Functionalized Mn(II)-MOF based on host-guest interaction for selective and rapid capture of Congo red from water

Active metals decorated NiCo2O4 yolk-shell nanospheres as nanoreactors for catalytic reduction of nitroarenes and azo dyes

Transition-metal oxides (TMOs) have received a great deal of research attention and have been widely used in a variety of fields. However, conventional TMOs do not possess high specific surface area, sufficient active site on their surfaces, and limited their applications in catalysis. This study presents a two-step method for synthesizing active metal (M) decorated NiCo2O4 (M/NiCo2O4, M = Pd or Cu) nanospheres with yolk-shell nanostructures. Taking advantage of the unique morphology and the combination of dual active components (i.e., active NiCo2O4 substrate and decorated active metal), the as-prepared M/NiCo2O4 yolk-shell nanospheres can be employed as nanoreactors in the organic reactions. In catalyzing the reduction of a representative nitroarene (i.e., 4-NP) by NaBH4, the Pd/NiCo2O4 nanoreactors exhibit a superior catalytic efficiency to their counterparts (Cu/NiCo2O4 and NiCo2O4). The turnover frequency is much higher than that of various TMOs supported nanocatalysts have been reported over the past five years. Furthermore, the Pd/NiCo2O4 nanoreactors show excellent stability and common applicability of the reduction of various substituted nitrobenzenes and azo dyes. This work provides new rational design concept and preparation strategy for efficient nanoreactors with dual active components and sheds light on the practical application of chemical reactions.

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.

Synthesis and Characterization Bimetallic Organic Framework CoxFex(BDC) and Adsorption Cationic and Anionic Dyes

Co-doped Fe-MOF bimetallic organic framework materials at different ratios were synthesized based on the solvothermal method, and we evaluated their morphological characteristics by modern analytical methods such as SEM, XRD, FT-IR, and isotherm of nitrogen adsorption-desorption (BET). The specific surface area of the 0.3 CoFe-MOF sample (280.9 m2/g) is much larger than the Fe-MOF and samples at other ratios. The post-synthesized materials were evaluated for their ability to absorb various dyes, including Methylene Blue (MB), Methyl orange (MO), Congo red (CR), and Rhodamine (RhB), and evaluated for the effects of pH, the initial concentration of the dye solution, time, and dose of adsorbent. The results show that the 0.3 CoFe-MOF material has a high adsorption capacity that is superior to both the original Fe-MOF and the CoFe-MOFs at other ratios. The highest adsorption capacity of MB dye by 0.3 CoFe-MOF reaches up to 562.1 mg/g at pH 10, the initial concentration of MB of 200 mg/L, after 90 min. The charged properties of the dyes and the charged nature of the bimetallic organic frameworks are best demonstrated through the adsorption of dye mixtures. The adsorption efficiency on the mixed system of cationic (MB) and anionic (MO) dyes yielded the highest removal efficiency of 70% and 81%, respectively, after 30 min. Therefore, the research has opened up the potential application of M/Fe-MOF modified materials and CoFe-MOF in organic dyes adsorption in wastewater treatment for environmental protection.

Recent advances in metal-organic frameworks as adsorbent materials for hazardous dye molecules

Water is vital for the sustenance of all forms of life. Hence, water pollution is a universal crisis for the survival for all forms of life and a hurdle in sustainable development. Textile industry is one of the anthropogenic activities that severely pollutes water bodies. Inefficient dyeing processes result in thousands of tons of synthetic dyes being dumped in water bodies every year. Therefore, the efficient removal of synthetic dyes from wastewater has become a challenging research field. Owing to their tuneable structure-property aspects, metal-organic frameworks (MOFs) have emerged as promising adsorbents for the adsorptive removal of dyes from wastewater and textile effluents. In this perspective, we highlight recent studies involving the application of MOFs for the adsorptive removal of hazardous dye molecules. We also classify the developed MOFs into cationic, anionic, and neutral framework categories to comprehend their suitability for the removal of a given class of dyes.

Triggering Lewis Acidic Nature through the Variation of Coordination Environment of Cd-Centers in 2D-Coordination Polymers

The rational design and successful synthesis of novel functional metal-organic frameworks relies on careful selection of metals and versatile organic ligands. A newly designed pyrazole-based dicarboxylate ligand, 5-(3,5-dimethyl-1H-pyrazol-1-yl) 1,3-benzenedicarboxylic acid (H₂L), was utilized to obtain two new Cd-based coordination polymers I [Cd(L)(H₂O)]·H₂O and II [Cd(L)] under similar reaction conditions via solvothermal strategy. Single-crystal X-ray data confirmed that compound I exhibits a two-dimensional (2D) skeleton comprising pentagonal bipyramidal Cd-ions and an organic ligand moiety. Compound II has also formed a two-dimensional layer arrangement with the connectivity between trigonal bipyramidal Cd-ions and the organic ligand. Topological analysis revealed that compound I has formed unique 4³.6³ net topology while compound II has displayed a 4⁴.6² sql net topology with 2D frameworks. The Lewis acidic nature of both I and II containing a Cd²⁺ metal center has been correlated with the coordination number through dye adsorption-desorption and catalysis studies. The selective adsorption of anionic dye and the extent of adsorption are interrelated with the Cd-ion geometry. For the first time, the role of coordinated water molecule has been analyzed through heterogeneous catalysis reaction (i.e., cyanosilylation) with Cd-based 2D-coordination polymers (CPs). The plausible mechanisms have been proposed to explain the subsequent role of coordination number and environment in CPs.

Multifunctional polymers with interpenetrating structures: luminescence sensing, ECL behaviors, selective detection of Fe3+ ion and rapid removal of anionic dyes

Three unprecedented metal–organic frameworks with interspersed structures have been synthesized and structurally characterized.

A cationic [Ag12S12] cluster-based 2D coordination polymer and its dye composite with enhanced photocurrent and dielectric responses

A cationic cluster-based 2D coordination polymer captures Congo Red to form a composite with improved photocurrent and dielectric responses.