The ability to tune the pore size, shape and functionality of crystalline porous coordination polymers or metal-organic frameworks (MOFs) has made this class of materials attractive for a wide range of adsorption-based applications. As a particular example, the flexibility and guest molecule-dependent response of MOFs leads to unexpected adsorption phenomena. In this context, we report a computational study that combined with a series of experimental tools evidences and provide insight into the origin of the unprecedented negative gas adsorption (NGA) behaviour of DUT-49 (DUT stands for Technische Universität Dresden). Monte Carlo simulations showed that the concentration dependence of the pore filing controls the sudden structural shrinkage of this MOF that switches from a LP to a NP form to expulse CH4 at a given pressure. These findings may enable technologies using frameworks capable of NGA for pressure amplification in micro- and macroscopic system engineering. We further focus on a spectacular capture of N2 for both natural gas upgrading and air separation using a mesoporous MOF. A combination of Density Functional Theory and Monte Carlo simulations revealed that the separation mechanism for both N2/CH4 and N2/O2 gas mixtures is driven by specific interactions with specific adsorption sites that allow a much stronger binding of N2 vs CH4 and O2. This concept opens new horizons to address several challenges in chemistry, such as the removal of nitrogen or the design of heterogeneous biomimetic catalysts through nitrogen fixation. Another topic of interest will be devoted to the discovery of a new MOF with unprecedented performances for the dehydration of natural gas.

Understanding of spectacular gas adsorption/separation phenomena in metal-organic frameworks

253rd National Meeting (2017)

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