Specific\nIsotope-Responsive Breathing Transition in\nFlexible Metal–Organic Frameworks

Abstract

An\nisotope-selective responsive system based on molecular recognition\nin porous materials has potential for the storage and purification\nof isotopic mixtures but is considered unachievable because of the\nalmost identical physicochemical properties of the isotopes. Herein,\na unique isotope-responsive breathing transition of the flexible metal–organic\nframework (MOF), MIL-53­(Al), which can selectively recognize and respond\nto only D₂ molecules through a secondary breathing transition,\nis reported. This novel phenomenon is examined using <i>in situ</i> neutron diffraction experiments under the same conditions for H₂ and D₂ sorption experiments. This work can guide\nthe development of a novel isotope-selective recognition system and\nprovide opportunities to fabricate flexible MOF systems for energy-efficient\npurification of the isotopic mixture.