Structural and electronic properties of the Metal-Organic Frameworks M-URJC-1 (M = Cu, Fe, Co or Zn): An in-silico approach aiming the application in the separation of alcohols

Alcohols in high degree of purity are required in many applications, as for example as fuels. The main method used to separate and concentrate these compounds is distillation, which demands a high energetic cost. Therefore, alternative methods, as adsorptive separations are being pointed out as a very promissor and more cost-effective methodology. Metal-Organic Frameworks (MOFs) are solids that can be used as adsorbents for this purpose. These materials present a very diversified and adjustable structure, in such a way that unveiling the influence of their composition at the molecular level can help the design of materials with optimized properties for the desired application. In this work, the MOFs M-URJC-1 (M = Cu, Fe, Co or Zn) were evaluated as ad-sorbents aiming the separation of different alcohols (methanol, ethanol, propa-1-ol and butan-1-ol) and also from water, carbon dioxide and methoxymethane. Computational simulations were performed based on Density Functional Theory under periodic boundary conditions. It was identified that the MOFs M-URJC-1 can differentiate the guest molecules allowing their separation mainly through three kinds of interactions. Firstly, the coordination in the metallic cations of the materials, in which the interaction is strongly for the harder metallic cations. Secondly, the formation of hydrogen bonds with the available nitrogen atoms from the structure of MOFs, in which the conventional are stronger than the non-conventional ones. Finally, the hydrophobic in-teractions involving the carbonic chains of the molecules, which are stronger for the alcohols with longer chains.