Reversible Low-Temperature Metal Node Distortion during Atomic Layer Deposition of Al2O3 and TiO2 on UiO-66-NH2 Metal-Organic Framework Crystal Surfaces

Metal-Organic Framework (MOF)-Based Clean Energy Conversion: Recent Advances in Unlocking its Underlying Mechanisms

Carbon neutrality is an important goal for humanity . As an eco-friendly technology, electrocatalytic clean energy conversion technology has emerged in the 21st century. Currently, metal-organic framework (MOF)-based electrocatalysis, including oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), hydrogen oxidation reaction (HOR), carbon dioxide reduction reaction (CO2RR), nitrogen reduction reaction (NRR), are the mainstream energy catalytic reactions, which are driven by electrocatalysis. In this paper, the current advanced characterizations for the analyses of MOF-based electrocatalytic energy reactions have been described in details, such as density function theory (DFT), machine learning, operando/in situ characterization, which provide in-depth analyses of the reaction mechanisms related to the above reactions reported in the past years. The practical applications that have been developed for some of the responses that are of application values, such as fuel cells, metal-air batteries, and water splitting have also been demonstrated. This paper aims to maximize the potential of MOF-based electrocatalysts in the field of energy catalysis, and to shed light on the development of current intense energy situations.

Thermally-activated gelatin-chitosan-MOF hybrid aerogels for efficient removal of ibuprofen and naproxen

Nonsteroidal anti-inflammatory drugs (NSAIDs) are one of the most frequently used drugs and have been frequently detected in aquatic environments. This paper demonstrates a thermally-activated gelatin-chitosan and amine-functionalized metal-organic framework (UiO-66-NH2) aerogel (CGC-MOF), which was successfully synthesized for the efficient removal of ibuprofen (IBP) and naproxen (NPX). Various characterization tools were used to systematically analyze the microstructure and physicochemical properties of the synthesized aerogel. In addition, the effect of key reaction parameters as well as batch and continuous-flow fixed-bed column experiments were carried out to elucidate the adsorption process. Several functional groups in the biopolymer network, combined with excellent MOF properties, synergistically couple to form an adsorbent with great performance. The mesoporous aerogel activated at 200 °C (CGC-MOF200) exhibited a high specific surface area (819.6 m2/g) that is valuable in providing abundant adsorption active sites that facilitate the efficient adsorption of IBP and NPX. CGC-MOF200 exhibited an excellent removal of IBP and NPX, accounting to 99.28 % and 96.39 %, respectively. The adsorption process followed the pseudo-second-order kinetics and the Freundlich isotherm models, suggesting heterogeneous and chemisorption adsorption processes. Overall, this work provides new and valuable insights into the development of a promising biopolymer-MOF composite aerogel for environmental remediation.

Efficient removal of copper and silver ions in electroplating wastewater by magnetic-MOF-based hydrogel and a reuse case for photocatalytic application

Direct discharge of electroplating wastewater containing hazardous metal ions such as Cu2+ and Ag + results in environmental pollution. In this study, we rationally prepare a magnetic composite hydrogel consisted of Fe3O4, UiO-66-NH2, chitosan (CTS) and polyethyleneimine (PEI), namely Fe3O4@UiO-66-NH2/CTS-PEI. Thanks to the strong attraction between the amino group and metal cations, the Fe3O4@UiO-66-NH2/CTS-PEI hydrogel shows the maximum adsorption capacities of 321.67 mg g-1 for Cu2+ ions and 226.88 mg g-1 for Ag + ions within 120 min. As real scenario, the Fe3O4@UiO-66-NH2/CTS-PEI hydrogel exhibits excellent removal efficiencies for metallic ions even in the complicated media of actual electroplating wastewater. In addition, we explore the competitive adsorption order of metal cations by using experimental characterization and theoretical calculations. The optimal configuration of CTS-PEI is also discovered with the density functional theory, and the water retention within hydrogel is simulated through molecular dynamics modeling. We find that the Fe3O4@UiO-66-NH2/CTS-PEI hydrogel could be reused and after 5 cycles of adsorption-desorption, removal efficiency could maintain 80%. Finally, the Ag+ accumulated by hydrogel are reduced to generate a photocatalyst for efficient degradation of Rhodamine B. The novel magnetic hydrogel paves a promising path for efficient removal of heavy metal ions in wastewater and further resource utilization as photocatalysts.

Controlled Partial Linker Thermolysis in Metal-Organic Framework UiO-66-NH2 to Give a Single-Site Copper Photocatalyst for the Functionalization of Terminal Alkynes

Metal-organic frameworks (MOFs) with expanding porosity and tailored pore environments are intriguing for catalytic applications. We report herein a straightforward method of controlled partial linker thermolysis to introduce desirable mesopores into mono-ligand MOFs, which is different from the classical thermolyzing method that starts from mixed-linker MOFs. UiO-66-NH2 , after partial ligand thermolysis, exhibits significant mesoporosity, retained crystal structure, improved charge photogeneration and abundant anchoring sites, which is ideal to explore single-site photocatalysis. Atomically dispersed Cu is then accommodated in the tailored pore. The resulting single-site Cu catalyst exhibits excellent performance for photocatalytic alkylation and oxidation coupling for the functionalization of terminal alkynes. The study highlights the advantage of controlled partial linker thermolysis to synthesize hierarchical MOFs to achieve the advanced single-site photocatalysis.

High Proton Conductivity of the UiO-66-NH2-SPES Composite Membrane Prepared by Covalent Cross-Linking

A sulfonated poly(ethersulfone) (SPES)-metal-organic framework (MOF) film with excellent proton conductivity was synthesized by anchoring UiO-66-NH₂ to the main chain of the aromatic polymer through the Hinsberg reaction. The chemical bond was formed between the amino group in MOFs and the -SO₂Cl group in chlorosulfonated poly(ethersulfones) to conduct protons in the proton channel of the membrane, making the membrane have excellent proton conductivity. UiO-66-NH₂ is successfully prepared as a result of the consistency of the experimental and simulated powder X-ray diffraction (PXRD) patterns of MOFs. The existence of absorption peaks of characteristic functional groups in Fourier transform infrared (FTIR) spectra proved the successful preparation of SPES, PES-SO₂Cl, and a composite film. The results of the AC impedance test indicate that the composite film with a 3% mass fraction has the best proton conductivity of 0.215 S·cm^-1, which is 6.2 times higher than that of the blended film without a chemical bond at 98% RH and 353 K. To our knowledge, there are rarely any reports on the preparation of a composite membrane by directly linking MOFs and the membrane matrix with chemical bonds. This work provides a good way to synthesize the highly conductive proton exchange film.

Confinement effect of ionic liquid: Improve of the extraction performance of parent metal organic framework for phthalates

In order to better identify the hazards of pollutants, developing the analytical methods that can sensitively detect and precisely monitor the content of trace pollutants has been the constant pursuit. In this paper, a new solid phase microextraction coating-ionic liquid/metal organic framework (IL/MOF) was obtained through the IL-induced strategy and used for the solid phase microextraction (SPME) process. IL was introduced into metal-organic framework (MOF) cage based on the anion of ionic liquid could interact strongly with the zirconium nodes of UiO-66-NH₂. The introduction of IL not only increased the stability of composite, the hydrophobicity of IL also changed the environment of MOF channel, providing the hydrophobic effect to the targets. The confinement effect of IL effectively improved the extraction performance of parent MOF and the extraction performance of synthesized IL/UiO-66-NH₂ for phthalates (PAEs) were 1.3-3.0 times that of parent UiO-66-NH₂. Thanks to the strong interaction force (hydrogen bonding interaction, π-π stacking, hydrophobic interaction force), the IL/UiO-66-NH₂-coated fiber coupled with gas chromatography-mass spectrometer showed a wide linear ranges (1-5000 ng L^-1) with good correlation (R², 0.9855-0.9987), lower detection limit (0.2-0.4 ng L^-1) and satisfactory recoveries (95.3-119.3%) for PAEs. This article is dedicated to provide another way to improve the extraction performance of material.

Constructing functional metal-organic frameworks by ligand design for environmental applications

Metal-organic frameworks (MOFs) with unique physical and chemical properties are composed of metal ions/clusters and organic ligands, including high porosity, large specific surface area, tunable structure and functionality, which have been widely used in chemical sensing, environmental remediation, and other fields. Organic ligands have a significant impact on the performance of MOFs. Selecting appropriate types, quantities and properties of ligands can well improve the overall performance of MOFs, which is one of the critical issues in the synthesis of MOFs. This article provides a comprehensive review of ligand design strategies for functional MOFs from the number of different types of organic ligands. Single-, dual- and multi-ligand design strategies are systematically presented. The latest advances of these functional MOFs in environmental applications, including pollutant sensing, pollutant separation, and pollutant degradation are further expounded. Furthermore, an outlook section of providing some insights on the future research problems and prospects of functional MOFs is highlighted with the purpose of conquering current restrictions by exploring more innovative approaches.

Carbon dioxide separation and capture by adsorption: a review

Rising adverse impact of climate change caused by anthropogenic activities is calling for advanced methods to reduce carbon dioxide emissions. Here, we review adsorption technologies for carbon dioxide capture with focus on materials, techniques, and processes, additive manufacturing, direct air capture, machine learning, life cycle assessment, commercialization and scale-up.

Molecular docking with SARS-CoV-2 and potential drug property of a bioactive novel Zn(II) polymer: A combined experimental and theoretical study

A new Zn(II) coordination polymer based on o-phthalato (Phth) and 2-aminopyridine (2-Ampy) viz. {[Zn(2-Ampy)2(Phth)]∙(H2O)]}n (1) has been synthesized at room temperature and characterized by elemental analyses, electronic spectroscopy, FT-IR spectroscopy, thermal analysis (TGA/DSC), powder X-ray diffraction (PXRD) and single crystal X-ray diffraction. The basic trimeric units of 1 form a polymeric chain by N-H⋯O and π⋯π interactions. These polymeric chains interconnect through various non-covalent interactions in two perpendicular directions to ultimately give rise to a 3D architecture of 1. The interesting non-covalent interactions in 1, contributing to its stability in the solid state are studied by Hirshfeld surface analysis and other different theoretical tools. Molecular docking study of 1 is performed against six different proteins of SARS-CoV-2. The drug potential of the synthesized compound is evaluated by ADMET calculations.

A Novel Aluminum-Based Metal-Organic Framework with Uniform Micropores for Trace BTEX Adsorption

Metal-organic frameworks (MOFs) are potential porous adsorbents for benzene, toluene, ethylbenzene and xylene (BTEX). A novel MOF, using low toxic aluminum (Al) as the metal, named as ZJU-620(Al), with uniform micropore size of 8.37±0.73 Å and specific surface area of 1347 m²  g^-1 , was synthesized. It is constructed by one-dimensional rod-shaped AlO₆ clusters, formate ligands and 4,4',4''-(2,4,6-trimethylbenzene-1,3,5-triyl) tribenzoic ligands. ZJU-620(Al) exhibits excellent chemical-thermal stability and adsorption for trace BTEX, e.g., benzene adsorption of 3.80 mmol g^-1 at P/P₀ =0.01 and 298 K, which is the largest one reported. Using Grand Canonical Monte Carlo simulations and Single-crystal X-ray diffraction analyses, it was observed that the excellent adsorption could be attributed to the high affinity of BTEX molecules in ZJU-620(Al) micropores because the kinetic diameters of BTEX are close up to the pore size of ZJU-620(Al).

Semi-hydrogenation of α,β-unsaturated aldehydes over sandwich-structured nanocatalysts prepared by phase transformation of thin-film Al2O3 to Al-TCPP

The semi-hydrogenation of α,β-unsaturated aldehydes to the desired unsaturated alcohols with both high conversion and high selectivity remains a big challenge. Herein, we designed a sandwich-structured nanocatalyst for the highly selective hydrogenation of various α,β-unsaturated aldehydes (e.g., cinnamaldehyde, furfural, crotonaldehyde, and 3-methyl-2-butenal) to the targeted unsaturated alcohols. Highly accessible platinum nanoparticles were sandwiched between a metal-organic framework (MOF) core (i.e., MIL-88B(Fe)) and a MOF shell (i.e., Al-TCPP). In particular, the growth of the Al-TCPP shell was achieved by atomic layer deposition (ALD) of thin-film Al₂O₃ followed by phase transformation with a tetrakis(4-carboxyphenyl)porphyrin (H₄TCPP) linker. The thickness of the Al-TCPP shell can be finely controlled by adjusting the cycle number of alumina ALD and the concentration of the H₄TCPP linker during the phase transformation of Al₂O₃ to Al-TCPP. It was proven that the permeable MOF shells could serve as selectivity regulators for the activation of the CO bonds in α,β-unsaturated aldehydes (in preference to the CC bonds), leading to higher selectivity towards unsaturated alcohols as compared to the conventional surface supported Pt catalysts. Mechanistic insights showed that the enhanced catalytic performance was attributed to (i) the modified electronic state of sandwiched Pt nanoparticles by the two MOF layers and (ii) the steric hindrance effect on substrate diffusion through the sandwich-structured catalysts.

Utilization of UiO-66-NH<sub>2</sub>@cellulose hybrid aerogel for solid-phase extraction of sildenafil in health products

研究建立了一种基于UiO-66-NH₂@纤维素复合气凝胶的高灵敏度固相萃取新方法,与高效液相色谱法联用用于保健品中西地那非的检测。先将纤维素进行醛基和酰肼基的功能化,然后将两种功能化的纤维素通过交联并负载UiO-66-NH₂形成复合气凝胶。将此复合气凝胶作为固相萃取的吸附剂使用时,易于收集且不需要外加磁场或者抽真空的辅助作用,操作简单。研究对制备所得的UiO-66-NH₂@纤维素复合气凝胶进行了X-射线粉末衍射、扫描电镜、红外光谱和N₂吸附等表征,结果显示UiO-66-NH₂成功负载于气凝胶的孔道中,纤维素气凝胶掺杂了UiO-66-NH₂之后其孔道结构变得规整,并且比表面积增大。研究优化了复合气凝胶中UiO-66-NH₂的负载量对萃取的影响,高比例的负载量有利于西地那非的富集,并且最高的负载率为50%。研究优化了影响西地那非富集效率的实验条件,包括溶液pH、萃取时间、洗脱剂类型、洗脱时间、洗脱体积和离子强度。采用安捷伦Zorbax Eclipse Plus C18色谱柱(150 mm×4.6 mm, 5 μm)进行分离,以含0.1 mol/L三乙胺的磷酸盐水溶液(pH=6.50)-乙腈(30∶70, v/v)为流动相进行洗脱,检测波长为292 nm。在最佳的萃取条件下(pH为9.0,萃取时间为60 min,洗脱剂为乙腈,洗脱液体积为3×2 mL,洗脱时间为40 min),该分析方法的线性范围为10~2000 ng/mL (相关系数R²=0.9949),检出限(LOD, S/N=3)为2.85 ng/mL,富集因子为59.17。将该方法用于保健品中西地那非的萃取,所得回收率为74.93%~89.12%,相对标准偏差为2.8%~5.3%,表明了方法的回收率和精密度良好,说明了该方法具有应用于保健品中西地那非日常检测的潜力。

Controllable Synthesis of 1, 3, 5-tris (1H-benzo[d]imidazole-2-yl) Benzene-Based MOFs

The growing interest in metal–organic frameworks (MOFs) in both industrial and scientific circles has increased in the last twenty years, owing to their crystallinity, structural versatility, and controlled porosity. In this study, we present three novel MOFs obtained from the 1, 3, 5-tris (1H-benzo[d]imidazole-2-yl) benzene (TIBM) organic linker. The formed TIBM crystal powders were characterized by scanning electron microscopy (SEM) to estimate the morphology of the particles, powder X-ray diffraction (XRD) to confirm the crystal structure, Brunauer–Emmett–Teller (BET) method for structural analysis, and thermogravimetric measurements to examine the thermal stability. The TIBM-Cu MOF showed excellent CO2 (3.60 mmol/g) adsorption capacity at 1 bar and 298 K, because of the open Cu site, compared to TIBM-Cr (1.6 mmol/g) and TIBM-Al (2.1 mmol/g). Additionally, due to the high porosity (0.3–1.5 nm), TIBM-Cu MOF showed a considerable CO2/N2 selectivity (53) compared to TIBM-Al (35) and TIBM-Cr (10).

Recyclable self-floating A-GUN-coated foam as effective visible-light-driven photocatalyst for inactivation of Microcystis aeruginosa

In this work, a recyclable self-floating A-GUN-coated (Ag/AgCl@g-C₃N₄@UIO-66(NH₂)-coated) foam was fabricated for effective inactivation of Microcystis aeruginosa (M. aeruginosa) under visible light. The floating photocatalyst was able to inactivate 98% of M. aeruginosa within 180 min under the visible-light irrigation, and the floating photocatalyst exhibited a stable performance in various conditions. Moreover, the inactivation efficiency can still maintain nearly 92% after five times recycle experiments, showing excellent photocatalytic stability. Furthermore, effects of A-GUN/SMF floating catalyst on the physiological properties, cellular organics, and algal functional groups of M. aeruginosa were studied. The floating photocatalyst can not only make full use of excellent photocatalytic activities of A-GUN nanocomposite, but also promote contact between catalyst and algae, and realize the effective recovery of the photocatalyst. Finally, possible photocatalytic inactivation mechanisms of algae were obtained, which provides references for removing cyanobacteria blooms in real water bodies.

Fabrication of heterostructured Ag/AgCl@g-C3N4@UIO-66(NH2) nanocomposite for efficient photocatalytic inactivation of Microcystis aeruginosa under visible light

In this work, a novel Ag/AgCl@g-C₃N₄@UIO-66(NH₂) heterojunction was constructed for photocatalytic inactivation of Microcystis aeruginosa (M. aeruginosa) under visible light. The photocatalyst was synthesized by a facile method and characterized by XRD, SEM, TEM, BET, XPS, FT-IR, UV-vis DRS, PL and EIS. The nanocomposite can not only provide lots of active sites, but also improve capacities to utilize visible-light energy and effectively transfer charge carriers, thus enhancing removal efficiencies of cyanobacteria (99.9% chlorophyll a was degraded within 180 min). Various factors in photodegradation of chlorophyll a were studied. Besides, changes on cellular morphologies, membrane permeability, physiological activities of M. aeruginosa during photocatalysis were investigated. Moreover, the cycle test indicated that Ag/AgCl@g-C₃N₄@UIO-66(NH₂) exhibits excellent reusability and photocatalytic stability. Finally, a possible mechanism of M. aeruginosa inactivation was proposed. In a word, Ag/AgCl@g-C₃N₄@UIO-66(NH₂) can efficiently inactivate cyanobacteria under visible light, thus providing useful references for further removal of harmful algae in real water bodies.

Dual-Emission Zr-MOF-Based Composite Material as a Fluorescence Turn-On Sensor for the Ultrasensitive Detection of Al3

In this work, a novel zirconium-based metal-organic framework (MOF) composite material, UiO-(OH)₂@RhB, has been solvothermally prepared with zirconyl chloride octahydrate, 2,5-dihydroxyterephthalic acid, and rhodamine B (RhB) for ratiometric fluorescence sensing of Al³⁺ ions in an aqueous medium. The luminescence measurement results showed that, at the single excitation wavelength of 420 nm, the fluorescence intensity of the ligand at 500 nm increased significantly in the case of Al³⁺, while that of RhB at 583 nm changed slightly, together with an apparent color change. Under optimal conditions, UiO-(OH)₂@RhB exhibited an extraordinary sensitivity (10 nM), good selectivity, and a fast response (2 min) for Al³⁺. As far as we know, the limit of detection is superior to that of the current reported MOF-based Al³⁺ fluorescence sensors. The response mechanism suggested that -OH could capture Al³⁺ in water through coordination and high electrostatic affinity and achieved turn-on ratiometric fluorescence through the excited-state intramolecular proton transfer process and stable fluorescence of RhB. In addition, this sensor was also applied to actual food samples (grain beans), with the recoveries ranging from 89.08% to 113.61%. Such a turn-on ratiometric fluorescence sensor will provide a constructive strategy for the ultrasensitive detection of Al³⁺ in practical applications.

Investigation of a modified metal-organic framework UiO-66 with nanoscale zero-valent iron for removal of uranium (VI) from aqueous solution

A novel composite material (nZVI/UiO-66) of nanoscale zero-valent iron (nZVI) with a functionalized metal-organic framework was synthesized by this study via a coprecipitation method, which was used for the efficient removal of U(VI) in the aqueous solution. The nZVI/UiO-66 had an excellent removal capacity of 404.86 mg g^-1 with an initial U(VI) concentration of 80 mg L^-1, 313 K and pH = 6. The transmission electron microscopy (TEM) revealed that nZVI particles were inhomogeneously distributed on the surface of UiO-66. The analysis by the X-ray diffraction (XRD) has further illustrated that the introduction of nZVI did not change the structure of UiO-66. The adsorption process closely followed the pseudo-second-order kinetic and the Freundlich isotherm model. The removal process of U(VI) by nZVI/UiO-66 was spontaneous and endothermic. Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses have illustrated that the mechanism was mainly related to adsorption of U(VI) from UiO-66 and reduction of U(VI) by nZVI. The Zr-O bonds were shown to play a vital role in the uranium removal. nZVI/UiO-66 could be recycled. The uptake rate could be maintained at around 80% after 5 cycles of use. Therefore, these results manifested that the nZVI/UiO-66 is a promising sorbent for the efficient and selective removal of U(VI) in radioactive wastewaters.

The Effect of Surface Hydroxylation on MOF Formation on ALD Metal Oxides: MOF-525 on TiO2/Polypropylene for Catalytic Hydrolysis of Chemical Warfare Agent Simulants

Metal-organic framework (MOF) fibrous composites were synthesized in a variety of methods in attempt to incorporate the highly effective reactivity of MOFs into a more facile and applicable format. Recent advances have demonstrated incorporating a metal oxide nucleation surface or reactive layer promotes conformal, well-adhered MOF growth on substrates. These materials have demonstrated promising reactivity in capturing or degrading chemical warfare agents and simulants. Here, we examine the mechanisms for MOF nucleation from metal oxide thin films to explore why some metal oxide sources are better suited for one synthesis mechanism over another. We isolate metal oxide extent of hydroxylation as an indicative factor as to whether the film serves as a nucleation promoter or may be converted directly to the MOF thin films. MOF-525 growth on Al₂O₃, TiO₂, and ZnO coated fibers is demonstrated to corroborate these findings and used to degrade chemical warfare agent simulant dimethyl-4-nitrophenyl phosphate.

Palladium Nanoclusters Confined in MOF@COP as a Novel Nanoreactor for Catalytic Hydrogenation

Metal-nanocluster-doped porous materials are attracting considerable research attention due to their specific catalytic performance. In this study, core-shell metal-organic frameworks@covalent organic polymer (MOF@COP) nanocomposites were formed by the covalent linking of chemically stable COP on the surface of size-selective UiO-66-NH₂. Pd nanoclusters with an average diameter of ∼0.8 nm were successfully confined in UiO-66-NH₂@COP, and the obtained nanoreactor, referred to as UiO-66-NH₂@COP@Pd, exhibited abundant porosity, high stability, and large surface area. Notably, the UiO-66-NH₂@COP@Pd nanoreactor exhibited superior catalytic activity and stability for the catalytic reduction of 4-nitrophenol and hydrogenation of other nitroarenes, demonstrating the potential of Pd-cluster-doped MOF@COP hybrid materials as candidates for efficient catalytic hydrogenation. This study may provide new avenues for the construction of MOF@COP-hybrid-material-based heterogeneous catalysts for efficient catalytic applications.

A hierarchical structured steel mesh decorated with metal organic framework/graphene oxide for high-efficient oil/water separation

A hierarchical structured steel mesh decorated with metal organic framework (UiO-66-NH₂) nanoparticles/graphene oxide (GO) nanosheets was successfully prepared via a simple self-assemble method. Because water molecules tend to build hydrogen bonds with the amine, carboxyl and hydroxyl functional groups of UiO-66-NH₂/GO hierarchical structure, the hierarchical structure can easily capture water and tightly lock the water to build a stable water layer on the steel mesh surface and block oil in contact with the steel mesh. Therefore, the obtained hierarchical structured steel mesh exhibits super-hydrophilicity, underwater super-oleophobicity, excellent oil resistance and outstanding oil/water separation performance with a superior high permeating flux (54,500 L m^-2  h^-1) and rejection (>99.9%) under gravity force, indicating the mesh possesses great potential for treating oily wastewater.

New development of atomic layer deposition: processes, methods and applications

Atomic layer deposition (ALD) is an ultra-thin film deposition technique that has found many applications owing to its distinct abilities. They include uniform deposition of conformal films with controllable thickness, even on complex three-dimensional surfaces, and can improve the efficiency of electronic devices. This technology has attracted significant interest both for fundamental understanding how the new functional materials can be synthesized by ALD and for numerous practical applications, particularly in advanced nanopatterning for microelectronics, energy storage systems, desalinations, catalysis and medical fields. This review introduces the progress made in ALD, both for computational and experimental methodologies, and provides an outlook of this emerging technology in comparison with other film deposition methods. It discusses experimental approaches and factors that affect the deposition and presents simulation methods, such as molecular dynamics and computational fluid dynamics, which help determine and predict effective ways to optimize ALD processes, hence enabling the reduction in cost, energy waste and adverse environmental impacts. Specific examples are chosen to illustrate the progress in ALD processes and applications that showed a considerable impact on other technologies.

A Zn(ii) metal–organic framework constructed by a mixed-ligand strategy for CO2 capture and gas separation

A microporous Zn(ii) metal–organic framework has been assembled using a mixed-ligand strategy, and it exhibits high capture ability for CO₂ and good selectivity for CO₂/CH₄, C₂H₆/CH₄ and C₃H₈/CH₄.

Chemical Protective Textiles of UiO-66-Integrated PVDF Composite Fibers with Rapid Heterogeneous Decontamination of Toxic Organophosphates

Metal-organic frameworks (MOFs) are a new and growing area of materials with high porosity and customizability. UiO-66, a zirconium-based MOF, has shown much interest to the military because of the ability of the MOF to catalytically decontaminate chemical warfare agents (CWAs). Unfortunately, the applications for MOFs are limited because of their powder form, which is difficult to incorporate into protective clothing. As a result, a new area of research has developed to functionalize fabrics with MOFs to make a wearable multifunctional fabric that retains the desired properties of the MOF. In this work, UiO-66 was incorporated into poly(vinylidene) fluoride/Ti(OH)₄ composite fabric using electrospinning and evaluated for its use in chemical protective clothing. The base triethanolamine (TEA) was added to the composite fabric to create a self-buffering system that would allow for catalytic decontamination of CWAs without the need for a buffer solution. The fabrics were tested against the simulants methyl-paraoxon (dimethyl (4-nitrophenyl) phosphate, DMNP), diisopropyl fluorophosphate (DFP), and the nerve agent soman (GD). The results show that all of the samples have high moisture vapor transport and filtration efficiency, which are desirable for protective clothing. The incorporation of TEA decreased air permeation of the fabric, but increased the catalytic activity of the composite fabric against DMNP and DFP. Samples with and without TEA have rapid half-lives ( t_1/2) as short as 35 min against GD agent. These new catalytically active self-buffering multifunctional fabrics have great potential for application in chemical protective clothings.

Toxic Organophosphate Hydrolysis Using Nanofiber-Templated UiO-66-NH2 Metal-Organic Framework Polycrystalline Cylinders

Metal organic frameworks (MOFs), the UiO series in particular, have attracted much attention because of the high surface area and ability to capture and decontaminate chemical warfare agents. Much work has been done on incorporating these MOFs into or onto textile materials while retaining the desirable properties of the MOF. Many different techniques have been explored to achieve this. Atomic layer deposition (ALD) of TiO₂ followed by solvothermal synthesis of MOF has become one of the most adaptable techniques for growing MOFs on the surface of many different polymer fabric materials. However, little work has been done with using this technique on polymer composite materials. In this work, UiO-66-NH₂ was grown onto the surface of poly(methyl methacrylate) (PMMA)/Ti(OH)₄ and poly(vinylidene fluoride) (PVDF)/Ti(OH)₄ composite fibers by first modifying the surface with ALD of TiO₂ (@TiO₂) followed by solvothermal synthesis of MOF (@MOF). The catalytic activity of these materials was then evaluated using the simulant paraoxon-methyl (DMNP). These new MOF-functionalized composite fabrics were compared to polyamide-6 (PA-6)@TiO₂@MOF- and polypropylene (PP)@TiO₂@MOF-functionalized fabrics. PMMA/Ti(OH)₄@TiO₂@MOF fibers resulted in unique hollowed fibers with high surface area of 264 m²/g and fast catalytic activity. The catalytic activity of these samples was found to be related to the active MOF mass fraction on the MOF-functionalized composite fabric, with the hollowed PMMA/Ti(OH)₄@TiO₂@MOF having the highest weight percent of active MOF and a DMNP t_1/2 of 26 min followed by PA-6@TiO₂@MOF with 45 min, PVDF/Ti(OH)₄@TiO₂@MOF with 61 min, and PP@TiO₂@MOF with 83 min.

Enhanced visible-light photocatalytic activity to volatile organic compounds degradation and deactivation resistance mechanism of titania confined inside a metal-organic framework

Poor visible-light-driven activity and deactivation property as well as wide band gap of the most common TiO₂ photocatalyst significantly limits its practical application in volatile organic compounds (VOCs) purification. In this study, tiny TiO₂ nanoparticles incorporated into a typical metal-organic framework (MOF), NH₂-UiO-66, with controllable TiO₂ content and size, were synthesized based on the hard-soft acid-base (HSAB) principle and applied to VOCs purification. Compared to bare TiO₂, the TiO₂@NH₂-UiO-66 composites could extend the optical absorption to the visible light range and accelerate the photogenerated electrons-holes separation, due to the excellent interface contact between TiO₂ and NH₂-UiO-66. Moreover, the abundant interconnected 3D cavities of the outer MOF allowed for VOCs to easily diffuse into the pores, producing a concentration microenvironment around the encapsulated TiO₂. The TiO₂@NH₂-UiO-66 composites exhibited a markedly improved photocatalytic efficiency and a good resistance to deactivation during the photocatalytic degradation of gaseous styrene under visible light illumination, which were associated with the synergetic effects between the TiO₂ and MOF. The TiO₂@NH₂-UiO-66 with 5 wt% TiO₂ could efficiently mineralize styrene to CO₂ to some extent companying with the removal ratio >99% within 600 min, whereas the removal efficiency over the bare TiO₂ only 32.5%.

Multifunctional Aromatic Carboxylic Acids as Versatile Building Blocks for Hydrothermal Design of Coordination Polymers

Selected recent examples of coordination polymers (CPs) or metal-organic frameworks (MOFs) constructed from different multifunctional carboxylic acids with phenyl-pyridine or biphenyl cores have been discussed. Despite being still little explored in crystal engineering research, such types of semi-rigid, thermally stable, multifunctional and versatile carboxylic acid building blocks have become very promising toward the hydrothermal synthesis of metal-organic architectures possessing distinct structural features, topologies, and functional properties. Thus, the main aim of this mini-review has been to motivate further research toward the synthesis and application of coordination polymers assembled from polycarboxylic acids with phenyl-pyridine or biphenyl cores. The importance of different reaction parameters and hydrothermal conditions on the generation and structural types of CPs or MOFs has also been highlighted. The influence of the type of main di- or tricarboxylate ligand, nature of metal node, stoichiometry and molar ratio of reagents, temperature, and presence of auxiliary ligands or templates has been showcased. Selected examples of highly porous or luminescent CPs, compounds with unusual magnetic properties, and frameworks for selective sensing applications have been described.

UiO-66-NH2 Metal-Organic Framework (MOF) Nucleation on TiO2, ZnO, and Al2O3 Atomic Layer Deposition-Treated Polymer Fibers: Role of Metal Oxide on MOF Growth and Catalytic Hydrolysis of Chemical Warfare Agent Simulants

Metal-organic frameworks (MOFs) chemically bound to polymeric microfibrous textiles show promising performance for many future applications. In particular, Zr-based UiO-66-family MOF-textiles have been shown to catalytically degrade highly toxic chemical warfare agents (CWAs), where favorable MOF/polymer bonding and adhesion are attained by placing a nanoscale metal-oxide layer on the polymer fiber preceding MOF growth. To date, however, the nucleation mechanism of Zr-based MOFs on different metal oxides and how product performance is affected are not well understood. Herein, we provide new insight into how different inorganic nucleation films (i.e., Al₂O₃, ZnO, or TiO₂) conformally coated on polypropylene (PP) nonwoven textiles via atomic layer deposition (ALD) influence the quality, overall surface area, and the fractional yield of UiO-66-NH₂ MOF crystals solvothermally grown on fiber substrates. Of the materials explored, we find that TiO₂ ALD layers lead to the most effective overall MOF/fiber adhesion, uniformity, and a rapid catalytic degradation rate for a CWA simulant, dimethyl p-nitrophenyl phosphate (DMNP) with t_1/2 = 15 min, 580-fold faster than the catalytic performance of untreated PP textiles. Interestingly, compared to ALD TiO₂ and Al₂O₃, ALD ZnO induces a larger MOF yield in solution and mass loading on PP fibrous mats. However, this larger MOF yield is ascribed to chemical instability of the ZnO layer under MOF formation condition, leading to Zn²⁺ ions that promote further homogeneous MOF growth. Insights presented here improve understanding of compatibility between active MOF materials and substrate surfaces, which we believe will help advanced MOF composite materials for a variety of useful functions.