Nuclear-spin isomers—such as ortho- and para-H2—are specific quantum states of molecules that differ only in the spin alignment of their nuclei. Though structurally indistinguishable, these isomers can exhibit drastically different reactivity, thermodynamic properties, and lifetimes. The ability to control and prepare nuclear-spin states in the laboratory opens new frontiers in quantum-controlled chemistry, energy storage, catalysis, and astrochemistry.
Our group is developing an experimental platform to prepare, trap, and optically characterize molecules in specific nuclear-spin isomeric states. This work aims to enable state-resolved reactivity measurements and explore how spin symmetry affects molecular energy storage.
Figure 1. Our closed-cycle cryostat system enables high-resolution spectroscopy of materials cooled below 20 K.
At the heart of our approach is a closed-cycle helium cryostat system integrated with a commercial Fourier-transform infrared (FTIR) spectrometer. Samples—typically porous powders—are embedded in optically transparent matrices or pressed into thin wafers. This allows us to perform infrared spectroscopy on a wide range of materials, including metal-organic frameworks (MOFs), covalent-organic frameworks (COFs), and zeolites, at temperatures where nuclear-spin populations can be enriched.
We use this platform to study gas/surface interactions between molecules (e.g., H2, CH4, H2O) and the cryogenically cooled internal surfaces of porous materials. In particular, we are investigating how paramagnetic centers within these materials can catalyze nuclear-spin conversion—an effect that could be exploited for energy storage, magnetic separation, or quantum-state purification.
An early demonstration showed that cryogenic spectroscopy is feasible for porous crystalline solids (provided by the Taylor group at UMD), validating the technique across a new class of materials. Building on this, we are now targeting quantum-state-resolved spectroscopy of H2 in confinement, with an eye toward catalytic control of ortho–para conversion.
Selected Publication
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Frimpong, J. K., McLane, N. et al. “Temperature-dependent structural dynamics in covalent organic frameworks observed by cryogenic infrared spectroscopy,”
Phys. Chem. Chem. Phys., 2024, 26, 22252–22260.
DOI: 10.1039/D4CP02338B