), and acid phosphatase (ACP), all of which showed high selectivity and good sensitivity. Significantly, by harnessing the enzyme mimic property of COHNs, quantitative detection of H2O2, AA, and ACP unveiled astoundingly low detection limits of 0.0046 µM, 0.15 µM, and 0.0068 mU∙mL-1, respectively. Moreover, the successful detection application in real samples attested to the superior stability and anti-interference ability of the colorimetric sensing system. This study not only provides a novel nanozyme boasting remarkably dual-enzymatic prowess, but also pioneers a rapid and sensitive method for environmental analysis and clinical diagnosis.

High-Purity Ethylene Production from Ethane/Ethylene Mixtures at Ambient Conditions by Ethane-Selective Fluorine-Doped Activated Carbon Adsorbents

Energy-efficient separation of light alkanes from alkenes is considered as one of the most important separations of the chemical industry today due to the high energy penalty associated with the applied conventional cryogenic technologies. This study introduces fluorine-doped activated carbon adsorbents, where elemental fluorine incorporation into the carbon matrix plays a unique role in achieving high ethane selectivity. This enhanced selectivity arises from specific interactions between surface-doped fluorine atoms and ethane molecules, coupled with porosity modulation. Consequently, an equilibrium ethane/ethylene selectivity of as high as 3.9 at 298 K and 1 bar was achieved. Furthermore, polymer-grade ethylene (purity >99.99%) with a productivity of 1.6 mmol/g was obtained in a breakthrough run at ambient conditions from a binary ethane/ethylene (1/9 v/v) mixture. The ethane selectivity of the fluorine-doped carbons was further elucidated through Monte Carlo simulations and density contours of the adsorbed components. In addition to the high ethane selectivity, the adsorbents exhibited a hydrophobic surface, high stability under moisture, and excellent regenerability over multiple adsorption-desorption cycles under both equilibrium and dynamic conditions, demonstrating a sustainable performance.

Metal-Organic Framework Featuring Cubic Caged Structures for One-Step Ethylene Purification from Ethylene/Ethane Mixtures

Separation of C2H6/C2H4 mixtures is of significant importance in the chemical industry but remains a challenge due to the physicochemical similarities of C2H6 and C2H4. Herein, a metal-organic framework (MOF), [Zn4(μ4-O)(PCTF)3]n (Zn-PCTF) (PCTF2-= 5-trifluoromethyl-1H-pyrazole-4-carboxylic), is provided for the removal of C2H6 from C2H6/C2H4 mixtures. Zn-PCTF displays a three-dimensional framework featuring one-dimensional pore channels with periodic bottleneck segments. The well-balanced C2H6 adsorption capacity (79.0 cm3 g-1 at 298 K) and C2H6/C2H4 selectivity (1.8) for Zn-PCTF under ambient conditions boost Zn-PCTF with highly promising potentials for efficient purification of C2H4 from C2H6/C2H4 mixtures, which is verified by the dynamic column breakthrough experiments. The well-matched caged pores and suitable pore chemistry (particularly the presence of abundant Lewis base sites (N, O, and F) on the pore surfaces) for C2H6 account for the high-performance C2H6/C2H4 separation of Zn-PCTF unveiled by computational simulations.

Mesoporous MOF Based on a Hexagonal Bipyramid Co8-Cluster: High Catalytic Efficiency on the Cycloaddition Reaction of CO2 with Bulky Epoxides

A mesoporous cobalt-based metal-organic framework (LCU-606) was synthesized based on a hexagonal bipyramid Co8(μ4-O)3 cluster and an N,N,N',N'-tetrakis-(4-benzoic acid)-1,4-phenylenediamine ligand (H4TBAP). LCU-606 featuring large pore diameters of 21.7 Å and exposed Lewis-acid metal sites could serve as an excellent heterogeneous catalyst for CO2 cycloaddition reaction with various epoxide substrates under mild conditions (1 atm CO2, 60 °C, and solvent free). In particular, when extending the substrates to bulkier ones, LCU-606 still shows high catalytic efficiency on account of the large pore aperture. Also, LCU-606 demonstrates high recyclability and stability in consecutive catalytic runs. Therefore, the high efficiency, recyclability, and generality on CO2 catalytic cycloaddition make LCU-606 a very promising heterogeneous catalyst for CO2 chemical fixation.

Recent advances in metal-organic frameworks for gas adsorption/separation

The unique structural advantage of metal-organic frameworks (MOFs) determines the great prospect and developability in gas adsorption and separation. Both ligand design and microporous engineering based on crystal structure are significant lever for coping with new application exploration and requirements. Focusing on the designable pore and modifiable frameworks of MOFs, this review discussed the recent advances in the field of gas adsorption and separation, and analyzed the host-guest interaction, structure-performance relations, and the adsorption/separation mechanism from ligand design, skeleton optimization, metal node regulation, and active sites construction. Based on the function-oriented perspective, we summarized the main research recently, and made an outlook based on the focus of microporous MOFs that require further attention in the structure design and industrial application.

One-Step Ethylene Purification by an Ethane-Screening Metal-Organic Framework

Efficient purification of ethylene (C₂H₄) from ethane (C₂H₆) is a crucial but daunting task for the chemical industry given their similar physical natures and molecular dimensions. Reversed capture of C₂H₆ from C₂H₆/C₂H₄ dual-mixtures can be expected to directly yield high-purity C₂H₄ through a one-step separation unit, but it remains a daunting challenge. Here, we skillfully target an unusual "electrostatic-driven linker microrotation" (EDLM) in a Zr-MOF through coupling dual-ligands having electron-withdrawing/donating groups (e.g., F and CH₃ motifs). EDLM triggered microrotation of linker geometry and screening sites not only enhanced structural rigidity and hydrophobic nature, etc., but also effectively purified C₂H₄ through reversely trapping C₂H₆. Under ambient conditions, 1 kg of activated 2 adsorbents directly produces 7.2 L of C₂H₄ with over 99.9%+ purity in a single breakthrough operation starting from the equimolar C₂H₆/C₂H₄ cracked mixtures. Geometrical models and simulations have revealed that EDLM-derived H-bonding interaction and microrotation of linker geometry, synergistically customized C₂H₆-selective screening sites and pore inert for reversed C₂H₆ capture and improved surface hydrophobicity. Adsorption isotherms, modeling simulations, and breakthrough tests based on pressure swing adsorption (PSA) conditions have jointly elucidated the underlying separation properties for C₂H₄ purification. The enhanced hydrophobic nature, cycling durability, and separation property awarded 2 a new benchmark adsorbent to purify the olefin/paraffin mixtures.

Improving Ethane/Ethylene Separation Performance of Isoreticular Metal-Organic Frameworks via Substituent Engineering

The preferential capture of ethane (C₂H₆) over ethylene (C₂H₄) presents a very cost-effective and energy-saving means applied to adsorptive separation and purification of C₂H₄ with a high product purity, which is however challenged by low selectivity originating from their similar molecular sizes and physical properties. Substituent engineering has been widely employed for selectivity regulation and improvement, but its effect on C₂H₆/C₂H₄ separation has been rarely explored to date. In this work, four isoreticular coordination framework compounds based on 5-(pyridin-3-yl)isophthalate ligands bearing different substituents were rationally constructed. As revealed by isotherm measurements, thermodynamic studies, and IAST computations, they exhibited promising utility for C₂H₆/C₂H₄ separation with moderate adsorption heat and a high uptake amount at a relatively low-pressure domain. Furthermore, the C₂H₆/C₂H₄ separation potential can be finely tuned and optimized via purposeful substituent alteration. Most remarkably, functionalization with a nonpolar methyl group yielded an improved separation efficiency compared to its parent compound. This work offers a good reference value for enhancing the C₂H₆/C₂H₄ separation efficiency of MOFs by engineering the pore microenvironment and dimensions via substituent manipulation.

A new multi-functional Cu(ii)-organic framework as a platform for selective carbon dioxide chemical fixation and separation of organic dyes

A new multi-functional metal–organic framework {[Cu2(HL)(H2O)2]·NMP·2H2O}n was synthesized. It shows efficient catalytic performance for the chemical fixation of CO2 and exhibits selective sorption towards the rhodamine B dye.