Facile CO2 Separation in Composite Membranes

CO₂ emission from anthropogenic sources has raised worldwide environmental concerns and hence proficient energy paradigm has tilted towards CO₂ capture. Membrane technology is one of the efficient technologies for CO₂ separation since it is environmentally friendly, inexpensive, and offers high surface areas. Various approaches are discussed to improve membrane performance focusing mainly on permeability and selectivity parameters. Different types of fillers are incorporated to reach the Robeson's upper bound curve. In this review, polymer‐inorganic nanocomposite membranes for the separation of CO₂, CH₄, and N₂ from various gas mixtures are comprehensively discussed. Metal organic frameworks (MOFs) and ionic liquid (ILs) mixed‐matrix membranes are also considered.     

Fabrication of zeolitic imidazolate frameworks based mixed matrix membranes and mass transfer properties of C4H6 and N2 in membrane separation

1,3-Butadiene (BD) is a petrochemical-based volatile organic compound, extensively used for the manufacture of synthetic rubber. There is no method reported for its recovery from nitrogen mixture. Herein, for the first time, BD is efficiently recovered by gas separation through facile and novel mixed-metal ZIF-8 based mixed matrix membranes (MMMs). Addition of Ni-ZIF-8 nanoparticles in PDMS matrix, significantly improved the penetrant-membrane interactions and the solution-diffusion properties of BD. Positron annihilation lifetime spectroscopy analysis showed that the well dispersion of Ni-ZIF-8 in PDMS enhanced the free volume of membrane and created efficient continuous paths for BD diffusion. Then, 15 wt% Ni-ZIF-8 MMM exhibited the BD permeance of 323 GPU and the BD/N₂ ideal selectivity of 19.5, which were 60 and 81% higher than pure PDMS membrane, respectively. The simultaneous enhancement of BD permeance and BD/N₂ ideal selectivity indicated that Ni-ZIF-8 was an effective filler applied in MMMs for efficient BD recovery.     

Pillar[6]arene-based Molecular Trap with Unusual Conformation and Topology

A new low-density pillar[6]arene-based SOF (P6-SOF-2) with unusual topology of 3D uninodal 6-connected pcu alpha-Po primitive cubic topology for P6 was successfully constructed. In P6-SOF-2, each P6 ring adopts unprecedented C₂ symmetric chair-like conformation. More importantly, P6-SOF-2 owned 3D interconnected channels and large void volume, which would facilitate gas molecule transportation and adsorption. Binding sites, binding energies and interactions of C₂H₂, CO₂ and C₂H₄ were investigated via SCC-DFTB calculations. These gases preferred to trap in unguiculate intrinsic cavity of P6, like a molecular trap. Governed by size-exclusive effect and van der Waals interactions, the order of the binding of the adsorbed gases by P6-SOF-2 is CO₂>C₂H₂>C₂H₄, which facilitates the possible selective adsorption properties. Our study opens new perspectives in the development of SOFs.     

Metal-Organic Frameworks: A New Platform for Enzyme Immobilization

Metal-organic frameworks (MOFs) with attractive properties such as high surface area, tunable porosity, designable functionality and excellent stability, have aroused great interest from researchers as the matrices for enzyme immobilization. Recently, several efficient strategies including surface immobilization, post-synthetic infiltration and in situ encapsulation have been explored. MOF-immobilized enzymes, named enzymes@MOFs, show remarkably enhanced stability and recyclability, accelerating cell-free biocatalysis in diverse applications. This concept will impart the typical strategies for enzyme immobilization with MOFs, and their potential applications.     

新型金属有机骨架材料催化剂选择性催化还原氮氧化物研究进展

综述新型有机金属骨架材料和复合金属骨架材料催化剂在选择性催化还原氮氧化物方面的研究进展,讨论金属有机骨架材料催化剂的低温脱硝活性和抗硫抗水性能,介绍脱硝反应过程中氮氧化物的反应机理。针对金属有机骨架材料表现出的良好低温脱硝活性,认为其有可能替代传统脱硝催化剂。     

金属有机骨架UiO-66在催化领域的应用

金属有机骨架（MOFs）经过二十多年的快速发展,已经合成了成千上万种,然而MOFs材料普遍具有较低的稳定性,在一定程度上限制了MOFs的发展。UiO-66的合成是MOFs材料稳定性的一个突破,其在催化领域的发展尤为迅速。本文首先介绍了理想及实际状态下UiO-66的结构特征,并说明了配体缺失导致的节点空位处的元素组成。然后综述了利用UiO-66特殊的结构特征或将其功能化用于催化反应的研究,包括节点空位、功能化节点空位、负载金属纳米颗粒、功能化配体等。最后,考虑到可以综合利用UiO-66的特殊结构,对UiO-66在未来多功能催化剂的设计合成领域所能发挥的作用进行展望。     

双金属异相催化剂Fe3O4@La-MOF-Schiff-Pd/Ni的制备及其催化Suzuki偶联反应

将Fe3O4纳米粒子负载到金属有机骨架La-MOF中,然后向其中引入Pd/Ni活性位点,制得含磁性纳米粒子的Pd/Ni双金属异相催化剂（Fe3O4@La-MOF-Schiff-Pd/Ni）,并通过SEM、TEM、EDS、ICP、PXRD和XPS对其进行了表征。结果表明,Fe3O4纳米粒子被成功嵌入到了La-MOF中,经过后合成修饰后,Pd和Ni活性位点被均匀分散在MOF框架中。该催化剂在Suzuki偶联反应中表现出较高的催化活性,以碘苯(1.0 mmol)和苯硼酸(1.2 mmol)为反应物时,最佳催化反应条件为：以无水乙醇为溶剂、无水碳酸钾为碱、反应温度80℃、反应时间为6 h、催化剂用量8 mg,在此条件下联苯产率达95%。该催化剂可以通过外加磁铁进行分离回收,经过5次循环使用后仍然保持较高的催化活性,产物产率为82%。Suzuki偶联反应机理探究结果表明,Pd和Ni可能具有协同催化效应。底物拓展实验表明,Fe3O4@La-MOF-Schiff-Pd/Ni双金属催化剂对含不同取代基的芳基溴化物和碘化物具有较好的普适性。     

Adsorption Behavior of Halogenated Anesthetic and Water Vapor on Cr‐Based MOF (MIL‐101) Adsorbent. Part II. Multiple‐Cycle Breakthrough Tests

Multiple‐cycle breakthrough tests of a binary gas mixture of the halogenated anesthetic sevoflurane (SF) and water vapor were performed on both the synthesized chromium‐based metal organic framework (Cr‐MOF) and a conventionally used reference adsorbent. At 1 vol % SF and 50 % relative humidity mixture composition, the Cr‐MOF (MIL‐101) showed a significantly higher SF adsorption capacity, lower water vapor adsorption capacity, and no roll‐up effect compared to the reference sample. After each adsorption measurement, the saturated column was regenerated. MIL‐101 showed higher stability with minor SF capacity loss after 14 cycles, while the reference sample lost about a half of the SF capacity after 17 cycles.     

Performance-Enhanced and Washable Triboelectric Air Filter Based on Polyvinylidene Fluoride/UiO-66 Composite Nanofiber Membrane

Applying triboelectric nanogenerators (TENGs) in air filtration systems to generate electric charges through friction is a major advancement in air cleaning technology. The performance of triboelectric air filter strongly depends on the properties of triboelectric materials. In this work, a better triboelectric material, polyvinylidene fluoride (PVDF)/UiO-66 composite nanofiber membrane (P6-NFM), is designed and fabricated through electrospinning technology by doping UiO-66 into PVDF matrix. As the weight ratio of UiO-66 increases to 1%, PVDF/UiO-66 composite nanofiber-based TENG (P6-TENG) achieves the maximum current, voltage, and triboelectric charge of 4.29 µA, 52.8 V, and 22.02 nC, which are 6.5 times, 5.1 times, and 8.0 times as large as those of pure PVDF-based TENG (P-TENG). Therefore, the triboelectric air filter based on P6-NFM can be easily charged by slapping the fiber membrane and spun-bond fabric. After charging, the removal efficiency of P6-NFM is 92% for PM_0.5 and 98% for PM_2.5, which are 2.8 and 1.2 times those of the uncharged one. More importantly, the filtration efficiency of this air filter keeps stable after the membrane is washed four times. This method of loading UiO-66 on the triboelectric fiber material shows tremendous potential in self-charging and reusable air purification applications.     

Microstructure and properties of inter-locked mullite framework prepared by the TBA-based gel-casting process

Inter-locked mullite frameworks (IM frameworks) were prepared by the tert butyl alcohol (TBA) -based gel-casting method. The inter-locked structure formed through fluorine-catalyzed gas-phase reaction. Inter-locked topaz structure first formed in the samples and then it transformed into inter-locked mullite structure. TBA's volatilization and gaseous reactants' running off, which acted as two kinds of “pore formers” in the gel-casting process, offered enough space for the mullite grains' anisotropic growth, and led to the porous structure's formation. The volume density, apparent porosity, specific surface area and compression strength of the samples that formed at 1100–1500 °C were found to be 0.53–0.59 g/cm³, 82.1–76.1%, 12.3–4.6 m²/g and 1.6–3.6 MPa, respectively, indicating that the IM frameworks are promising as high-temperature catalyst supports.