Feasibility study of CAU-1 deposited on alumina hollow fiber for desalination applications

Ab Initio Molecular Dynamics Study of the Proton Transfer in Hydroxyl Ion-Induced Hydrolysis of Aluminum Monomers

The hydrolysis process of Al(H2O)63+ induced by hydroxyl ions (OH-) is significant to aluminum solution chemistry. Previous investigations of hydrolysis reactions have primarily relied on static calculations in an implicit solvent environment. Herein, we employ ab initio molecular dynamics (AIMD) to investigate the evolution process of Al(H2O)63+ under various local alkaline conditions in an explicit solvent environment. Our work demonstrates the effect of solvent water in hydrolysis reactions. Specifically, the stepwise hydrolysis reaction induced by hydroxyl ions involves water wire compression and concerted proton transfers. Dehydration reactions occur when the number of hydroxyl ligands attached to the aluminum ion (Al3+) equals or exceeds three. Moreover, the Al(H2O)n(OH)3 species exhibit unique hydrolysis and dehydration reaction characteristics compared to other species. The geometrically stable aluminum monomers determined by AIMD are Al(H2O)5(OH)12+, Al(H2O)4(OH)2+, Al(H2O)1(OH)3, and Al(OH)4-. In addition, the topological analysis analyzes the interaction between Al3+ and coordinated H2O in different configurations, indicating the weakest interaction appearing in Al(H2O)n(OH)3 species.

A Mini Review of Ceramic-Based MOF Membranes for Water Treatment

Ceramic membranes have been increasingly employed in water treatment owing to their merits such as high-stability, anti-oxidation, long lifespan and environmental friendliness. The application of ceramic membranes mainly focuses on microfiltration and ultrafiltration processes, and some precise separation can be achieved by introducing novel porous materials with superior selectivity. Recently, metal-organic frameworks (MOFs) have developed a wide spectrum of applications in the fields of the environment, energy, water treatment and gas separation due to the diversity and tunable advantages of metal clusters and organic ligands. Although the issue of water stability in MOF materials inhibits the development of MOF membranes in water treatment, researchers still overcome many obstacles to advance the application of MOF membranes in water treatment processes. To the best of our knowledge, there is still a lack of a reviews on the development process and prospects of ceramic-based MOF membranes for water treatment. Therefore, in this review, we mainly summarize the fabrication method for ceramic-based MOF membranes and their application in water treatment, such as water/salt separation, pollutant separation, heavy metal separation, etc. Following this, based on the high structural, thermal and chemical stability of ceramic substrates, and the high controllability of MOF materials, the superiority and insufficient use of ceramic-based MOF membranes in the field of water treatment are critically discussed.

Ultrasensitive Determination of Natural Flavonoid Rutin Using an Electrochemical Sensor Based on Metal-Organic Framework CAU-1/Acidified Carbon Nanotubes Composites

Rutin, a natural flavonol glycoside, is widely present in plants and foods, such as black tea and wheat tea. The antioxidant and anti-inflammatory effects of flavonoids are well known. In this study, a new electrochemical rutin sensor was developed using multiwalled carbon nanotubes/aluminum-based metal-organic frameworks (MWCNT/CAU-1) (CAU-1, a type of Al-MOF) as the electrode modification material. The suspension of multiwalled carbon tubes was dropped on the surface of the GCE electrode to make MWCNT/GCEs, and CAU-1 was then attached to the electrode surface by electrodeposition. MWCNTs and CAU-1 were characterized using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Due to the synergistic effect of CAU-1 and MWCNT-COOH, the prepared sensor showed an ultrasensitive electrochemical response to rutin. Under optimized conditions, the sensor showed a linear relationship between 1.0 × 10^-9~3.0 × 10^-6 M with a detection limit of 6.7 × 10^-10 M (S/N = 3). The sensor also showed satisfactory stability and accuracy in the detection of real samples.

Exploring novel heterojunctions based on the cerium metal-organic framework family and CAU-1, as dissimilar structures, for the sake of photocatalytic activity enhancement

Ce-based metal-organic frameworks (Ce-MOFs) are excellent photocatalysts due to their high efficiency in charge transportation. The integration of this family with CAU-1 (CAU standing for Christian-Albrechts-University), as a MOF benefiting from its ultra-high surface area, can remarkably enhance the properties of the structure. This research includes four new heterojunctions, namely CAU-1/Ce-BDC-NH2, CAU-1/Ce-UiO-66, CAU-1/Ce-MOF-808, and CAU-1/Ce-BDC, prepared by an innovative method, and several characterization techniques were employed to study the structural features of the frameworks. Their high surface area and low bandgap energy seemed appropriate for catalytic applications. Therefore, CAU-1/Ce-BDC was chosen for the photocatalytic removal of Cr(vi), a dangerous heavy metal, from aqueous systems. According to the results, a 96% reduction of Cr(vi) to Cr(iii) within 75 min was observed, and the catalyst retained its stability after four runs of reactions under acidic conditions.

Highly sensitive electrochemical detection of myricetin in food samples based on the enhancement effect of Al-MOFs

Microporous aluminum-based metal-organic frameworks (CAU-1) are used to develop a simple and sensitive electrochemical sensor for myricetin (MYR) based on a modified carbon paste electrode (CPE) for the first time. The morphologies and electrochemical properties of the as-synthesized CAU-1 are studied utilizing various analytical methods including scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, N₂ adsorption-desorption, and electrochemical impedance spectroscopy. In terms of electrochemical oxidation of MYR, CAU-1/CPE with its large number of active micropores and rapid electron transfer demonstrates superior performance compared to the bare CPE. Under optimized conditions, the calibration curve for MYR exhibits a linear range of 1.0-10 μg L^-1 and 10-1000 μg L^-1 with a detection limit of 0.50 μg L^-1. The developed CAU-1/CPE exhibits superior analytical characteristics, compared to previously reported electrochemical sensors for MYR detection. Furthermore, CAU-1/CPE is employed to determine MYR in Myrica bark samples, and the results are consistent with those obtained by high-performance liquid chromatography, demonstrating the excellent potential of CAU-1/CPE for the rapid analysis of MYR in complicated real samples.

Aluminum-based metal-organic frameworks (CAU-1) highly efficient UO22+ and TcO4- ions immobilization from aqueous solution

In this research, an Al-based metal-organic framework (MOFs), CAU-1 was prepared through complexation between 2-aminoterephthalic acid and Al (III) by solvothermal approach, and simple operation and cost-effective synthetic route. The objective was to immobilize the typical positive/negative radionuclide ions (UO₂²⁺/TcO₄^-) in aqueous solution. The synthesized CAU-1 was characterized by XRD, FT-IR, TGA, FESEM, TEM-SAED, pH_pzc, XPS and N₂ physisorption analysis. The structure of CAU-1 possessed excellent thermostability, rich functional groups (‒NH₂ and ‒OH groups), as well as large surface area (1636.3 m²/g) and the micropore volume (0.51 m³/g). Furthermore, batch experiments demonstrated that CAU-1 with superior adsorption capacity was 648.37 (UO₂²⁺) mg/g and 692.33 (ReO₄^-) mg/g calculating from Langmuir isotherm model, respectively. Thermodynamic investigation showed the adsorption process was endothermic and spontaneous. In addition, the adsorption mechanism of ReO₄^- ion onto CAU-1 could be electrostatic attraction and chelation effect, while for UO₂²⁺ ion, was mainly chelation effect induced by nitrogen-containing and oxygen-containing functional groups. Hence, the inexpensive and high-capacity CAU-1 could be considered as a practical material for sequestrations of radioactive pollutants from water environment.