Selective, adsorbate-induced spin state changes in transition metal-based metal-organic frameworks

A method of separating a selected component of gas molecules from a mixture of components of gas molecules using a metal organic framework, the method comprising:

• exposing a porous material to said mixture of components of gas molecules, the porous material having the metal organic framework comprising:
• a transition metal of iron (Fe);
• and
• a plurality of organic molecules coordinated to said transition metal to form a Fe-organic molecule framework so as to preserve open coordination sites for molecules to be selectively adsorbed to provide selectively adsorbed molecules,
• wherein said selectively adsorbed molecules have π* orbitals adapted to accept electron density from said transition metal,
• wherein said transition metal is in a high-spin electron configuration in the absence of the selectively adsorbed molecules, said high-spin electron configuration defining a high-spin configuration of the transition metal,
• wherein said transition metal converts to a low-spin electron configuration defining a low-spin configuration of the transition metal in the presence of said selectively adsorbed molecules that are bonding to said transition metal by donating electron density to the π* orbitals of the selectively adsorbed molecule, such that upon exposure to the selectively adsorbed molecules said transition metal undergoes a spin state transition, and
• wherein said transition metal remains high-spin electron configuration in the presence of non-selected molecules that are non-bonding to said transition metal;
• and
• separating said selected component of gas molecules including the selectively adsorbed molecules from said mixture of components of gas molecules after being exposed to said porous material,
• wherein said selected component of gas molecules being separated from said mixture of components of gas molecules are adsorbed preferentially by said porous material during said exposing compared to adsorption of other components of gas molecules including the non-selected molecules in said mixture of components of gas molecules.