Synergistic effect of paired Cu(II) open metal sites for enhanced high-temperature hydrogen isotope separation.
basic_science · Level V
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- Record sourced from PubMed, PMID 42706273.
- Also identified by DOI 10.1038/s41467-026-76556-7.
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Abstract
The selective separation of hydrogen isotopes under mild cryogenic conditions remains a formidable challenge due to their nearly identical physicochemical properties. Here, we report a dual strategy of pore topology design and paired Cu(II) open metal sites (OMS) synergistic engineering to amplify chemical affinity quantum sieving (CAQS). Among three tailored Cu(II)-MOFs, Cu-ATC exhibited exceptional performance, achieving a D<sub>2</sub>/H<sub>2</sub> selectivity of 20 at 50 K (10 mbar) and 1.8 in breakthrough experiments at 77 K, demonstrating excellent H<sub>2</sub>/D<sub>2</sub> separation performance. The ultramicroporous topology of Cu-ATC fixes a Cu···Cu distance of 5.98 Å within one-dimensional channels, while Jahn-Teller distortion induces axial elongation at each Cu(II) center, thereby enhancing the accessibility of the d<sub>z</sub><sup>2</sup> orbitals for interaction with hydrogen isotope molecules. This structural combination creates two closely spaced OMSs that enhance differential interactions with H<sub>2</sub> and D<sub>2</sub>, thereby driving isotope separation via CAQS. The distinct binding strength is evidenced by in situ DRIFTS (v(H-H)/ v(D-D) red-shift of 203 cm<sup>-1</sup>/ 147 cm<sup>-1</sup>) and by DFT calculations showing stronger adsorption of H<sub>2</sub> ( - 9.7 kJ mol<sup>-1</sup>) and D<sub>2</sub> ( - 13.0 kJ mol<sup>-1</sup>). These microscopic differences account for the observed D<sub>2</sub>/H<sub>2</sub> selectivity, highlighting the potential of paired OMSs engineering for CAQS-based isotope separation under mild cryogenic conditions.