The fundamental strategy to realize specific or highly selective adsorption process is based on the understanding of the chemical and physical properties of the adsorbed molecules and the design and synthesis of nanoporous compounds that can recognize the differences between the various gases [1]. This requires precise control of the structure and detailed understanding of the structure-property relationships. Therefore, study on host-guest interactions in nanoporous framework is important for understanding adsorption processes for highly selective gas adsorption and/or separation ability. Recently, computer simulation has become an indispensable research tool because often experiments require theoretical interpretation and computing power has grown rapidly in the last decade. Due to the regularity of the metal-organic framework (MOF) material, in a computer simulation we are easily able to build structural models of MOFs that are very helpful to find new materials with desired characteristics [2]. The aim of this study is detailed theoretical analysis the adsorption of targeted molecules into selected nanoporous materials in order to accelerate the realization of novel materials, hand-in-hand with experiment. In collaboration with experimentalists, we have shown that the concept of using designable regular MOF material could be applicable to a highly stable, selective adsorption systems [3,4]. Recently, the CO2 adsorption mechanism into Mn3(Hpdc)2(pdc)2 and Mg3(Hpdc)2(pdc)2 has been studied. The first compound experimentally shows extremely high extent of adsorption hysteresis while second one demonstrates no visible hysteresis loop. For both compounds, the extensive DFT simulations of the energetics and the location of the adsorbed CO2 molecules under gradual molecule-by-molecule feeling of the framework with guest CO2 molecules have been tracked in order to reveal the difference in sorption pathways. It has been found that guest-guest interaction plays an important role in formation a stable CO2 chain configuration inside the framework channel. A very pronounced step observed in experimental adsorption isotherm has been explained by delaying of the chain formation that associated with low guest permeability inside the Mn-MOF pore.

Role of guest-host and guest-guest interactions in selective gas adsorption in MOF materials: Theoretical aspects

256th National Meeting (2018)

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