Rapid synthesis of cerium-UiO-66 MOF nanoparticles for photocatalytic dye degradation

An unprecedented synthesis method is used to form a series of Ce-UiO-66-X (X = NH2, OH, H, NO2, COOH) metal–organic frameworks by precipitation from mixed solvents, with instantaneous crystallisation on combining separate solutions of ligands and metal precursors. This allows the first direct synthesis of Ce-UiO-66-OH. Powder X-ray diffraction (PXRD) shows that all materials are pure phase with a broadened profile that indicates nano-scale crystallite domain size. The effect of different functional groups on the benzene-1,4-dicarboxylate linker within the UiO-66 structure has been investigated on degradation of two cationic (methylene blue and rhodamine B) and two anionic (Congo red, and Alizarin red S) dyes under UV and visible light irradiation at room temperature. Analysis of the dye adsorption in the absence of light is accounted for using pseudo-first order kinetics, and the Ce-UiO-66-NH2, Ce-UiO-66-OH, and Ce-UiO-66-H materials display a considerable photocatalytic activity to degrade Alizarin red S and Congo red rapidly between 1 and 3 minutes. The materials show excellent photostability and recyclability under UV and visible light, with no loss of crystallinity seen by PXRD and activity maintained over 5 cycles, with 16 hours photostability for Ce-UiO-66-NH2

The use of unconventional methods to synthesise MOFs and MTV-MOFs for photocatalysis

This study introduces a novel rapid precipitation technique for synthesising metal-organic frameworks (MOFs) and multivariate MOFs (MTV-MOFs) in aqueous solutions, yielding high-quality, and crystallinity in MOFs and MTV-MOFs. A series of Ce-UiO-66-X (X = NH2, OH, H, NO2, COOH) and Ce/Zr-UiO-66(1,4-NDC/BDC), Ce/Zr-UiO-66(1,4-NDC/2,6-NDC), Ce/Zr-UiO-66(1,4-NDC), Ce/Ti-UiO-66(1,4-NDC), and Ce/Ti-UiO-66(NH2) were synthesised, with Ce-UiO-66-OH and all MTV-MOFs presented for the first time. The research mainly delves into synthesising bimetallic UiO-66 derivatives, with varying ratios of Ce to Zr and different linker types, aiming to understand the potential structural modifications. The efficacy of rapid precipitation, microwave, and ultrasonic methods over traditional solvothermal approaches was investigated to explore controling the molar ratio of metals in the bimetallic structures. The unconventional methods yield pure samples of mixed-metal materials with various concentrations, as confirmed by Pawley refinement against powder X ray diffraction (PXRD) and X-ray fluorescence spectroscopy (XRF). The effect of defects is investigated using thermogravimetric analysis (TGA), which reveals similar defect production at lower Ce concentrations. The microwave and rapid precipitation methods can produce non defective structures, specifically for Ce/Zr-UiO-66(1,4-NDC) and Ce/Zr-UiO-66(BDC). Synthesising MOFs by rapid precipitation gives materials with larger unit cell parameters than have been presented so far, which may be due to small crystal domain size and defective structure. Regarding the photocatalytic activities of the synthesised porous materials, Ce-UiO 66-NH2, Ce-UiO-66-OH, and Ce-UiO-66-H show significant photocatalytic activities to decolourise Alizarin Red S and Congo red within 1 to 3 minutes with 6 W/254 nm radiation. All MTV-MOFs, except Ce/Zr-UiO-66(1,4-NDC/BDC), show the highest decolourisation activity, observed between 1 and 15 minutes in four different dyes. The materials demonstrate excellent photostability and recyclability under UV and visible light over 5 cycles of use, with no loss of crystallinity observed through PXRD. All MTV-MOFs and Ce-UiO-66-NH2 are stable under UV irradiation between 16 and 17 hours, respectively

Data for "Rapid Synthesis of Cerium-UiO-66 MOF Nanoparticles for Photocatalytic Dye Degradation"

An unprecedented synthesis method is used to form a series of Ce-UiO-66-X (X=NH2, OH, H, NO2, COOH) metal-organic frameworks by precipitation from mixed solvents, with instantaneous crystallisation on combining separate solutions of ligands and metal precursors. This allows the first direct synthesis of Ce-UiO-66-OH. Powder X-ray diffraction (PXRD) shows that all materials are pure phase with a broadened profile that indicates nano-scale crystallite domain size. The effect of different functional groups on the benzene-1,4-dicarboxylate linker within the UiO-66 structure has been investigated on degradation of two cationic (methylene blue and rhodamine B) and two anionic (Congo red), and Alizarin Red S) dyes under UV and visible light irradiation at room temperature. Analysis of the dye adsorption in the absence of light is accounted for using pseudo-first order kinetics, and the Ce-UiO-66-NH2, Ce-UiO-66-OH, and Ce-UiO-66-H materials display a considerable photocatalytic activity to degrade Alizarin Red S and Congo red rapidly between 1 and 3 minutes. The materials show excellent photostability and recyclability under UV and visible light, with no loss of crystallinity seen by PXRD and activity maintained over 5 cycles, with 16 hours photostability for Ce-UiO-66-NH2

Adsorption properties of tetracycline onto graphene oxide: equilibrium, kinetic and thermodynamic studies.

Graphene oxide (GO) nanoparticle is a high potential effective absorbent. Tetracycline (TC) is a broad-spectrum antibiotic produced, indicated for use against many bacterial infections. In the present research, a systematic study of the adsorption and release process of tetracycline on GO was performed by varying pH, sorption time and temperature. The results of our studies showed that tetracycline strongly loads on the GO surface via π-π interaction and cation-π bonding. Investigation of TC adsorption kinetics showed that the equilibrium was reached within 15 min following the pseudo-second-order model with observed rate constants of k2 = 0.2742-0.5362 g/mg min (at different temperatures). The sorption data has interpreted by the Langmuir model with the maximum adsorption of 323 mg/g (298 K). The mean energy of adsorption was determined 1.83 kJ/mol (298 K) based on the Dubinin-Radushkevich (D-R) adsorption isotherm. Moreover, the thermodynamic parameters such as ΔH°, ΔS° and ΔG° values for the adsorption were estimated which indicated the endothermic and spontaneous nature of the sorption process. The electrochemistry approved an ideal reaction for the adsorption under electrodic process. Simulation of GO and TC was done by LAMMPS. Force studies in z direction showed that tetracycline comes close to GO sheet by C8 direction. Then it goes far and turns and again comes close from amine group to the GO sheet

The UV–Vis absorption spectra of free TC, free GO and TC after adsorption on GO (GO-TC).

<p>The UV–Vis absorption spectra of free TC, free GO and TC after adsorption on GO (GO-TC).</p

The pseudo-first-order (a) and the pseudo-second-order (b) kinetics model for adsorption of tetracycline on GO suspension (20.0 mg/L), pH = 3.6, T = 298, 308, 318 K.

<p>The pseudo-first-order (a) and the pseudo-second-order (b) kinetics model for adsorption of tetracycline on GO suspension (20.0 mg/L), pH = 3.6, T = 298, 308, 318 K.</p

Structure of graphene oxide (a), Structure of tetracycline and pKa values (b).

<p>Structure of graphene oxide (a), Structure of tetracycline and pKa values (b).</p

Langmuir, Freundlich and D–R constants and correlation coefficients of TC adsorption on GO at different temperatures.

*<p>Dubinin–Radushkevich.</p

FTIR spectra of free TC, free GO and TC after adsorption on GO (GO-TC).

<p>FTIR spectra of free TC, free GO and TC after adsorption on GO (GO-TC).</p

Variation of z and x <i>vs</i>. time.

<p>Variation of z and x <i>vs</i>. time.</p