Aqueous Room Temperature Synthesis Research Articles

Room temperature aqueous synthesis of defect-engineered MOF-801 membrane towards efficient nanofiltration

Room temperature (RT) aqueous preparation of MOF membranes is of significant interest in meeting the demands of sustainability. Nevertheless, there remains no report on RT aqueous synthesis of water-stable high-valence MOF membranes to date. In this study, we developed a one-step RT protocol for fabricating defect-engineered MOF-801 membrane in aqueous media. Owing to enhanced structural hydrophilicity and enlarged micropore size, water was enabled to diffuse through the membrane with higher permeation flux. Obtained membrane exhibited exceptional dye rejection rate (CR:99.75 %, MB:99.69 % and MG:99.41 %) and unprecedented water flux (CR:77.33 L m−2 h−1·bar−1, MB:71.43 L m−2 h−1·bar−1 and MG:81.28 L m−2 h−1·bar−1), which were superior to state-of-the-art 3D pure MOF membranes. Our protocol paves a promising way towards sustainable production of water-stable MOF membranes under mild conditions.

Room-temperature aqueous synthesis of MOF-808(Zr) for selective adsorption of dye mixtures

ZrIV-based metal–organic frameworks (MOFs) featuring distinguished water stability, large surface area, and intriguing functionalities have immense potential for practical usage. However, conventional MOF synthesis approaches generally require high reaction temperatures and organic solvents to initiate and template the nucleation and growth, hindering sustainable and cost-effective manufacturing and application of Zr-based MOFs. In this study, a scalable, room-temperature and aqueous synthesis of MOF-808—a Zr-MOF extensively explored as an adsorbent in both academic and industrial sectors—was reported. A rational use of water/formic acid (FA) as a green co-solvent enabled the formation of Zr6-cluster in an aqueous phase, thereby facilitating subsequent coordination with H3BTC to yield well-crystallized MOF-808. The effects of the water/FA volume ratio, the total solvent volume, and reaction time on the physicochemical properties of MOF-808 were studied. The optimized synthesis conditions (FA/water = 2.7:8.1, and reaction time = 24 h) resulted in the synthesis of MOF-808 with good hydrophilicity, excellent stability, high surface area, and weak positive charges. Moreover, this synthesis approach was successfully upscaled, yielding 11.5 g of MOF-808 at a magnification factor of 48. Notably, MOF-808-V10.8 exhibited an impressive adsorption capacity for Congo Red (ca. 1500 mg/g) and demonstrated selective fractionation of dye mixtures, suggesting their potential application in dye wastewater treatment. This methodology is expected to provide guidance for aqueous and scalable fabrication of Zr-MOFs towards water-related environmental applications.

Room temperature aqueous synthesis of Ce(IV)-MOFs with UiO-66 architecture and their photocatalytic decarboxylative oxygenation of arylacetic acids

Cerium(IV)-based metal-organic frameworks (MOFs) have gained a growing attention in both scientific and industrial spheres due to their unique potential in fields such as redox catalysis and photocatalysis. However, the synthetic pathways of Ce(IV)-MOFs are still extremely dominated by the conventional solvothermal conditions. Meanwhile, the research on photocatalysis of Ce(IV)-MOFs is still in its infancy, more experimental evidence is highly desirable to accelerate the development of this field. Here we present an innovative, widespread, green and sustainable synthetic route for nanocrystalline Ce(IV)-MOFs with the UiO-66 structure. Seven Ce-UiO-66-MOFs were successfully prepared at room temperature using water as the sole solvent in the presence of sodium acetate (NaAc). Furthermore, the photocatalytic activities of these Ce(IV)-MOFs for decarboxylative oxygenation of 4-fluorophenylacetic acid to give corresponding C–O bond-forming products 4-fluorobenzaldehyde and 4-fluorobenzyl alcohol under blue light-emitting diodes (LEDs) irradiation and air were studied. Control experiments revealed that Ce-UiO-66-BDC exhibited the optimized catalytic efficiency among these Ce(IV)-MOFs, and can be applied to various arylacetic acids.

Energy‐Efficient Synthesis and High Thermoelectric Performance of α‐Cu2−ySe1−xTex

The high-temperature phase of β-Cu2 Se always appears as the major phase for the reaction carried out using chemical solution methods. Here, a procedure was developed that could fabricate a single phase of α-Cu2 Se1-x Tex (x=0.02 and 0.04) by room-temperature aqueous synthesis using NaBH4 as reducing agent followed by cold pressing and sintering at 650 °C for 6 h in a flowing gas mixture of 20 % H2 and 80 % N2 . The energy-efficient synthesis carried out at room temperature abides by the 6th principle for green chemistry with less energy consumption. The reaction mechanism was studied, and evidence was provided of α-Cu2 Se being formed via the reaction between elemental Cu and Se atoms at room temperature. The resulting materials were characterized by powder X-ray diffraction, field-emission scanning electron microscopy, thermoelectric transport measurements, and Hall measurements. Cu1.96 Se0.96 Te0.04 had the highest power factor of 11 μW cm-1 K-2 at 818 K, and Cu2 Se0.96 Te0.04 had the maximum zT≥1.4 at T≥920 K among this series of materials.

Formation mechanism and antisite defects of scalable room-temperature aqueous synthesis of SnSe: Effects of the pH value on the reaction yield, mean crystallite size, chemical composition, and carrier concentration

A simple and scalable wet chemical method was adopted to synthesize a series of single-phase nanosized SnSe at room temperature with the solution controlled at various pH values. The lattice constants, chemical compositions, carrier concentration, bond length of bonded atoms, reaction yield, and antisite defects of resulting materials exhibit significant dependence on the pH values of the aqueous solution in the synthesis. Detailed studies on the formation mechanism of SnSe indicate that our approach involves the reaction between elemental Sn and Se, instead of the competitive precipitating reaction between Sn2+ and Se2−. The energetic elemental Se might be provided by polyselenide ions Sex2−. The reaction yield increases after treating SnSe with hydrochloric acid. According to both elemental analyses using electron probe microanalyzer and studies of extended x-ray absorption fine structure spectra, the Se vacancy is generated and is accompanied by formation of antisite defects by treating SnSe with hydrochloric acid.

Biosynthesis and characterization of multifunctional mixed oxides of ZnCr2O4/ZnCrO4 nanoparticulate from natural leaf extracts of Hibiscus Rosa Sinensis

Biological synthesis of zinc chromate mixed oxide nanoparticulate using natural leaf extracts of Hibiscus Rosa Sinensis. This is a simple, cost-effective and reproducible aqueous room temperature synthesis method to obtain spinel cubic phase ZnCr2O4 mixed oxide nanoparticles. X-ray diffraction (XRD) confirmed nanoparticles were crystalline with particle size estimated 14 nm for ZnCr2O4nanoparticles annealed at 700 °C, 26 nm at 500 °C, 56 nm at 200 °C and 70 nm at room temperature (RT). High resolution- transmission electron microscope (HR-TEM) and HR-scanning electron microscope (SEM) confirmed particles size of nanoparticles is around (fparticles) ∼14.5 ± 2 nm for HRTEM and 60–70 nm sized agglomerated cubic shaped particles for HRSEM. Fourier transform infrared spectrum (FTIR) was used for structural analysis. The band gaps calculated from UV–vis diffused reflectance (DR) are for ZnCr2O4mixed oxide nanoparticles at RT and annealed at 200 °C, 500 °C and 700 °C are 2.47 eV, 2.40 eV, 3.19 eV and 3.09 eV respectively. Fluorescence excitation was used to confirm band gaps of DR showing ZnCr2O4mixed oxide nanoparticles possess excellent photocatalytic activity.

Room temperature aqueous synthesis of UiO-66 derivatives via postsynthetic exchange.

Herein, we report the room temperature aqueous synthesis of the Zr(iv)-based metal-organic framework UiO-66 and a series of functionalized derivatives through postsynthetic exchange from a perfluorinated UiO-66-F4 precursor. All synthesized MOFs in this study were thoroughly characterized to verify formation of the desired MOF, porosity, crystallinity, and exchanged ligand content. This report represents a green, aqueous, room temperature synthesis of a highly valued series of Zr(iv)-based MOFs.

Revisiting the Growth Mechanism of Hierarchical Semiconductor Nanostructures: The Role of Secondary Nucleation in Branch Formation.

Although there have been advances in synthesizing hierarchical semiconductor materials, few studies have investigated the fundamental nucleation mechanisms to explain the origins of such complex structures. Resolving these nucleation and growth pathways is technically challenging but critical for developing predictive synthetic capabilities for the synthesis and application of new materials. In this Letter, we use state-of-the-art in situ liquid phase scanning electron microscopy (SEM) and high-resolution transmission electron microscopy in a combination with classical density functional theory (cDFT) to study the nucleation of highly branched wurtzite ZnO nanostructures via a facile, room-temperature aqueous synthesis route. Using a range of precursor concentrations, we systematically vary the hierarchical organizationof these nanostructures. In situ liquid phase SEM demonstrates that all branches form through secondary nucleation and grow by classical processes. Neither random aggregation nor oriented attachment is observed. cDFT results imply that the morphological evolution with increasing [Zn2+] arises from an interplay between a rising thermodynamic driving force, which promotes branch number and variability of orientation, and increasing barriers to interfacial transport due to ion correlation forces that alter the anisotropic kinetics of growth. These findings provide a quantitative picture of branching that sets to rest past controversies and advances efforts to decipher growth mechanisms of hierarchical structures in real solution environments.

MOF-derived Cu–C loaded with SnOx as a superior anode material for lithium-ion batteries

Cu–MOF was obtained by a facile aqueous room temperature synthesis method, and Cu–C was prepared by using Cu–MOF as a sacrificial template. The ultrafine SnOx nanoparticles were loaded onto Cu–C by a pyrolysis process to form SnOx/Cu–C. Cyclic voltammetry and galvanostatic charge/discharge were employed to examine the electrochemical properties of the as-synthesized composite. Benefiting from the excellent conductivity of Cu, the ultra-fine size of nanoparticles, the unique structure derived from MOF and the synergistic effect between SnOX and Cu–C, SnOX/Cu–C electrode exhibited an exceptional electrochemical property. A high charge specific capacity of 649 mA h g−1 can be reached even at a current density of 2000 mAg−1. The reversible capacity is maintained at 668 mA h g−1 at 1000 mA g−1 after 300 cycles. The results indicate that the material may be considered as a promising anode candidate for lithium-ion batteries.

Aqueous synthesis of highly monodisperse sub-100 nm AgCl nanospheres/cubes and their plasmonic nanomesh replicas as visible-light photocatalysts and single SERS probes

Despite the distinctive electrochemical and photocatalytic properties of nanostructured silver chloride (AgCl), the shape- and size-dependence of their properties have not been thoroughly investigated to date. The most substantial reason responsible for this incomplete study and the subsequent limited applications is the failure in controlling the structure of AgCl nanomaterials, mainly owing to the challenging synthetic conditions including organic phase and high reaction temperature. In this work, we reported a rapid one-pot room-temperature aqueous synthesis of highly monodisperse sub-100 nm AgCl nanomaterials with various shapes and sizes by controlling the precursor (Ag+ and AuCl4−) ratios. The remaining unreacted metal precursors (Ag+ and AuCl4−) used to produce AgClNC were subsequently reduced by ascorbic acid on the surface of the synthesized AgCl nanomaterials to form Ag/Au bimetallic nanomesh structures (AgClNC#AuAgCMs and SMs). After the removal of the AgCl nanotemplates, only nanomesh structures (AuAgCMs and SMs) were obtained. Importantly, we successfully decreased the size of the AgCl nanomaterials which were replicated into bimetallic spherical and cubic nanomesh structures that were small enough (∼100 nm) to show intense surface-plasmon-absorption bands. Based on these unique chemical and physical properties, we could take advantage of the plasmonic photocatalysis properties of the complex comprising semiconducting AgCl/metallic nanomesh replica for the complete removal of the environmentally harmful Cr6+ in the presence of sacrificial agents such as formic acid. Finally, the novel bimetallic nanomesh structures proved themselves to exhibit intense surface-enhanced Raman scattering properties in a single-particle enhancing the electromagnetic field.

Structural transition from two-dimensional ZIF-L to three-dimensional ZIF-8 nanoparticles in aqueous room temperature synthesis with improved CO2 adsorption

A new micron-sized leaf- two-dimensional (2D) structured zeolitic imidazolate framework (ZIF-L) and nano-sized ZIF-8 were successfully synthesised in aqueous basic solution at room temperature with the same molar ratio of reagents (Zn+2/Hmim=8). Both ZIFs have attracted tremendous research interest due to their wide applications including absorption, separation, and catalysis. This phase and morphology change could be tailored by changing the concentration of base-type additive triethylamine (TEA). Also, this morphology change from 2D (ZIF-L) to three-dimensional (3D) (ZIF-8) was observed by X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), attenuated total reflectance infrared (ATR-IR) spectroscopy analysis, and surface area and pore textural properties using micromeritics gas adsorption analyser. The total amount of basic sites and carbon dioxide (CO2) desorption capacity were also calculated using CO2 temperature-programmed desorption (CO2-TPD) technique. Furthermore, TEA/total mole ratio of 0.0006 was proved as transition loading between two phases. Also, the particle and crystal size of samples decreased with increasing TEA/total mole ratio. The smallest ZIF-L and ZIF-8 particles obtained were 1.6μm and 177nm, respectively that showed excellent thermal stability. The basicity and uptakes of CO2 improved proportionally with TEA and followed this order: ZIF-8>ZIF-L. This study provides some new insights into zeolitic imidazolate framework by controlling crystal growth and morphology.

Synthesis of Gold Nanoparticle-Embedded Silver Cubic Mesh Nanostructures Using AgCl Nanocubes for Plasmonic Photocatalysis.

A novel room-temperature aqueous synthesis for gold nanoparticle-embedded silver cubic mesh nanostructures using AgCl templates via a template-assisted coreduction method is developed. The cubic AgCl templates are coreduced in the presence of AuCl4- and Ag+ , resulting in the reduction of AuCl4- into gold nanoparticles on the outer region of AgCl templates, followed by the reduction of AgCl and Ag+ into silver cubic mesh nanostructures. Removal of the template clearly demonstrates the delicately designed silver mesh nanostructures embedded with gold nanoparticles. The synthetic mechanism, structural properties, and surface functionalization are spectroscopically investigated. The plasmonic photocatalysis of the cubic mesh nanostructures for the degradation of organic pollutants and removal of highly toxic metal ions is investigated; the photocatalytic activity of the cubic mesh nanostructures is superior to those of conventional TiO2 catalysts and they are catalytically functional even in natural water, owing to their high surface area and excellent chemical stability. The synthetic development presented in this study can be exploited for the highly elaborate, yet, facile design of nanomaterials with outstanding properties.

Large-scale room-temperature aqueous synthesis of Co superstructures with controlled morphology, and their application to electromagnetic wave absorption

In this work, we report on the large-scale room-temperature synthesis of Co superstructures using a facile liquid phase reduction method in an aqueous medium. This method yielded pure Co powders within a short period of time without the use of any surfactants. The morphological changes in the Co superstructures could be controlled simply by varying the amounts of reducing agent (hydrazine hydrate). The morphology of the Co powders systematically controlled from aggregated foliage to isolated microfoliage by increasing the hydrazine hydrate addition from 4 ml to 8 ml. The morphology-dependent electromagnetic properties, including the electric permittivity, and magnetic permeability, were investigated over the microwave frequency range, 2-18 GHz. Co isolated microfoliage showed a maximum reflection loss (RL) of -32 dB at 9 GHz with a matching thickness of 2.5 mm, whereas the aggregated foliage Co superstructures displayed a maximum RL of -17 dB at 11 GHz with a matching thickness of 2.5 mm. The stronger absorption for isolated microfoliage was ascribed to a continuous micro networks and vibrating microcurrent dissipation arise from size and shape of the isolated microfoliage. The calculated RL suggested that the as-prepared samples were potential microwave absorption candidates in the X-band region.

Shape design of cerium oxide nanoparticles for enhancement of enzyme mimetic activity in therapeutic applications

Cerium oxide nanoparticles (CONPs), widely used in catalytic applications owing to their robust redox reaction, are now being considered in therapeutic applications based on their enzyme mimetic properties such as catalase and super oxide dismutase (SOD) mimetic activities. In therapeutic applications, the emerging demand for CONPs with low cytotoxicity, high cost efficiency, and high enzyme mimetic capability necessitates the exploration of alternative synthesis and effective material design. This study presents a room temperature aqueous synthesis for low-cost production of shape-selective CONPs without potentially harmful organic substances, and additionally, investigates cell viability and catalase and SOD mimetic activities. This synthesis, at room temperature, produced CONPs with particular planes: {111}/{100} nanopolyhedra, {100} nano/submicron cubes, and {111}/{100} nanorods that grew in [110] longitudinal direction. Enzymatic activity assays indicated that nanopolyhedra with a high concentration of Ce4+ ions promoted catalase mimetic activity, while nanocubes and nanorods with high Ce3+ ion concentrations enhanced SOD mimetic activity. This is the first study indicating that shape and facet configuration design of CONPs, coupled with the retention of dominant, specific Ce valence states, potentiates enzyme mimetic activities. These findings may be utilized for CONP design aimed at enhancing enzyme mimetic activities in therapeutic applications.

Room temperature aqueous synthesis of BiVO4/NaBiO3 heterojunction with high efficiency for sulfadiazine removal

A novel BiVO4/NaBiO3 composite catalyst was firstly prepared in room-temperature aqueous, which was a facile and controlled synthesis approach. The as-prepared BiVO4/NaBiO3 composite samples exhibited excellent photocatalytic activity and recyclability for sulfadiazine degradation under xenon light irradiation. The photocatalytic mechanism was discussed based on the reactive species analysis.

Seeding-free aqueous synthesis of zeolitic imidazolate framework-8 membranes: How to trigger preferential heterogeneous nucleation and membrane growth in aqueous rapid reaction solution

Zeolitic imidazolate frameworks (ZIFs) have received attention for membrane separation applications due to their zeolite-like permanent porosity and tunable uniformly-sized micropores. Although aqueous room temperature synthesis has apparently opened up environmental friendly and efficient ways to synthesize ZIFs, it poses challenges for membrane preparation including unavoidable homogeneous nucleation. Many ZIF membranes prepared in an aqueous system are based on conventional secondary seeded growth techniques for zeolite membranes in spite of well-recognizing that the coordination chemistry of ZIFs is fundamentally different from the covalent chemistry of zeolites. In this study, we first applied a support-surface activation approach to promote heterogeneous nucleation followed by crystal growth in the aqueous system. Continuous well-intergrown ZIF-8 membranes were successfully grown on α-alumina porous support using zinc acetate and showed relatively-high hydrogen permeance of 6.9×10−7mol/m2sPa with corresponding ideal separation selectivity of 13.6 for the hydrogen/methane. The competitive interaction between the coordination of constructing framework and zinc–acetate interaction by carboxylate functionality of acetate anions is essential to control heterogeneous nucleation and membrane growth. Avoiding the seeding process and reducing the use of organic solvents can provide potential for improving a reproducible, scalable, and commercializable process configuration for membrane preparation.

Aqueous room temperature synthesis of zeolitic imidazole framework 8 (ZIF-8) with various concentrations of triethylamine

The schematic illustration shows the influence of triethylamine (TEA) concentration on ZIF-8 formation.

Synthesis of high-quality selenide/telluride nanocrystals from green precursors

As important inorganic semiconductor materials, selenide/telluride nanocrystals have shown great prospects in many areas, such as solar cells, light-emitting diodes, bio-labeling, photothermal therapy and so forth. With the establishment and development of the concepts of chemistry and nanoscience, people not only pursuit in the diversities of types, synthesis methods and functions of the nanocrystals, but also concentrate on whether the synthesis process itself is environmentally friendly at the same time. Here, with precursor preparation as the main line, we overview the development of green synthesis methods of selenide/telluride nanocrystals and highlight the oil phase phosphine-free and room-temperature aqueous synthesis methods. We hope this paper will provide a better consideration of the current problem and innovation in green synthesis of selenide/telluride nanocrystals.

A versatile, industrially relevant, aqueous room temperature synthesis of HKUST-1 with high space-time yield

A facile aqueous room temperature synthesis method has been developed to synthesize HKUST-1 from nano-materials to micro- and hierarchical porous structures by tuning either the copper source or the reaction time. The synthesis is readily scalable, with space-time yield >2000 kg m−3 day−1.

Morphology control of nickel oxalate by soft chemistry and conversion to nickel oxide for application in photocatalysis

The present work provides an effective methodology for controlled room-temperature aqueous synthesis of nickel oxalate (NiOX) nanosheets and nanoflakes in the presence of anion rich self-assembled bilayers of catanionic surfactant comprising of anionic sodium dodecyl sulfate (SDS) and cationic cetyltrimethylammonium bromide (CTAB). Encouragingly alteration of the CTAB/SDS ratio played an extraordinary role to form nanoflakes and nanosheets of NiOX. Our synthetic approach is combined with calcination to produce antiferromagnetic spherical and hexagonal nickel oxide (NiO) nanoparticles (NPs) as the end product. Synthesized nanostructured NiOX and NiO were characterized by X-ray diffraction study (XRD), energy dispersive X-ray spectroscopy (EDS), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). TEM studies illustrated that spherical NiO NPs have an average size around 5–10 nm and that of hexagonal NiO NPs have average width of about 22–27 nm. Temperature and field dependent magnetic properties of spherical and hexagonal NiO nanomaterials (NMs) were measured by using a SQUID magnetometer which revealed canted antiferromagnetic and spin glass nature, respectively. In addition, we report photocatalytic activity of NiO NMs, investigated on the photodegradation of phenol under ambient conditions, and as expected, the NiO having largest surface area showed best catalytic efficiency. This biomimetic catanionic surfactant inspired approach which require only metal ions as reactants have a definite potential towards an alternative, simple way of synthesizing metal oxide NMs.