Victor V. Terskikh

Efficient separation and storage of radioactive noble gas isotopes [krypton-85 ( ⁸⁵ Kr) and xenon-131m/133/135 ( ^131m/133/135 Xe)] from off-gas during spent nuclear fuel reprocessing are vital for environmental protection and noble gas recovery. Metal-organic frameworks (MOFs) are promising adsorbents, yet atomic-level insights into Xe and Kr adsorption remain limited. Here, we report the first application of high-field solid-state ⁸³ Kr nuclear magnetic resonance (NMR), alongside extensive ¹²⁹ Xe NMR, to investigate gas adsorption in eight MOFs representing three design strategies: ultramicroporous one-dimensional–channel MOFs with pore sizes matching noble gas diameters, functionalized MOFs, and MOFs with open metal sites. Single-gas and coadsorption studies reveal distinct adsorption sites, guest-host interactions, and gas dynamics in each MOF. Most MOFs retain crystallinity after exposure to 60-kilogray γ radiation. Several radiation-sensitive MOFs exhibit enhanced stability in the presence of Xe, suggesting that Xe adsorption enhances framework stability and may broaden the range of MOFs usable under γ radiation in nuclear off-gas separation. These findings offer valuable molecular-level design insights.

Germanium substitution in Cu ₂ ZnSnS ₄ has been previously shown to improve power conversion efficiencies, but detailed information about the local structure within solid solutions Cu ₂ ZnSn _{1− x} Ge _x S ₄ has so far been lacking.

We report solid-state ¹H and ¹⁷O NMR results for four ¹⁷O-labeled organic compounds each containing an extensive carboxyl-bridged hydrogen bond (CBHB) network in the crystal lattice: tetrabutylammonium hydrogen di-[¹⁷O₂]salicylate (1), [¹⁷O₄]quinolinic acid (2), [¹⁷O₄]dinicotinic acid (3), and [¹⁷O₂]Gly/[¹⁷O₂]Gly·HCl cocrystal (4). The ¹H isotropic chemical shifts found for protons involved in different CBHB networks are between 8.2 and 20.5 ppm, which reflect very different hydrogen-bonding environments. Similarly, the ¹⁷O isotropic chemical shifts found for the carboxylate oxygen atoms in CBHB networks, spanning a large range between 166 and 341 ppm, are also remarkably sensitive to the hydrogen-bonding environments. We introduced a simple graphical representation in which ¹H and ¹⁷O chemical shifts are displayed along the H and O atomic chains that form the CBHB network. In such a depiction, because wavy patterns are often observed, we refer to these wavy patterns as ¹H/¹⁷O chemical shift waves. Typical patterns of ¹H/¹⁷O chemical shift waves in CBHB networks are discussed. The reported ¹H and ¹⁷O NMR parameters for the CBHB network models examined in this study can serve as benchmarks to aid in spectral interpretation for CBHB networks in proteins.

A pair of novel polymorphic ionic cocrystals of 3,4‐dicyanotelluradiazole and tetraphenylphosphonium bromide are synthesized and are characterized by single‐crystal XRD. Strong and directional non‐covalent chalcogen bonds (ChB) between Te and Br are analyzed via solid‐state NMR to reveal large and anisotropic J(¹²⁵Te,^79/81Br) coupling tensors, providing unequivocal evidence for non‐Fermi contact contributions across ChBs. Along with large ^79/81Br quadrupolar couplings for the Br⁻ anions, these data provide new tools to characterize chalcogen bonds and to differentiate between ChB polymorphs.

A pair of novel polymorphic ionic cocrystals of 3,4‐dicyanotelluradiazole and tetraphenylphosphonium bromide are synthesized and are characterized by single‐crystal XRD. Strong and directional non‐covalent chalcogen bonds (ChB) between Te and Br are analyzed via solid‐state NMR to reveal large and anisotropic J(¹²⁵Te,^79/81Br) coupling tensors, providing unequivocal evidence for non‐Fermi contact contributions across ChBs. Along with large ^79/81Br quadrupolar couplings for the Br⁻ anions, these data provide new tools to characterize chalcogen bonds and to differentiate between ChB polymorphs.

^63/65 Cu solid-state NMR spectroscopy provides a wealth of information regarding the local geometry and bonding at Cu( i ) in metal–organic frameworks. This approach is also applicable when systems contain Cu( ii ) centers or at lower magnetic fields.

One-and two-dimensional H-1, H-2, C-13,and Zn-67 NMR experiments, paired with computationalmethods, reveal CO2 and H2O adsorption locations,dynamics, and host-guest interactions in the ultramicroporousZnAtzOx MOF across a range of guest loading levels. Computationalresults permit visualizations of the adsorption locations and spatialdistribution of guests in various scenarios. This experimental methodologycan be used to investigate humid carbon capture and storage applicationsin other MOFs. Climate change from anthropogenic carbon dioxide (CO2) emissions poses a severe threat to society. A variety ofmitigationstrategies currently include some form of CO2 capture.Metal-organic frameworks (MOFs) have shown great promise forcarbon capture and storage, but several issues must be solved beforefeasible widespread adoption is possible. MOFs often exhibit reducedchemical stabilities and CO2 adsorption capacities in thepresence of water, which is ubiquitous in nature and many practicalsettings. A comprehensive understanding of water influence on CO2 adsorption in MOFs is necessary. We have used multinuclearnuclear magnetic resonance (NMR) experiments at temperatures rangingfrom 173 to 373 K, along with complementary computational techniques,to investigate the co-adsorption of CO2 and water acrossvarious loading levels in the ultra-microporous ZnAtzOx MOF. Thisapproach yields detailed information regarding the number of CO2 and water adsorption sites along with their locations, guestdynamics, and host-guest interactions. Guest adsorption andmotional models proposed from NMR data are supported by computationalresults, including visualizations of adsorption locations and thespatial distribution of guests in different loading scenarios. Thewide variety and depth of information presented demonstrates how thisexperimental methodology can be used to investigate humid carbon captureand storage applications in other MOFs.

Metal halide perovskites remain top candidates for higher-performance photovoltaic devices, but concerns about leading lead-based materials remain. Ge perovskites remain understudied for use in solar cells compared to their Sn-based counterparts. In this work, we undertake a combined ⁷³Ge and ¹³³Cs solid-state Nuclear Magnetic Resonance (NMR) spectroscopy and density functional theory (DFT) study of the bulk CsGeX₃ (X = Cl, Br, or I) series. We show how seemingly small structural variations within germanium halide perovskites have major effects on their ⁷³Ge and ¹³³Cs NMR signatures and reveal a near-cubic phase at room temperature for CsGeCl₃ with severe local Ge polyhedral distortion. Quantum chemical computations are effective at predicting the structural impact on NMR parameters for ⁷³Ge and ¹³³Cs. This study demonstrates the value of a combined solid-state NMR and DFT approach for investigating promising materials for energy applications, providing information that is out of reach with conventional characterization methods, and adds the challenging ⁷³Ge nucleus to the NMR toolkit.