The discovery of a new nanoporous compound that has unique porous properties is scientifically and technologically topical. The creation of a porous compound that can effectively separate small molecules that are in gas phase at standard temperature and pressure is currently one of major challenges in material science. In particular, the separation and purification of energy-related gases such as hydrocarbons, oxygen, carbon monooxide etc. are getting more important because of the strong social demands of the environmental sustainability. The recent advent of porous coordination polymers (PCPs) or metal�organic frameworks (MOFs) as new crystalline microporous compounds, has attracted the attention of scientists because of the great practicality of regular nano-sized spaces.Here we report soft MOFs that show structural transformation in response to the adsorption of specific guest molecules or external stimuli, resulting in high selectivity for guest inclusion1-3. Dynamic effects can arise either locally from flexible ligands and/or flexibility of the coordination geometry of the metal ions, or from the global cooperative movement of the framework on a periodic scale. We will also report new soft MOFs that selectively adsorb CO with adaptable pores. The high selectivity toward CO was achieved by the synergetic effect of the local interaction between CO and accessible metal sites and a global transformation of the framework, which was elucidated by various techniques including in-situ X-ray powder diffraction/sorption experiments. The transformable crystalline materials realized the separation of CO from a mixture with nitrogen (N2), a gas that is the most competitive to CO (Figure 1). The dynamic and efficient molecular trapping and releasing system so-called self-accelerating CO sorption is reminiscent of sophisticated biological systems such as heme proteins4.

Highly selective adsorption and separation of energy-related gases on soft metal-organic frameworks

248th National Meeting (2014)

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