Ligands have been extensively used to modulate and improve the photophysical properties of nanocrystals (NCs). However, the surface structure of many NCs remains unknown. In this study, we synthesized oleate-capped CdSe NCs, exchanged them with oleylamine/CdCl2, and used dynamic nuclear polarization (DNP)-enhanced solid-state NMR spectroscopy to determine the structure of surface Cd atoms bound to ligands. 113Cd and 77Se NMR experiments distinguish different types of 113Cd and 77Se environments in the CdSe NCs. DNP-enhanced 113Cd magic angle turning (MAT) experiments enable the identification of one bulk and two surface Cd environments in CdSe NCs, while DNP-enhanced 15N{1H} and 15N{113Cd} heteronuclear correlation experiments reveal nitrogen coordinated Cd atoms on the surface of the CdSe NCs. Indirect detection of chloride ligands was achieved using DNP-enhanced 113Cd{35Cl} J-resolved experiments, revealing that the chlorides bridge between surface Cd atoms. Comparing the experimental NMR spectra to relativistic density functional theory calculation models establishes two distinct surface Cd environments that differ by their ligand environments: one site is coordinated by one amine and a bridging chloride, while the other is coordinated by two amines.

Rare earth elements (REEs) are essential to modern technologies yet are typically sourced from regolith clays containing cation-exchanging minerals such as kaolinite, and conventional extraction methods often rely on environmentally harmful organic solvents. Deep eutectic solvents (DESs) provide a more sustainable alternative due to their tunable solvation properties, low volatility, and high thermal stability. Kaolinite contributes nanoscale features that enhance its suitability for REE separations, including its layered morphology featuring nanometer-scale layer thickness, heterogeneous surface charge, and structurally defined aluminol and silanol edge sites, all of which create reactive interfaces capable of strong electrostatic and inner-sphere interactions with multivalent cations. In this study, DESs were investigated for recovering ytterbium and neodymium (Yb3+ and Nd3+) from kaolinite, with the extraction time, temperature, and solvent composition systematically optimized. At an initial total REE concentration of 2.5 mg, kaolinite removed 99.4% of the REEs from solution, corresponding to a final loading of 0.49 mg g-1. Selective extraction with a choline chloride/lactic acid DES (1:8 molar ratio) yielded a conditional Nd3+/Yb3+ separation factor of 8.85, with Yb3+ showing stronger retention due to its smaller ionic radius and enhanced interaction with the kaolinite nanoscale framework. These findings underscore the potential of integrating kaolinite's nanoscale structural attributes with DES chemistry to enable efficient, selective, and environmentally benign REE recovery from regolith-derived resources.

Mesoporous silicon nitride (Si3N4) enables access to chemisorbed group IV organometallics catalysts active for propane dehydrogenation (PDH) compared to the organometallic analogues on mesoporous silica under the same reaction conditions. The series of Si3N4-supported materials are active catalysts, (Zr > Hf > Ti k f = 290, 232, and 162 mol mol(Metal)(-1) h(-1) at 450 degrees C with 2% C3H8 in Ar, respectively) with selectivity above 95%, demonstrating additional examples of Ti and Hf systems for PDH. However, the underlying mechanism of the improved performance relative to oxide supported homologues is not well-understood. Characterization of thermally treated samples (DRIFTS, XAS and SSNMR) and computational modeling of this catalyst series was utilized to differentiate between potential amido- (C-H activation along the M-N bond) and imido- (C-H activation along the M=N bond) mechanisms. Due to remaining mechanistic ambiguity, a Ga analogue was synthesized and evaluated for PDH activity as an indirect probe to experimentally differentiate pathways. An inversion of the oxide/nitride performance trend is observed for the Ga congener which does not form a Ga=N bond, most consistent with different mechanisms dictating the performance of the group IV/Si3N4 catalysts vs Ga/Si3N4.

C-H bond functionalization of arenes with boranes continues to be a challenge in catalysis, with late transition and rare earth metals shown to be catalytically active. In this study, group 4 metallocenes grafted onto acidic sulfated zirconia (SZO) are demonstrated to catalyze arene borylation with pinacolborane (HBpin). Catalysis studies at partial HBpin conversions (59-68%) using Cp2M(Me)/SZO (M = Ti, Zr, or Hf; Cp = cyclopentadienyl) catalysts reveal that Zr exhibits greater selectivity and activity than Ti and Hf. At 0.16 mol % of Zr, Cp2ZrMe/SZO achieves 332 turnovers at high HBpin conversion (86%), making this catalyst comparably active to previously reported Ir and Rh C-H borylation catalysts. At 160 °C, a maximum chemoselectivity of 82% for PhBpin was observed at 24% HBpin conversion. The superior activity of ionic Cp2ZrMe/SZO compared to neutral Cp2ZrMe/SiO2 demonstrates the borylation mechanism relies on the highly electrophilic, coordinatively unsaturated cationic sites stabilized by the weakly coordinating sulfated support. Furthermore, both catalysts significantly outperform their molecular analogues, Cp2ZrMe2 and [Cp2ZrMe][B(C6F5)4], suggesting that the support enhances catalytic performance by stabilizing the active species.

New methods for recovering the energy and value from polyolefin plastic waste must account for all the hydrocarbons formed during a deconstruction reaction. Analysis of the reaction mixture distribution is key to determining a catalyst's performance (activity and selectivity) and evaluating the economic viability of a conversion process. The molecular species present in the reaction mixtures can range from H2 and CH4 to hyper-branched hydrocarbons above 100,000 g/mol and any hydrocarbon in between; therefore, multiple analytical techniques are required to quantify all of the products. Here we describe an optimized and validated workflow that uses integrated analytical gas chromatography for concurrent H2 and gas-phase hydrocarbon quantification of the headspace; complementary gas chromatography, liquid chromatography and multi-nuclear magnetic resonance spectroscopy to quantify the composition of soluble products, as well as gel permeation chromatography to determine of the molecular weight distribution of the residual insoluble polymeric material. Using polyolefin hydrogenolysis in an autoclave reactor as an example, we describe how to specifically adapt these techniques to polymer deconstruction experiments and fully quantify the entire hydrocarbon population, while resolving and assigning specific species and characterizing structures. The information from this comprehensive analysis is needed to study reaction kinetics and to evaluate the intrinsic activity of a catalyst and reactivity of polymers in upcycling experiments, enabling mechanistic investigations and providing data to link experiment and theoretical models. The comprehensive quantitative analysis in this protocol can be completed within 4 d.

Achieving stable, selective single-atom catalysts is challenging because localsurface-site structures are difficult to control. Surface organometallic chemistry and organic-inorganic hybrid materials offer partial solutions, but applications to supporting zero-valent metals are limited. We demonstrate that well-defined, ionically bound N-heterocyclic phosphenium ([NHP]+) ligands can be generated on silylium-functionalized sulfated zirconia ([iPr3Si][SZO]). These surface-bound [NHP][SZO] ligands coordinate Pt(0) centers, forming [(NHP)Pt(0)L][SZO] precatalysts that are highly active for alkyne hydrosilylation. Systematic studies reveal that sterically bulky aromatic ligands enhance regioselectivity, achieving performances comparable to molecular Pt catalysts. Further, more-coordinating anions support more-regioselective precatalysts; therefore, SZO supports more-selective species than weaker-coordinating Al(OC(CF3)3)3-functionalized silica, a trend confirmed by molecular analogues. These results demonstrate that both the ligand and support control catalytic behavior and enable solid-state structure-activity relationships.

Variable-temperature 2H NMR reveals that the THF ligands are highly labile in Ln(BH4)2(THF)2/HY30, undergoing exchange between Ln sites under confinement via low-coordinate intermediates. Potency in catalytic C-H borylation likely emerges from access to highly electrophilic, electronically unsaturated species.

Semiconductor nanocrystals (NCs) are of interest due to their tunable electronic and optical properties. However, the characterization of surface structures of NCs remains an unresolved challenge. Here, we demonstrate that rotational-echo double-resonance (REDOR) experiments can be used to determine precise structural models of CdSe NC surfaces. An atom efficient ligandexchange scheme is demonstrated to introduce partially 13C-enriched oleate ligands onto CdSe NCs and enable 13C dephased REDOR experiments. DNP-enhanced 13C{77Se}, 77Se{13C}, 13C{111Cd} and 111Cd{13C} REDOR NMR experiments were performed on the 13C-enriched oleate-capped CdSe zinc blende CdSe NCs. Despite the modest isotope abundance of 77Se and

The iridium-pincer complex {p-OP( t Bu)2-C6H2-2,6-OP( t Bu)2]2}Ir(C2H4) (P[Ir]) has been reported as a stable and active catalyst toward alkane dehydrogenation in homogeneous and supported heterogeneous systems. Dehydrogenation has been shown as a practical method toward functional polyolefins, with dehydrogenated high-density polyethylene (deHDPE) demonstrated as a valuable synthon for upcycling, as orthogonal C-H strategies are key to end-of-life upcycling. The heterogenization of P[Ir] on oxides (SiO2, Al2O3, and TiO2; P[Ir]/E y O x ) yields a mixture of organometallic Ir-fragments whose catalytic nonoxidative dehydrogenation activity is modulated by the binding modes of the active metal on the surface. The binding mode was elucidated by a combination of solid-state NMR and XAFS analyses and supported by DFT calculations. Surface binding through the ligand enables active organoiridium that catalyzes internal olefination of deHDPE up to 1.23 mol % at 200 degrees C under dynamic vacuum. Alternatively, when the organoiridium is bonded though the metal center (Ir-OSiO), catalyst activity is negligible. Furthermore, the catalytic activity of P[Ir]/SiO2 showed comparable reactivity with the homogeneous analogue under the same catalytic conditions, and the heterogenized catalyst can be reused up to three cycles. This work highlights the importance of understanding how organometallic precursors react with hydroxylated metal oxide surfaces to establish structure-property relationships.

Nanocrystal surfaces generally undergo reconstructions that differentiate them from the bulk structures, often in nontrivial ways. Understanding these terminations is critical across diverse fields, from heterogeneous catalysis to the formation of topological states and the synthesis of semiconductor nanomaterials. Determining surface structures is currently an interdisciplinary task, most often involving high-resolution electron microscopy and surface electron diffraction. These methods, however, do not provide a global view of the ensemble of structures present in a sample. Here, we show how surface-sensitive solid-state nuclear magnetic resonance (SSNMR) spectroscopy methods can bridge this gap. In this context, we investigated the surface structure of lanthanum aluminate (LaAlO3) perovskite nanoparticles. Four distinct surface terminations have previously been observed for this material, but their relative abundances were unknown. Using an array of double- and triple-resonance SSNMR methods probing the relative proximities of surface 1H, 27Al, 17O, and 139La nuclei, we conclude the surface to be majority terminated (80%) by AlOx with substantial (20%) LaOx terminated regions.

Surface grafted organozirconium catalyzes C─H/Et─Al exchange reactions, involving saturated hydrocarbons and AlEt 3 , to afford organoaluminum compounds and ethane. The Zr(O t Bu) 3 @SiO 2 -Al 2 O 3–700 ( 1 ) catalyst contains monopodal ≡SiO─Zr(O t Bu) 3 and only a few residual silanols (<5%). Nonetheless, these silanols are the Achille's heel of 1 , providing a pathway for surface and catalyst degradation during catalysis, limiting the alkylaluminum yield and catalyst turnover. Support degradation, involving the cleavage of Si─O bonds by activated surface organometallics, is inhibited by capping silanols with ─SiMe 3 . Residual silanols in 1 react with allyltrimethylsilane, as determined by solid-state 13 C and 29 Si nuclear magnetic resonance (NMR) spectroscopy, infrared (IR) spectroscopy, and reaction stoichiometry, to form Zr(O t Bu) 3 /SiMe 3 @SiO 2 -Al 2 O 3–700 ( 2 ), which is resistant to degradation by AlEt 3 . C─H alumination of dodecane catalyzed by 2 produces higher yields of the 1-dodecylaluminum product in comparison to 1 , and in >95% selectivity. Additionally, methane undergoes 2 -catalyzed C─H alumination, providing a route to AlMe 3 .

Solid-state nuclear magnetic resonance (SSNMR) spectroscopy is a powerful technique for materials characterization, yet its application to air- and moisture-sensitive materials is often hindered by the difficulty in maintaining an inert environment during magic-angle spinning (MAS). This is particularly true for fast-MAS rotors that do not generally provide tight seals. Herein, we present a generalizable approach employing perdeuterated paraffin waxes-n-icosane-d42 and c-dodecane-d24-as protective embedding media to analyze sensitive organometallic catalysts using SSNMR. We demonstrate that these waxes significantly slow oxidative degradation under MAS conditions. Weak background 1H and 13C NMR signals from the waxes are effectively suppressed using double-quantum filtration and cross-polarization techniques. These findings offer a robust method for expanding the scope of SSNMR to air-sensitive systems, with implications for the structural study of reactive materials and catalysts.

It was recently reported that boron monoxide (BO) is formed through the cross-linking of B4O2 structural building units. Multiple theoretical phases agree with this description. Using pycnometry, multidimensional 17O NMR spectroscopy, and plane-wave DFT calculations we determined the likely polymorph to be a one-dimensional polymer initially proposed in 1955.

This review provides an up-to-date account of the development of two solid-state (SS)NMR methods for enhancing resolution and sensitivity, fast magic angle spinning (MAS) and dynamic nuclear polarization (DNP), and the resulting progress in surface science. We demonstrate the high resolution and efficiency that can be achieved by using two-dimensional homo- and heteronuclear correlation experiments with small rotors capable of MAS at rates exceeding 100 kHz. DNP has offered significant enhancements in signal sensitivity and allowed access to nuclei and experiments that are beyond the limits of conventional SSNMR. The continuing progress in fast MAS and DNP methodologies in recent years generated an unprecedented shift in SSNMR’s capabilities in the studies of surface and interface regions of solids, especially mesoporous supports and catalysts. We give numerous examples of recent applications and discuss the prospects for further improvements of both methods.

Lithium thioborates, despite their potential cost-effectiveness and low density, have received considerably less attention as solid electrolytes compared to their thiophosphate counterparts. A primary obstacle to their widespread investigation has been the inherent challenge in synthesizing single-phase materials. Computational studies have predicted several lithium thioborate phases exhibiting high ionic conductivity, with Li9B19S33 notably predicted to reach 80 mS cm-1. However, experimental validation of these theoretical predictions remains absent. This work addresses this gap by detailing a successful synthesis of the previously elusive Li9B19S33 phase, facilitated by in situ temperature dependent powder X-ray diffraction. Our findings reveal the peritectic nature of phase formation, necessitating an excess of boron sulfide in the reaction mixture. We further present a comprehensive structural characterization of Li9B19S33 utilizing spectroscopic techniques like NMR, FT-IR, and diffuse reflectance and report on its ionic conductivity. Solid-state 6Li NMR line narrowing experiments revealed an ion mobility activation energy of 0.26 eV whereas activation energies derived from impedance spectroscopy measurements were significantly higher, resulting in lower than theoretically predicted ionic conductivity.

The rotation frequencies of amido ligands are highly sensitive to the electronic structure of d0 transition metal complexes and have been used to study ligand donor properties. While attempting to study the donor properties of silanolate ligands in a silica-supported Cr complex, we observed highly restricted motions due to the added steric hindrance from the support, with only approximately half of the amides rotating on a 50 ms time scale. Surprisingly, when the same species is grafted into narrow 2.2 nm pores, all amido ligands are able to rotate. Density functional theory calculations suggest that confinement may limit the possible coordination sites and the configuration of the formed surface species, potentially enabling the formation of conformationally homogeneous surface site populations.

The anisotropic frequency shifts imparted onto the NMR resonance frequency depend on the spherical angular coordinates that describe the orientations of the NMR interaction tensors with respect to the applied magnetic field direction. Experiments performed using magic-angle spinning, however, gain a dependence on a third angle: the rotor phase γ. Traditionally, a carousel average is performed to integrate over γ, which leads to a slow convergence of intensities without contributing to the underlying powder patterns. Herein, we show an order of magnitude acceleration in computation time may be obtained by including the γ-averaging into the main powder average to eliminate redundant calculation of resonance frequencies.

Single atom, low valent transition metals are important for heterogeneous catalysis but are challenging to generate and stabilize in a well-defined manner. Herein, we explored the functionalization of silica with well-defined N-heterocyclic phosphenium (NHP) ions to heterogenize low-valent metals. The surface electrostatically bound [NHP]+ ions coordinate to Pt(0) precursors, resulting in well-defined, chemisorbed [(NHP)Pt(0)Ln]+ sites. The resulting materials catalyze the hydrosilylation of alkynes and exhibit activities and selectivities that rival the current industry standard homogeneous catalysts. The catalysts leach Pt, limiting their recyclability; however, recycling studies support that the high regioselectivities arise from heterogeneous sites and Pt particles do not form on the surface. We suspect that this phosphenium-based immobilization strategy will result in stable, tunable, low valent heterogeneous transition metal catalysts in a wider array of catalytic reactions.