Construction of a polyoxometalate-based magnetic composite MOF for the effective adsorption of cationic dyes

Adsorption and separation of dyes are extremely important as they damage the water environment and human health. ZIF-8 has the benefits of large specific surface area, explicit structure and a good confinement effect on POM, which can better facilitate the synergetic effect of POM and ZIF-8. Therefore, ZIF-8 was chosen as the support material to wrap H₃PW₁₂O₄₀. In the present work, magnetic ZIF-8@H₃PW₁₂O₄₀ composites were prepared by a facile impregnation synthesis strategy and applied to the adsorption of cationic dyes with methylene blue (MB) as a representative. Compared with the other three prepared materials, Fe₃O₄@ZIF-8@H₃PW₁₂O₄₀ exhibited the best adsorption performance. The adsorption process conformed to the pseudo-second-order model and the Langmuir model, and the adsorption reaction was spontaneous with the maximum adsorption capacity of up to 431.03 mg g^-1 within 20 min. The electrostatic attraction has been testified to be the major driving force of the adsorption process, and the material can still hold 90% of the max adsorption capacity after 5 cycles, which serve as the foundation for its further applications in the field of adsorption.

Metal Cation Triggered Peptide Hydrogels and Their Application in Food Freshness Monitoring and Dye Adsorption

Metal-ligand interactions have emerged as an important tool to trigger and modulate self-assembly, and to tune the properties of the final supramolecular materials. Herein, we report the metal-cation induced self-assembly of a pyrene-peptide conjugate to form hydrogels. The peptide has been rationally designed to favor the formation of β-sheet 1D assemblies and metal coordination through the Glu side chains. We studied in detail the self-assembly process in the presence of H+, Li+, Na+, K+, Ca2+, Ni2+, Cu2+, Zn2+, Cd2+, Co2+, Fe3+, and Cr3+ and found that the morphology and mechanical properties of the hydrogels are ion-dependent. Moreover, thanks to the presence of the metal, new applications could be explored. Cu2+ metallogels could be used for amine sensing and meat freshness monitoring, while Zn2+ metallogels showed good selectivity for cationic dye adsorption and separation.

Co-assembly of charge complementary peptides and their applications as organic dye/heavy metal ion (Pb2+, Hg2+) absorbents and arsenic(iii/v) detectors

Learning from nature, molecular self-assembly has been used extensively to generate interesting materials using a bottom up approach. The enthusiasm in this field of research stems from the unique properties of these materials and their diverse applications. The field has not been limited to studying assembly of similar types of molecules but extended to multi component systems via the co-assembly phenomenon. We have designed two charge complementary peptides to study their co-assembly in mechanistic detail in the present work. The cooperative self-assembly is mainly driven by electrostatic interaction that is aided by aromatic interactions, hydrogen bonding interactions and hydrophobic interactions. The hydrogels obtained have been employed in waste water remediation. Both the self-assembled and co-assembled hydrogels are capable of removal of different kinds of organic dyes (cationic, anionic and neutral) and toxic metal ions (Ni²⁺, Co²⁺, Pb²⁺ and Hg²⁺) individually and as a mixture from water with high efficiency. Additionally, the peptides developed in this study can act as ion sensors and detect arsenic in its most toxic (III/V) oxidation states. Molecular understanding of the assembly process is of fundamental importance in the rational design of such simple, robust yet economically viable materials with versatile and novel applications.

Self- and co-assembled gels from charge complementary peptides with waste water remediation applications.