Ternary metal oxide embedded carbon derived from metal organic frameworks for adsorption of methylene blue and acid red 73

Metal-organic framework-derived metal oxides for resistive gas sensing: a review

Gas sensors with exceptional sensitivity and selectivity are vital in the real-time surveillance of noxious and harmful gases. Despite this, traditional gas sensing materials still face a number of challenges, such as poor selectivity, insufficient detection limits, and short lifespan. Metal oxides, which are derived from metal-organic framework materials (MOFs), have been widely used in the field of gas sensors because they have a high surface area and large pore volume. Incorporating metal oxides derived from MOFs into gas sensors can improve their sensitivity and selectivity, thus opening up new possibilities for the development of innovative, high-performance gas sensors. This article examines the gas sensing process of metal oxide semiconductors (MOS), evaluates the advances made in the research of different structures of MOF-derived metal oxides in resistive gas sensors, and provides information on their potential applications and future advancements.

Magnetic Fe3O4/bamboo-based activated carbon/UiO-66 composite as an environmentally friendly and effective adsorbent for removal of Bisphenol A

The magnetic Fe3O4/bamboo-based activated carbon/Zr-based metal-organic frameworks composite (Fe3O4/BAC/UiO-66) was prepared by hydrothermal method. The as-prepared material was analyzed via TEM, XRD, FT-IR, BET-BJH, VSM and XPS techniques, the results showed that it had good dispersion and magnetic separation capacity (Ms = 44.06 emu∙g-1). Then, the adsorption properties of materials for bisphenol A (BPA) were studied. The results revealed that the removal efficiency of 50 mg·L-1 BPA by 0.1 g of adsorbent can reach 87.18-95% in a wide pH range. Langmuir isotherm model and pseudo-second-order kinetic well fitted the adsorption data. The thermodynamic data indicated that the adsorption process was spontaneous and endothermic. Moreover, BAC as a supporter and UiO-66 as the functional part in the ternary composite may have a synergistic effect, which was beneficial for the removal of contaminants. The Fe3O4/BAC/UiO-66 can be simply separated from the water using its strong magnetism after finish adsorption process, which effectively avoids secondary contamination.

Fabrication of bimetallic-doped materials derived from a Cu-based complex for enhanced dye adsorption and iodine capture

In this work, we used Cu(II) ions, a bis-pyridyl-bis-amide ligand [N,N'-bis(4-pyridinecarboxamide)-1,2-cyclohexane (4-bpah)], and an aromatic dicarboxylic acid [1,4-cyclohexanedicarboxylic acid (H2CHDA)] to construct a 1D binuclear Cu-based complex, namely {[Cu3(4-bpah)(CHDA)3(H2O)]·2H2O}n (1). Moreover, we also developed a facile method to synthesize two monometallic/bimetallic-doped materials which were derived from the Cu complex (C-N-1 and C-V-1, which were doped with nitrogen and vanadium, respectively). The as-synthesized derived materials were fully characterized and the iodine sorption/release capabilities were investigated in detail. We performed iodine adsorption experiments on the two monometallic/bimetallic-doped materials and found that C-N-1 and C-V-1 possess highly efficient adsorption activities for the adsorption of iodine from solution. The C-N-1 and C-V-1 complexes exhibited remarkable adsorption capacities of 1141.60 and 1170.70 mg g-1, respectively, for iodine from a cyclohexane solution. Moreover, the dye adsorption properties of C-N-1 and C-V-1 were also investigated in detail. The obtained C-N-1 and C-V-1 exhibit effective dye uptake performances in water solution. The adsorption of Congo red (CR) on a single metal carbon material C-N-1 doped with heteroatoms reached equilibrium within 240 min and reached an adsorption capacity of 1357.00 mg g-1 and the adsorption capacities of C-V-1 for methylene blue (MB), gentian violet (GV), rhodamine B (RhB), and CR at room temperature were found to be 187.60, 190.60 and 108.10 and 1501.00 mg g-1 in 180 min, respectively. By comparison, we found that doping vanadium could play an important role in the adsorption processes. The adsorption capacity of C-V-1 (containing the vanadium in its structure) was relatively higher than that of C-N-1, which indicated that the introduction of non-noble metals may effectively tune the adsorption kinetics activity and the introduction of noble metals can change the surface electronegativity of porous carbon materials, thus leading to significantly improved adsorption capabilities.

Selective adsorption of organic dyes from aqueous environment using fermented maize extract-enhanced graphene oxide-durian shell derived activated carbon composite

A secure aquatic environment is essential for both aquatic and terrestrial life. However, rising populations and the industrial revolution have had a significant impact on the quality of the water environment. Despite the implementation of strong and adapted environmental policies for water treatment worldwide, the issue of organic dyes in wastewater remains challenging. Thus, this study aimed to develop an efficient, cost-effective, and sustainable material to treat methylene blue (MB) in an aqueous environment. In this research, maize extract solution (MES) was utilized as a green cross-linker to induce precipitation, conjugation, and enhance the adsorption performance of graphene oxide (GO) cross-linked with durian shell activated carbon (DSAC), resulting in the formation of a GO@DSAC composite. The composite was investigated for its adsorptive performance toward MB in aqueous media. The physicochemical characterization demonstrated that the cross-linking method significantly influenced the porous structure and surface chemistry of GO@DSAC. BET analysis revealed that the GO@DSAC exhibited dominant mesopores with a surface area of 803.67 m2/g. EDX and XPS measurements confirmed the successful cross-linking of GO with DSAC. The adsorption experiments were well described by the Harkin-Jura model and they followed pseudo-second order kinetics. The maximum adsorption capacity reached 666.67 mg/g at 318 K. Thermodynamic evaluation indicated a spontaneous, feasible, and endothermic in nature. Regenerability and reusability investigations demonstrated that the GO@DSAC composite could be reused for up to 10 desorption-adsorption cycles with a removal efficiency of 81.78%. The selective adsorptive performance of GO@DSAC was examined in a binary system containing Rhodamine B (RhB) and methylene orange (MO). The results showed a separation efficiency (α) of 98.89% for MB/MO and 93.66% for MB/RhB mixtures, underscoring outstanding separation capabilities of the GO@DSAC composite. Overall, the GO@DSAC composite displayed promising potential for the effective removal of cationic dyes from wastewater.

Carbon nanotube/Chitosan hydrogel for adsorption of acid red 73 in aqueous and soil environments

Acid red 73 is an azo dye, and its residue can pollute the environment and seriously threaten human health and life. In this study, glutaraldehyde was used as the crosslinking agent, chitosan and polyvinyl alcohol were crosslinked under appropriate conditions to obtain a chitosan hydrogel film, and carbon nanotubes were dispersed in the chitosan hydrogel film. The FTIR, XRD, BET, SEM were applied to chatacterize the structure and the morphology of the absorbent and results showed that when the mass fraction of the carbon nanotubes was 1%, the structure was a three-dimensional network with microporous, and the water absorption reached to the maximum value of 266.07% and the elongation at break reached to a maximum of 98.87%. The ability to remove acid red 73 from aqueous and soil environments was evaluated by UV. In the aqueous samples, 70 mg of the adsorbent reached a saturated adsorption capacity of 101.07 mg/g and a removal rate of 92.23% at pH = 5. The thermodynamics conformed with the Langmuir adsorption isotherm and pseudo second-order adsorption kinetic models. In the soil samples, 100 mg of the adsorbent reached an adsorption capacity of 24.73 mg/g and removal rate of 49.45%. When the pH of the soil is between 4 and 7, the removal rate and adsorption capacity do not change much; hence, the pH should be maintained between 5.2 and 6.8, which is extremely suitable for the growth of general plants. Moreover, the experimental results demonstrated that the adsorbent maintained a good removal rate of acid red 73 over six adsorption cycles.

Trimetallic carbon-based catalysts derived from metal-organic frameworks for electro-Fenton removal of aqueous pesticides

Pesticide overuse has posed a threat to agricultural community as well as aquatic animals. Heterogeneous electro-Fenton (HEF) processes have received considerable attention for aqueous contaminants removal, and metal-organic frameworks (MOFs) serve as promising templates for fabrication of carbon-based HEF catalysts with low Fe leaching and enhanced stability. Herein, multimetallic MOF-derived HEF catalysts CMOFs@PCM have been demonstrated as efficient and stable HEF catalysts for aqueous pesticide degradation and mineralization. The porous carbon monolith (PCM) substrate effectively catalyzed 2-electron oxygen reduction reaction (ORR) over the pH range of 4-10 to in situ generate H₂O₂, which was then activated by the anchored Fe₃O₄, Fe₃C and NiO into OH for pesticide degradation. Fe₈Al₇Ni₅-CMOF@PCM achieved over 90% napropamide degradation within 60 min in the pH range of 4-10, and 96% degradation at neutral condition, 39% higher than monometallic CMIL-88(Fe)@PCM. Meanwhile, the embedded NiO and γ-Al₂O₃ showed synergistic effect in promoting the catalytic activity of Fe sites, resulting in substantially enhanced performance of trimetallic Fe_xAl_yNi_z-CMOF@PCM compared to the monometallic counterparts. On the other hand, the unique core-shell structure and Fe₃C interlayer formed by co-pyrolyzing Fe-containing MOFs-NH₂ with PCM greatly minimized the metal leaching and enhanced the stability of the electrocatalysts.

Synthesis of chitosan composite of metal-organic framework for the adsorption of dyes; kinetic and thermodynamic approach

The iron metal-organic framework composite with chitosan (CS/MOF-235) was synthesized using a solvothermal method and its synthesis was confirmed by surface area, PZC, XRD, FESEM, XPS, TGA, TEM, EDX mapping and EDX analysis. The chitosan composite of the iron metal-organic framework (CS/MOF-235), MOF-235 and chitosan were used for the removal of methylene blue (MB) and methyl orange (MO) from aqueous solutions. The maximum adsorption capacities were found to be 2857-2326 mg/g for CS/MOF-235, 357 - 236 mg/g for MOF-235 and 209-171 mg/g for chitosan (CS) which reveal that the adsorption capacity of CS/MOF-235 is almost 8 and 14 times greater than MOF-235 and chitosan respectively. The adsorption selectivity of the (CS/MOF-235) towards the dye was in the order MO > MB. Moreover, hydrogen bonding, pi-pi bonding, pore-filling, electrostatic interactions and chemisorption were proposed as possible mechanisms for the removal of dyes onto CS/MOF-235. The intraparticle diffusion and Richenberg models confirmed that the adsorption process was jointly controlled by the pore and film diffusion. The negative values of the isosteric heat of adsorption (ΔH¯) fall with surface coverage indicating that a lesser amount of heat is required for the greater uptake of dyes.