Exploiting a Lattice-Driven Gating in a Cu-Based Zeolitic Imidazolate Framework for Efficient High-Temperature Hydrogen Isotope Separation

Abstract

This study presents a novel approach for hydrogen isotope separation using Cu-ZIF-gis, a Cu-based zeolitic imidazolate framework with ca. 2.4 Å channels. Traditional Kinetic Quantum Sieving(KQS) method involves exploiting diffusion barriers, caused by the flexibility of local linker molecules or unit cell breathing phenomena. However, these methods are ineffective at high temperatures, as such opening transition typically completes below 77K. Cu-ZIF-gis leverages a new approach named "Lattice-driven gating", which uses lattice expansion to control the aperture at elevated temperatures up to 180K. Despite the lack of strong binding sites, it achieves effective isotope uptake via KQS above 120K and shows exceptional stability, remaining intact for nearly 3 years in air. With the help of Quasi-Elastic Neutron Scattering(QENS), we observe substantial differences in the molecular mobility of H₂ and D₂ above 150K. This method is compatible with existing LNG cryo-infrastructure, marking a significant advancement in sustainable isotope separation technologies.