日本ゼオライト学会　刊行物 Publication of Japan Zeolite Association

To achieve carbon neutrality, progress is being made in reducing CO₂ emissions and using renewable energy, but these efforts alone have limitations. Therefore, the development of CO₂ capture technology is essential. In this regard, intensive research and development is being carried out in the fields of absorption, membranes and adsorption, with particular attention being paid to flexible metal–organic frameworks (MOFs) that have structural flexibility. Flexible MOFs exhibit a stepwise adsorption behavior (gate opening) with structural deformation at a certain threshold pressure. The stepwise change in adsorbed amount facilitates easy recovery of adsorbents, and the gas-specific transition pressure induces high gas selectivity. In addition, the “intrinsic thermal management capability,” which offsets the heat of adsorption with the heat of structural transition, makes it possible to minimize the degradation of adsorption performance due to temperature rise in pressure swing adsorption (PSA) processes operated under temperature uncontrolled conditions. These unique properties, not found in conventional materials, synergistically contribute to an innovative process that outperforms previous adsorption separations. In this commentary, we introduce the potential of CO₂ adsorption separation processes using flexible MOFs based on our research results of ELM-11.