Efficient Capture-and-Release Mechanism via a Spin Crossover-Mediated Change in Gas Affinity in Metal-Organic Frameworks from Ab initio Calculations

The development of strategies to efficiently capture and release gas is one of the most studied topics in modern applied chemistry. In this respect, the modulation of the affinity for the gas molecule upon application of an external stimulus appears as fascinating strategy to reduce the energy penalty of the release process. In this work we provide the proof-of-concept for a novel temperature-induced gas release strategy in porous materials with desorption occurring upon a spin crossover transition of metal center exhibiting an open coordination. By employing a recently proposed Hubbard-U density-corrected scheme within density-functional theory we demonstrate the feasibility of the proposed process from a thermody- namic point of view by correlating the change in binding energy of several gas molecules upon spin crossover with the adiabatic energy difference associated with the spin state change for a series of six porous coordination polymers. The case of H2 adsorption stands out as the most promising and yet novel result with implications for a non-cryogenic storage technology.