Highly effective quantum sieving of hydrogen isotopes on flexible metal-organic frameworks with mobile ligands

Abstract

The separation of hydrogen isotopes is crucial in nuclear energy and biomedicine, but current techniques have limited separation coefficients. Utilizing flexible metal-organic frameworks (MOFs) with quantum sieving capabilities offers a promising solution. However, achieving high hydrogen isotope adsorption capacity while maintaining a high separation factor remains a challenge. This study presents a novel approach for the quantum sieving of hydrogen isotopes using MOFs with mobile ligands. The stable crystal structure of the microporous MOFs enables large hydrogen isotope adsorption capacity. The presence of mobile ligands acts as the gate in the dynamic adsorption and separation process, enhancing the performance of hydrogen isotope separation. The smaller quantum radius and larger molecular weight of deuterium facilitate its easier entry into the micropores, resulting in a maximum selectivity for D2 over H2 of 36.7 and a D2 uptake of 17.3 mmol g−1. Furthermore, the kinetic quantum sieving of hydrogen isotopes necessitates MOFs with mobile ligands that maintain their flexibility from 20 K to 70 K, as demonstrated by ultralow-frequency Raman spectra.