2-Dimensional Intercalated Cyano-Metallate Complexes- Approach to Ultrafiltration
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The discovery of graphene and other two-dimensional (2-D) materials has opened the way for a huge opportunity in material development, manipulation, and their corresponding potential applications. 2-D materials including graphene have been shown to have unique properties such as high electrical conductivity, high mobility, and high surface area. These properties have made 2-dimensional materials amenable to small scale electronic applications, molecular sieves and for high strength composite applications. Despite the promise graphene holds, it has been difficult to completely harness its potential because it is difficult and expensive to produce single layer graphene sheets in substantial quantity. A unique class of 3-dimensional nanomaterials that can be produced in substantial quantity and cost effectively processed into 2-dimensional hybrid structures are the Metal Organic Frameworks (MOFs). MOFs, which are basically a composition of molecular complexes formed between metals and salts, organic and inorganic molecules, have been rationalized to be a coordination complex with a stereospecific structure. Transition Metal Cyanates are a unique class of 3-dimensional cyanometallate network. The most common are hexacyano transition metal complexes with divalent transition metal counter ions. We have prepared and exfoliated transition metal cyanates into 2-dimensional structures by exfoliation into separates sheets. Hybrid 2-D structures have also been produced and studied by intercalation with organic linkers.
Density Function Theory (DFT) studies have predicted an increase in the d spacing of potassium tetra-cyanonickelate, on substitution with di-metallic cation such as Fe2+, Mn2+, Cd2+ and Co2+, and additional processing with organic linkers. Dodecyl pyrrolidone (DDP) was used to intercalate the metal complexes and X-ray diffraction results showed significant peak shifts to the left on all metal complexes, corroborating the DFT predictions. The increased distance between layers allows for further separation into exfoliated sheets. In this report, we have demonstrated an approach for producing a long range defect-free 2-D sheets. We have grown di-metallic cation complexes of Fe2+, Mn2+, Ni2+ and Co2+ on Teflon supports. This was done by placing hydrophilic 1.0 micron Teflon as a barrier between a desired salt of the complex and potassium tetracyano nickelate. The desired metal complex was formed by diffusion of the opposing solution in the Teflon support. The membrane was dried and used as barrier for Na+ ion selectivity test. The test was carried with 1.0 M NaCl. The solution was pumped under vacuum through the membrane, and a pristine membrane was used as a control. Results showed that the Fe and Mn tetracyano nickelate selectively reject Na+ ion salts while control experiments proved otherwise.
These results hold promise for material applications in waste water remediation, separations, desalination, and purification. In this work, we also reported a simple process of synthesizing Nickel Ferrite-graphitic layers with inverted magnetic hysteresis.