Nuclear corepressors NCOR1/NCOR2 regulate B cell development, maintain genomic integrity and prevent transformation.

The nuclear corepressors NCOR1 and NCOR2 interact with transcription factors involved in B cell development and potentially link these factors to alterations in chromatin structure and gene expression. Herein, we demonstrate that Ncor1/2 deletion limits B cell differentiation via impaired recombination, attenuates pre-BCR signaling and enhances STAT5-dependent transcription. Furthermore, NCOR1/2-deficient B cells exhibited derepression of EZH2-repressed gene modules, including the p53 pathway. These alterations resulted in aberrant Rag1 and Rag2 expression and accessibility. Whole-genome sequencing of Ncor1/2 DKO B cells identified increased number of structural variants with cryptic recombination signal sequences. Finally, deletion of Ncor1 alleles in mice facilitated leukemic transformation, whereas human leukemias with less NCOR1 correlated with worse survival. NCOR1/2 mutations in human leukemia correlated with increased RAG expression and number of structural variants. These studies illuminate how the corepressors NCOR1/2 regulate B cell differentiation and provide insights into how NCOR1/2 mutations may promote B cell transformation.

The Role of Lewis Acid Sites in γ-Al2 O3 Oligomerization.

Olefin oligomerization by γ-Al2 O3 has recently been reported, and it was suggested that Lewis acid sites are catalytic. The goal of this study is to determine the number of active sites per gram of alumina to confirm that Lewis acid sites are indeed catalytic. Addition of an inorganic Sr oxide base resulted in a linear decrease in the propylene oligomerization conversion at loadings up to 0.3 wt %; while, there is a >95 % loss in conversion above 1 wt % Sr. Additionally, there was a linear decrease in the intensity of the Lewis acid peaks of absorbed pyridine in the IR spectra with an increase in Sr loading, which correlates with the loss in propylene conversion, suggesting that Lewis acid sites are catalytic. Characterization of the Sr structure by XAS and STEM indicates that single Sr2+ ions are bound to the γ-Al2 O3 surface and poison one catalytic site per Sr ion. The maximum loading needed to poison all catalytic sites, assuming uniform surface coverage, was ∼0.4 wt % Sr, giving an acid site density of ∼0.2 sites per nm2 of γ-Al2 O3 , or approximately 3 % of the alumina surface.

Intermetallic alloy structure-activity descriptors derived from inelastic X-ray scattering.

Synchrotron spectroscopy and Density Functional Theory (DFT) are combined to develop a new descriptor for the stability of adsorbed chemical intermediates on metal alloy surfaces. This descriptor probes the separation of occupied and unoccupied d electron density in platinum and is related to shifts in Resonant Inelastic X-ray Scattering (RIXS) signals. Simulated and experimental spectroscopy are directly compared to show that the promoter metal identity controls the orbital shifts in platinum electronic structure. The associated RIXS features are correlated with the differences in the band centers of the occupied and unoccupied d bands, providing chemical intuition for the alloy ligand effect and providing a connection to traditional descriptions of chemisorption. The ready accessibility of this descriptor to both DFT calculations and experimental spectroscopy, and its connection to chemisorption, allow for deeper connections between theory and characterization in the discovery of new catalysts.

MXene-Supported, Atomic-Layered Iridium Catalysts Created by Nanoparticle Re-Dispersion for Efficient Alkaline Hydrogen Evolution.

Tailoring the structure of metal components and interaction with their anchored substrates is essential for improving the catalytic performance of supported metal catalysts; the ideal catalytic configuration, especially down to the range of atomic layers, clusters, and even single atoms, remains a subject under intensive study. Here, an Ir-on-MXene (Mo2 TiC2 Tx ) catalyst with controlled morphology changing from nanoparticles down to flattened atomic layers, and finally ultrathin layers and single atoms dispersed on MXene nanosheets at elevated temperature, is presented. The intermediate structure, consisting of mostly Ir atomic layers, shows the highest activity toward the hydrogen evolution reaction (HER) under industry-compatible alkaline conditions. In addition, the better HER activity of Ir atomic layers than that of single atoms suggests that the former serves as the main active sites. Detailed mechanism analysis reveals that the nanoparticle re-dispersion process and Ir atomic layers with a moderate interaction to the substrate associate with unconventional electron transfer from MXene to Ir, leading to suitable H* adsorption. The results indicate that the structural design is important for the development of highly efficient catalysts.

Atomically precise single-crystal structures of electrically conducting 2D metal-organic frameworks.

Electrically conducting 2D metal-organic frameworks (MOFs) have attracted considerable interest, as their hexagonal 2D lattices mimic graphite and other 2D van der Waals stacked materials. However, understanding their intrinsic properties remains a challenge because their crystals are too small or of too poor quality for crystal structure determination. Here, we report atomically precise structures of a family of 2D π-conjugated MOFs derived from large single crystals of sizes up to 200 µm, allowing atomic-resolution analysis by a battery of high-resolution diffraction techniques. A designed ligand core rebalances the in-plane and out-of-plane interactions that define anisotropic crystal growth. We report two crystal structure types exhibiting analogous 2D honeycomb-like sheets but distinct packing modes and pore contents. Single-crystal electrical transport measurements distinctively demonstrate anisotropic transport normal and parallel to the π-conjugated sheets, revealing a clear correlation between absolute conductivity and the nature of the metal cation and 2D sheet packing motif.

High-Capacitance Pseudocapacitors from Li+ Ion Intercalation in Nonporous, Electrically Conductive 2D Coordination Polymers.

Electrochemical capacitors (ECs) have emerged as reliable and fast-charging electrochemical energy storage devices that offer high power densities. Their use is still limited, nevertheless, by their relatively low energy density. Because high specific surface area and electrical conductivity are widely seen as key metrics for improving the energy density and overall performance of ECs, materials that have excellent electrical conductivities but are otherwise nonporous, such as coordination polymers (CPs), are often overlooked. Here, we report a new nonporous CP, Ni3(benzenehexathiolate) (Ni3BHT), which exhibits high electrical conductivity of over 500 S/m. When used as an electrode, Ni3BHT delivers excellent specific capacitances of 245 F/g and 426 F/cm3 in nonaqueous electrolytes. Structural and electrochemical studies relate the favorable performance to pseudocapacitive intercalation of Li+ ions between the 2D layers of Ni3BHT, a charge-storage mechanism that has thus far been documented only in inorganic materials such as TiO2, Nb2O5, and MXenes. This first demonstration of pseudocapacitive ion intercalation in nonporous CPs, a class of materials comprising thousands of members with distinct structures and compositions, provides important motivation for exploring this vast family of materials for nontraditional, high-energy pseudocapacitors.

Reactivity of (bi-Oxazoline)organonickel Complexes and Revision of a Catalytic Mechanism.

Bi-Oxazoline (biOx) has emerged as an effective ligand framework for promoting nickel-catalyzed cross-coupling, cross-electrophile coupling, and photoredox-nickel dual catalytic reactions. This report fills the knowledge gap of the organometallic reactivity of (biOx)Ni complexes, including catalyst reduction, oxidative electrophile activation, radical capture, and reductive elimination. The biOx ligand displays no redox activity in (biOx)Ni(I) complexes, in contrast to other chelating imine and oxazoline ligands. The lack of ligand redox activity results in more negative reduction potentials of (biOx)Ni(II) complexes and accounts for the inability of zinc and manganese to reduce (biOx)Ni(II) species. On the basis of these results, we revise the formerly proposed "sequential reduction" mechanism of a (biOx)Ni-catalyzed cross-electrophile coupling reaction by excluding catalyst reduction steps.

Carbon Nitride-Based Ruthenium Single Atom Photocatalyst for CO2 Reduction to Methanol.

With increasing concerns for global warming, the solar-driven photocatalytic reduction of CO2 into chemical fuels like methanol is a propitious route to enrich energy supplies, with concomitant reduction of the abundant CO2  stockpiles. Herein, a novel single atom-confinement and a strategy are reported toward single ruthenium atoms dispersion over porous carbon nitride surface. Ruthenium single atom character is well confirmed by EXAFS absorption spectrometric analysis unveiling the cationic coordination environment for the single-atomic-site ruthenium center, that is formed by Ru-N/C intercalation in the first coordination shell, attaining synergism in N-Ru-N connection and interfacial carrier transfer. From time resolved fluorescence decay spectra, the average carrier lifetime of the RuSA-mC3 N4 system is found to be higher compared to m-C3 N4 ; the fact uncovering the crucial role of single Ru atoms in promoting photocatalytic reaction system. A high yield of methanol (1500 µmol g-1 cat. after 6 h of the reaction) using water as an electron donor and the reusability of the developed catalyst without any significant change in the efficiency represent the superior aspects for its potential application in real industrial technologies.

Single Co-Atoms as Electrocatalysts for Efficient Hydrazine Oxidation Reaction.

Single-atom catalysts (SACs) have aroused great attention due to their high atom efficiency and unprecedented catalytic properties. A remaining challenge is to anchor the single atoms individually on support materials via strong interactions. Herein, single atom Co sites have been developed on functionalized graphene by taking advantage of the strong interaction between Co2+ ions and the nitrile group of cyanographene. The potential of the material, which is named G(CN)Co, as a SAC is demonstrated using the electrocatalytic hydrazine oxidation reaction (HzOR). The material exhibits excellent catalytic activity for HzOR, driving the reaction with low overpotential and high current density while remaining stable during long reaction times. Thus, this material can be a promising alternative to conventional noble metal-based catalysts that are currently widely used in HzOR-based fuel cells. Density functional theory calculations of the reaction mechanism over the material reveal that the Co(II) sites on G(CN)Co can efficiently interact with hydrazine molecules and promote the NH bond-dissociation steps involved in the HzOR.

Continuous Electrical Conductivity Variation in M3(Hexaiminotriphenylene)2 (M = Co, Ni, Cu) MOF Alloys.

We report on the continuous fine-scale tuning of band gaps over 0.4 eV and of the electrical conductivity of over 4 orders of magnitude in a series of highly crystalline binary alloys of two-dimensional electrically conducting metal-organic frameworks M3(HITP)2 (M = Co, Ni, Cu; HITP = 2,3,6,7,10,11-hexaiminotriphenylene). The isostructurality in the M3(HITP)2 series permits the direct synthesis of binary alloys (MxM'3-x)(HITP)2 (MM' = CuNi, CoNi, and CoCu) with metal compositions precisely controlled by precursor ratios. We attribute the continuous tuning of both band gaps and electrical conductivity to changes in free-carrier concentrations and to subtle differences in the interlayer displacement or spacing, both of which are defined by metal substitution. The activation energy of (CoxNi3-x)(HITP)2 alloys scales inversely with an increasing Ni percentage, confirming thermally activated bulk transport.

Rapid Electrochemical Methane Functionalization Involves Pd-Pd Bonded Intermediates.

High-valent Pd complexes are potent agents for the oxidative functionalization of inert C-H bonds, and it was previously shown that rapid electrocatalytic methane monofunctionalization could be achieved by electro-oxidation of PdII to a critical dinuclear PdIII intermediate in concentrated or fuming sulfuric acid. However, the structure of this highly reactive, unisolable intermediate, as well as the structural basis for its mechanism of electrochemical formation, remained elusive. Herein, we use X-ray absorption and Raman spectroscopies to assemble a structural model of the potent methane-activating intermediate as a PdIII dimer with a Pd-Pd bond and a 5-fold O atom coordination by HxSO4(x-2) ligands at each Pd center. We further use EPR spectroscopy to identify a mixed-valent M-M bonded Pd2II,III species as a key intermediate during the PdII-to-PdIII2 oxidation. Combining EPR and electrochemical data, we quantify the free energy of Pd dimerization as <-4.5 kcal/mol for Pd2II,III and <-9.1 kcal/mol for PdIII2. The structural and thermochemical data suggest that the aggregate effect of metal-metal and axial metal-ligand bond formation drives the critical Pd dimerization reaction in between electrochemical oxidation steps. This work establishes a structural basis for the facile electrochemical oxidation of PdII to a M-M bonded PdIII dimer and provides a foundation for understanding its rapid methane functionalization reactivity.

Analyzing and Tuning the Chalcogen-Amine-Thiol Complexes for Tailoring of Chalcogenide Syntheses.

The amine-thiol solvent system has been used extensively to synthesize metal chalcogenide thin films and nanoparticles because of its ability to dissolve various metal and chalcogen precursors. While previous studies of this solvent system have focused on understanding the dissolution of metal precursors, here we provide an in-depth investigation of the dissolution of chalcogens, specifically Se and Te. Analytical techniques, including Raman, X-ray absorption, and NMR spectroscopy and high-resolution tandem mass spectrometry, were used to identify pathways for Se and Te dissolution in butylamine-ethanethiol and ethylenediamine-ethanethiol solutions. Se in monoamine-monothiol solutions was found to form ionic polyselenides free of thiol ligands, while in diamine-monothiol solutions, thiol coordination with polyselenides was predominately observed. When the relative concentration of thiol is increased to that of Se, the chain length of polyselenide species was observed to shorten. Analysis of Te dissolution in diamine-thiol solutions also suggested the formation of relatively unstable thiol-coordinated Te ions. This instability of Te ions was found to be reduced by codissolving Te with Se in diamine-thiol solutions. Analysis of the codissolved solutions revealed the presence of atomic interaction between Se and Te through the identification of Se-Te bonds. This new understanding then provided a new route to dissolve otherwise insoluble Te in butylamine-ethanethiol solutions by taking advantage of the Se2- nucleophile. Finally, the knowledge gained for chalcogen dissolutions in this solvent system allowed for controlled alloying of Se and Te in PbSenTe1-n material and also provided a general knob to alter various metal chalcogenide material syntheses.

Diffusion-Limited Formation of Nonequilibrium Intermetallic Nanophase for Selective Dehydrogenation.

Nonequilibrium intermetallic phases in the nanoscale were realized by diffusion-controlled solid-state transformation, forming SiO2 supported NPs with Pd core and a CsCl type Pd1M1 shell, where M is Sn or Sb. The core-shell geometry is identified from scanning transmission electron microscopy and infrared spectroscopy and the crystal structure is confirmed from in situ synchrotron X-ray diffraction and X-ray absorption spectroscopy. The highly symmetric Pd1M1 intermetallic phase has not been reported previously and contains catalytic ensembles with high selectivity toward dehydrogenation of propane. The kinetically limited solid-state reaction is generally applicable to nanoparticle synthesis and could produce materials with desired structures and properties beyond conventional structural limits.

In Situ Formed Pt3Ti Nanoparticles on a Two-Dimensional Transition Metal Carbide (MXene) Used as Efficient Catalysts for Hydrogen Evolution Reactions.

The design of efficient catalysts capable of delivering high currents at low overpotentials for hydrogen evolution reactions (HERs) is urgently needed to use catalysts in practical applications. Herein, we report platinum (Pt) alloyed with titanium (Ti) from the surface of Ti3C2Tx MXenes to form Pt3Ti intermetallic compound (IMC) nanoparticles (NPs) via in situ coreduction. In situ X-ray absorption spectroscopy (XAS) indicates that Pt undergoes a temperature-dependent transformation from single atoms to intermetallic compounds, and the catalyst reduced at 550 °C exhibits a superior HER performance in acidic media. The Pt/Ti3C2Tx-550 catalyst outperforms commercial Pt/Vulcan and has a small overpotential of 32.7 mV at 10 mA cm-2 and a low Tafel slope of 32.3 mV dec-1. The HER current was normalized by the mass and dispersion of Pt, and the mass activity and specific activity of Pt/Ti3C2Tx-550 are 4.4 and 13 times higher, respectively, than those of Pt/Vulcan at an overpotential of 70 mV. The density functional theory (DFT) calculations suggest that the (111)- and (100)-terminated Pt3Ti nanoparticles exhibit *H binding comparable to Pt(111), while the (110) termination has an *H adsorption that is too exergonic, thus poisoned in the low overpotential region. This work demonstrates the potential of MXenes as platforms for the design of electrocatalysts and may spur future research for other MXene-supported metal catalysts that can be used for a wide range of electrocatalytic reactions.

Operando Spectroscopic and Kinetic Characterization of Aerobic Allylic C-H Acetoxylation Catalyzed by Pd(OAc)2/4,5-Diazafluoren-9-one.

Allylic C-H acetoxylations are among the most widely studied palladium(II)-catalyzed C-H oxidation reactions. While the principal reaction steps are well established, key features of the catalytic mechanisms are poorly characterized, including the identity of the turnover-limiting step and the catalyst resting state. Here, we report a mechanistic study of aerobic allylic acetoxylation of allylbenzene with a catalyst system composed of Pd(OAc)2 and 4,5-diazafluoren-9-one (DAF). The DAF ligand is unique in its ability to support aerobic catalytic turnover, even in the absence of benzoquinone or other co-catalysts. Herein, we describe operando spectroscopic analysis of the catalytic reaction using X-ray absorption and NMR spectroscopic methods that allow direct observation of the formation and decay of a palladium(I) species during the reaction. Kinetic studies reveal the presence of two distinct kinetic phases: (1) a burst phase, involving rapid formation of the allylic acetoxylation product and formation of the dimeric PdI complex [PdI(DAF)(OAc)]2, followed by (2) a post-burst phase that coincides with evolution of the catalyst resting state from the PdI dimer into a π-allyl-PdII species. The data provide unprecedented insights into the role of ancillary ligands in supporting catalytic turnover with O2 as the stoichiometric oxidant and establish an important foundation for the development of improved catalysts for allylic oxidation reactions.

Designing Highly Efficient and Long-Term Durable Electrocatalyst for Oxygen Evolution by Coupling B and P into Amorphous Porous NiFe-Based Material.

Oxygen evolution reaction (OER) is of great significance for hydrogen production via water electrolysis, which, however, demands development of highly active, durable, and cost-effective electrocatalysts in order to stride into a renewable energy era. Herein, highly efficient and long-term durable OER by coupling B and P into an amorphous porous NiFe-based electrocatalyst is reported, which possesses an amorphous porous metallic bulk structure and high corrosion resistance, and overcomes the issues associated with currently used catalyst nanomaterials. The PB codoping in the activated NiFePB (a-NiFePB) delocalizes both Fe and Ni at Fermi energy level and enhances p-d hybridization as simulated by density functional theory calculations. The harmonized electronic structure and unique porous framework of the a-NiFePB consequently improve the OER activity. The activated NiFePB thus exhibits an extraordinarily low overpotential of 197 mV for harvesting 10 mA cm-2 OER current density and 233 mV for reaching 100 mA cm-2 under chronopotentiometry condition, with the Tafel slope harmoniously conforming to 34 mV dec-1 . Impressive long-term stability of this new catalyst is evidenced by only limited activity decay after 1400 h operation at 100 mA cm-2 . This work strategically directs a way for heading up a promising energy conversion alternative.

Publisher Correction: A molecular cross-linking approach for hybrid metal oxides.

In the version of this Article originally published, Liban M. A. Saleh was incorrectly listed as Liban A. M. Saleh due to a technical error. This has now been amended in all online versions of the Article.

A molecular cross-linking approach for hybrid metal oxides.

There is significant interest in the development of methods to create hybrid materials that transform capabilities, in particular for Earth-abundant metal oxides, such as TiO2, to give improved or new properties relevant to a broad spectrum of applications. Here we introduce an approach we refer to as 'molecular cross-linking', whereby a hybrid molecular boron oxide material is formed from polyhedral boron-cluster precursors of the type [B12(OH)12]2-. This new approach is enabled by the inherent robustness of the boron-cluster molecular building block, which is compatible with the harsh thermal and oxidizing conditions that are necessary for the synthesis of many metal oxides. In this work, using a battery of experimental techniques and materials simulation, we show how this material can be interfaced successfully with TiO2 and other metal oxides to give boron-rich hybrid materials with intriguing photophysical and electrochemical properties.

Strong Electronic Coupling of Molecular Sites to Graphitic Electrodes via Pyrazine Conjugation.

Glassy carbon electrodes were functionalized with redox-active moieties by condensation of o-phenylenediamine derivatives with o-quinone sites native to graphitic carbon surfaces. Electrochemical and spectroscopic investigations establish that these graphite-conjugated catalysts (GCCs) exhibit strong electronic coupling to the electrode, leading to electron transfer (ET) behavior that diverges fundamentally from that of solution-phase or surface-tethered analogues. We find that (1) ET is not observed between the electrode and a redox-active GCC moiety regardless of applied potential. (2) ET is observed at GCCs only if the interfacial reaction is ion-coupled. (3) Even when ET is observed, the oxidation state of a transition metal GCC site remains unchanged. From these observations, we construct a mechanistic model for GCC sites in which ET behavior is identical to that of catalytically active metal surfaces rather than to that of molecules in solution. These results suggest that GCCs provide a versatile platform for bridging molecular and heterogeneous electrocatalysis.

Changes in Catalytic and Adsorptive Properties of 2 nm Pt3Mn Nanoparticles by Subsurface Atoms.

Supported multimetallic nanoparticles (NPs) are widely used in industrial catalytic processes, where the relation between surface structure and function is well-known. However, the effect of subsurface layers on such catalysts remains mostly unstudied. Here, we demonstrate a clear subsurface effect on supported 2 nm core-shell NPs with atomically precise and high temperature stable Pt3Mn intermetallic surface measured by in situ synchrotron X-ray Diffraction, difference X-ray Absorption Spectroscopy, and Energy Dispersive X-ray Spectroscopy. The NPs with a Pt3Mn subsurface have 98% selectivity to C-H over C-C bond activation during propane dehydrogenation at 550 °C compared with 82% for core-shell NPs with a Pt subsurface. The difference is correlated with significant reduction in the heats of reactant adsorption due to the Pt3Mn intermetallic subsurface as discerned by theory as well as experiment. The findings of this work highlight the importance of subsurface for supported NP catalysts, which can be tuned via controlled intermetallic formation. Such approach is generally applicable to modifying multimetallic NPs, adding another dimension to the tunability of their catalytic performance.