Trace Thiol Moieties in the Ligand Layer Induce Superior Catalytic Gold Nanoclusters.

We here show that the typical poison of thiols, if below a certain level, promotes rather than suppresses the catalytic activity of gold nanoclusters (AuNCs). A few thiol groups functionalized hyperbranched polyethylenimine (PEI, Mn = 2000 Da) patched on a mesoporous polymeric bead aid the direct synthesis of AuNCs. The nucleation efficiency of AuNC is 93-fold favored at a level of 2 thiols per PEI (0.04 equiv of the amino units) than that by neat PEI, and AuNCs (1.3 nm) are obtained up to a gold load of 6.3% on the support. Unexpectedly, the catalytic activity of AuNCs is favored by the thiol up to 2 thiols per PEI, as evaluated from the surface-normalized rate constant of the model reaction of 4-nitrophenol-reduction. The catalytic promotion by thiols probably stems from optimized electron density on AuNC. If the residual NH groups of PEI were further fully treated with glycidyltrimethylammonium chloride, the catalytic activity is again enhanced, where the accelerated mass transfer is responsible for the promotion. Overall, the catalytic activity reaches an unprecedented value (metal-normalized rate constant kc = 29.4 L mmol-1 s-1 and turnover frequency = 1623 h-1, as evaluated with the model reaction of 4-nitrophenol reduction) ever reported for supported AuNCs. Our results suggest that orthogonal ligand optimization is an effective manner of triggering the release of the catalytic potential of AuNCs, among which thiol is unique.

Customizing a Hyperbranched Ligand Confers Supported Platinum Nanoclusters with Unexpected Catalytic Activity toward the Reduction of 4-Nitrophenol.

We here show that a dendritic molecule combined with ligand merit confers supported platinum nanoclusters (PtNCs) with unprecedented catalytic performance. Branched polyethylenimine (PEI, Mn = 2000 D) patched on a porous bead is modified with 2-(diphenylphosphino)benzaldehyde (dppb) before being used to mediate a platinum nanoparticle/nanocluster (Pt0). The catalytic activity of Pt0 toward the reduction of 4-nitrophenol (4-NP) is evaluated from the parameter of Pt-normalized rate constant (kc). Optimization of the dppb level along with transformation of the PEI hydrogens into diol or trimethylammonium groups imparts supported Pt0 unprecedented activity (kc = 19.2 L mmol-1 s-1 and turnover frequency (TOF) = 1041 h-1). The supported Pt0 at an extremely low dosage of 0.1 ppm promotes 98% conversion of 4-NP within minutes and is well recyclable. The striking catalytic activity is attributed to the combination of orthogonal ligand properties such as weak ligand nature, catalyst-activating ability, excellent substrate affinity, and effect on PtNC-size mediation of the ligand.

Simple Approximation for the Ideal Reference State of Gases Adsorbed on Solid-State Surfaces.

Reference states are useful as models for facilitating calculations of equilibrium constants, and they may also serve as standard states that are convenient for organizing and tabulating thermodynamic data; however, standard state conventions and appropriate reference states for adsorbed species have received less attention than those for pure substances and solutes. Here, we compare seven choices of reference states for calculations of equilibrium constants and transition state theory rate constants for flat surfaces, in particular (1) an ideal 2D harmonic oscillator, (2) an ideal rigid-molecule harmonic oscillator, (3) an ideal 2D harmonic oscillator with separable surface modes, (4) a 2D ideal gas, (5) an ideal 2D hindered translator, (6) an ideal 2D hindered translator with lowest-order barriers, and (7) a simple ideal 2D hindered translator proposed in this work. The advantage of models 5-7 is that they can treat both mobile and localized adsorbates in a consistent way, whereas models 1-3 are only appropriate for localized adsorbates, and model 4 is only appropriate for a freely translating adsorbate. Furthermore, models 6 and 7 reduce the computational cost without the user having to calculate barrier heights for diffusion. An advantage of the simple ideal 2D hindered translator is that it has a physical high-temperature limit. We also propose a reference state for nonflat surfaces. The user is encouraged to choose a reference state based on the appropriateness of the model and the practicality of the calculations.

Enhanced Crystallinity of Covalent Organic Frameworks Formed Under Physical Confinement by Exfoliated Graphene.

The polymerization of 1,4-benzenediboronic acid (BDBA) on mica to form a covalent organic framework (COF-1) reveals a dramatic increase in crystallinity when physically confined by exfoliated graphene. COF-1 domains formed under graphene confinement are highly geometric in shape and on the order of square micrometers in size, while outside of the exfoliated flakes, the COF-1 does not exhibit long-range mesoscale structural order, according to atomic force microscopy imaging. Micro-Fourier transform infrared spectroscopy confirms the presence of COF-1 both outside and underneath the exfoliated graphene flakes, and density functional theory calculations predict that higher mobility and self-assembly are not causes of this higher degree of crystallinity for the confined COF-1 domains. The most likely origin of the confined COF-1's substantial increase in crystallinity is from enhanced dynamic covalent crystallization due to the water confined beneath the graphene flake.

Nanoelectrochemistry Reveals Selective Interactions of Perfluoroalkyl Substances (PFASs) with Silver Nanoparticles.

Nanoelectrochemistry allows for the investigation of the interaction of per- and polyfluoroalkyl substances (PFASs) with silver nanoparticles (AgNPs) and the elucidation of the binding behaviour of PFASs to nanoscale surfaces with high sensitivity. Mechanistic studies supported by single particle collision electrochemistry (SPCE), spectroscopic and density functional theory (DFT) calculations indicate the capability of polyfluorooctane sulfonic acid (PFOS), a representative PFAS, to selectively bind and induce aggregation of AgNPs. Single-particle measurements provide identification of the "discrete" AgNPs agglomeration (e.g. 2-3 NPs) formed through the inter-particles F-F interactions and the selective replacement of the citrate stabilizer by the sulfonate of the PFOS. Such interactions are characteristic only for long chain PFAS (-SO3 - ) providing a means to selectively identify these substances down to ppt levels. Measuring and understanding the interactions of PFAS at nanoscale surfaces are crucial for designing ultrasensitive methods for detection and for modelling and predicting their interaction in the environment.

Screening and identification of serum biomarkers of osteoarticular tuberculosis based on mass spectrometry.

BACKGROUND: In view of the current difficulty of clinically diagnosing osteoarticular tuberculosis, our aim was to use mass spectrometry to establish diagnostic models and to screen and identify serum proteins which could serve as potential diagnostic biomarkers for early detection of osteoarticular tuberculosis. METHODS: Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was used to select an osteoarticular tuberculosis-specific serum peptide profile and establish diagnostic models. Further, liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to identify potential serum biomarkers that could be used for auxiliary diagnosis of osteoarticular tuberculosis, and then clinical serum samples were used to verify these biomarkers by enzyme-linked immunosorbent assay (ELISA). RESULTS: We established four diagnostic models that can distinguish osteoarticular tuberculosis from rheumatoid arthritis, ankylosing spondylitis, osteoarticular infections, and healthy adults. The models were osteoarticular tuberculosis-rheumatoid arthritis, osteoarticular tuberculosis-ankylosing spondylitis, osteoarticular tuberculosis-osteoarticular infections, and osteoarticular tuberculosis-healthy adult, and their accuracy was 76.78%, 79.02%, 83.77%, and 88.16%, respectively. Next, we selected and identified 18 proteins, including complement factor H-related protein 1 (CFHR1) and complement factor H-related protein 2 (CFHR2), which were upregulated in the tuberculosis group only. CONCLUSIONS: We successfully established four diagnostic models involving osteoarticular tuberculosis, rheumatoid arthritis, ankylosing spondylitis, osteoarticular infections, and healthy adults. Furthermore, we found that CFHR1 and CFHR2 may be two valuable auxiliary diagnostic indicators for osteoarticular tuberculosis. These results provide reference values for rapid and accurate diagnosis of osteoarticular tuberculosis.

Selective Methane Oxidation to Methanol on Cu-Oxo Dimers Stabilized by Zirconia Nodes of an NU-1000 Metal-Organic Framework.

Mononuclear and dinuclear copper species were synthesized at the nodes of an NU-1000 metal-organic framework (MOF) via cation exchange and subsequent oxidation at 200 °C in oxygen. Copper-exchanged MOFs are active for selectively converting methane to methanol at 150-200 °C. At 150 °C and 1 bar methane, approximately a third of the copper centers are involved in converting methane to methanol. Methanol productivity increased by 3-4-fold and selectivity increased from 70% to 90% by increasing the methane pressure from 1 to 40 bar. Density functional theory showed that reaction pathways on various copper sites are able to convert methane to methanol, the copper oxyl sites with much lower free energies of activation. Combining studies of the stoichiometric activity with characterization by in situ X-ray absorption spectroscopy and density functional theory, we conclude that dehydrated dinuclear copper oxyl sites formed after activation at 200 °C are responsible for the activity.

Beyond the Active Site: Tuning the Activity and Selectivity of a Metal-Organic Framework-Supported Ni Catalyst for Ethylene Dimerization.

To modify its steric and electronic properties as a support for heterogeneous catalysts, electron-withdrawing and electron-donating ligands, hexafluoroacetylacetonate (Facac-) and acetylacetonate (Acac-), were introduced to the metal-organic framework (MOF), NU-1000, via a process akin to atomic layer deposition (ALD). In the absence of Facac- or Acac-, NU-1000-supported, AIM-installed Ni(II) sites yield a mixture of C4, C6, C8, and polymeric products in ethylene oligomerization. (AIM = ALD-like deposition in MOFs). In contrast, both Ni-Facac-AIM-NU-1000 and Ni-Acac-AIM-NU-1000 exhibit quantitative catalytic selectivity for C4 species. Experimental findings are supported by density functional theory calculations, which show increases in the activation barrier for the C-C coupling step, due mainly to rearrangement of the siting of Facac- or Acac- to partially ligate added nickel. The results illustrate the important role of structure-tuning support modifiers in controlling the activity of MOF-sited heterogeneous catalysts and in engendering catalytic selectivity. The results also illustrate the ease with which crystallographically well-defined modifications of the catalyst support can be introduced when the node-coordinating molecular modifier is delivered via the vapor phase.

Well-Defined Rhodium-Gallium Catalytic Sites in a Metal-Organic Framework: Promoter-Controlled Selectivity in Alkyne Semihydrogenation to E-Alkenes.

Promoters are ubiquitous in industrial heterogeneous catalysts. The wider roles of promoters in accelerating catalysis and/or controlling selectivity are, however, not well understood. A model system has been developed where a heterobimetallic active site comprising an active metal (Rh) and a promoter ion (Ga) is preassembled and delivered onto a metal-organic framework (MOF) support, NU-1000. The Rh-Ga sites in NU-1000 selectively catalyze the hydrogenation of acyclic alkynes to E-alkenes. The overall stereoselectivity is complementary to the well-known Lindlar's catalyst, which generates Z-alkenes. The role of the Ga in promoting this unusual selectivity is evidenced by the lack of semihydrogenation selectivity when Ga is absent and only Rh is present in the active site.

A Bimetallic Nickel-Gallium Complex Catalyzes CO2 Hydrogenation via the Intermediacy of an Anionic d10 Nickel Hydride.

Large-scale CO2 hydrogenation could offer a renewable stream of industrially important C1 chemicals while reducing CO2 emissions. Critical to this opportunity is the requirement for inexpensive catalysts based on earth-abundant metals instead of precious metals. We report a nickel-gallium complex featuring a Ni(0)→Ga(III) bond that shows remarkable catalytic activity for hydrogenating CO2 to formate at ambient temperature (3150 turnovers, turnover frequency = 9700 h-1), compared with prior homogeneous Ni-centered catalysts. The Lewis acidic Ga(III) ion plays a pivotal role in stabilizing catalytic intermediates, including a rare anionic d10 Ni hydride. Structural and in situ characterization of this reactive intermediate support a terminal Ni-H moiety, for which the thermodynamic hydride donor strength rivals those of precious metal hydrides. Collectively, our experimental and computational results demonstrate that modulating a transition metal center via a direct interaction with a Lewis acidic support can be a powerful strategy for promoting new reactivity paradigms in base-metal catalysis.

Bridging Zirconia Nodes within a Metal-Organic Framework via Catalytic Ni-Hydroxo Clusters to Form Heterobimetallic Nanowires.

Metal-organic frameworks (MOFs), with their well-ordered pore networks and tunable surface chemistries, offer a versatile platform for preparing well-defined nanostructures wherein functionality such as catalysis can be incorporated. Notably, atomic layer deposition (ALD) in MOFs has recently emerged as a versatile approach to functionalize MOF surfaces with a wide variety of catalytic metal-oxo species. Understanding the structure of newly deposited species and how they are tethered within the MOF is critical to understanding how these components couple to govern the active material properties. By combining local and long-range structure probes, including X-ray absorption spectroscopy, pair distribution function analysis, and difference envelope density analysis, with electron microscopy imaging and computational modeling, we resolve the precise atomic structure of metal-oxo species deposited in the MOF NU-1000 through ALD. These analyses demonstrate that deposition of NiOxHy clusters occurs selectively within the smallest pores of NU-1000, between the zirconia nodes, serving to connect these nodes along the c-direction to yield heterobimetallic metal-oxo nanowires. This bridging motif perturbs the NU-1000 framework structure, drawing the zirconia nodes closer together, and also underlies the sintering resistance of these clusters during the hydrogenation of light olefins.

Spin Crossover and Exchange Effects on Oxygen Evolution Reaction Catalyzed by Bimetallic Metal Organic Frameworks.

Bimetallic metal-organic frameworks (BMOFs) have shown a superior oxygen evolution reaction (OER) performance, attributed to the synergistic effects of dual metal sites. However, the significant role of these dual-metal synergies in the OER is not yet fully understood. In this study, we employed density functional theory to systematically investigate the OER performance of NiAl- and NiFe-based BMOFs by examining all possible spin states of each intermediate across diverse external potentials and pH environments. We found that the spin state featuring a shallow hole trap state and Ni ions with a higher oxidation state serve as strong oxidizing agents, promoting the OER. An external potential-induced spin crossover was observed in each intermediate, resulting in significant changes in the overall reaction and activation energies due to altered energy levels. Combining the constant potential method and the electrochemical nudged elastic band method, we mapped the minimum free energy barriers of the OER under varied external potential and pH by considering the spin crossover effect for both NiAl and NiFe BMOFs. The results showed that NiFe exhibits better OER thermodynamics and kinetics, which is in good agreement with experimentally measured OER polarization curves and Tafel plots. Moreover, we found that the improved OER kinetics of NiFe not only is attributed to lower barriers but also is a result of improved electrical conductivity arising from the synergistic effects of Ni-Fe dual-metal sites. Specifically, replacing the second metal Al with Fe leads to two significant outcomes: a reduction in both the band gap and the effective hole mass compared to NiAl, and the initiation of super- and double-exchange interactions within the Ni-F-Fe chain, thereby enhancing electron transfer and hopping and leading to the improved OER kinetics.

Imaging reactions of acetone with oxygen adatoms on partially oxidized TiO2(110).

Understanding the interaction of O2 with ketones on metal oxide surfaces is important for the photo-oxidation of toxic organic molecules. The consecutive reaction steps of acetone molecules with oxygen adatoms (Oa's) on partially oxidized TiO2(110) surfaces have been studied using high-resolution scanning tunneling microscopy (STM) at 300 K. The sequential isothermal STM images reveal two types of acetone-Oa species as a result of reactions of acetone with an oxygen adatom and a bridging bound oxygen vacancy (V(O)). One such species is the Ti5c-bound acetone-Oa diolate formed from Ti5c-bound acetone reacting with Oa. The diolate is mobile at 300 K and can assist the diffusion of surface Oa by exchanging the acetone oxygen with the Oa. The second acetone-Oa species is the V(O)-bound acetone-Oa complex formed from a V(O)-bound acetone reacting with an Oa located on the neighboring Ti row. The V(O)-bound complex is stationary at 300 K. This species has not been reported previously.

Metal/metal-oxide interface catalysed thermal and electrochemical CO2 conversion: a perspective from DFT-based studies.

Converting CO2 to valuable chemicals through a variety of thermal, photo-, and electro-catalytic reaction processes will reduce the net CO2 emission and contribute positively to the "net-zero" goal. C1 and C2 products are important chemical feedstocks and can be produced from the effective catalytic conversion of CO2. The key to developing effective CO2 conversion catalysts is an understanding of CO2 interaction and the elementary bond-breaking and formation steps on the active catalysts. Over the past two decades, density functional theory-based approaches have enabled both mechanistic understanding and catalyst design for CO2 activation and conversion. In this article, we review our recent effort in understanding the mechanism of CO2 activation and conversion, focusing on the unique role of the metal/metal oxide interfaces in both thermal and electrochemical catalytic CO2 reduction. We showed that In2O3-based catalysts exhibited a uniquely high methanol selectivity while suppressing CO formation from the reverse water-gas shift reaction. We have also demonstrated that the metal/metal-oxide interfaces can be tuned by selecting an appropriate metal and metal oxide to optimize its activity and selectivity for both thermal- and electro-catalytic reduction of CO2. The oxophilicity of the metal in the metal oxide can be used as a qualitative measure for determining the selectivity towards CH3OH or CH4 in the electro-catalytic reduction of CO2. The studies demonstrated the impact of the density functional theory-based atomic-level approaches in unravelling the reaction mechanism and predicting highly efficient catalysts and catalytic systems.

Several potential serum proteomic biomarkers for diagnosis of osteoarticular tuberculosis based on mass spectrometry.

BACKGROUND: Osteoarticular tuberculosis is one of the extrapulmonary tuberculosis (EPTB) diseases, which is mainly caused by infection of Mycobacterium tuberculosis (MTB) in bone and joints. The limitation of current clinical test methods is leading to a high misdiagnosis rate and affecting the treatment and prognosis. This study aims to search serum biomarkers that can assist in the diagnosis of osteoarticular tuberculosis. METHODS: Proteomics can serve as an important method in the discovery of disease biomarkers. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to analyze proteins in 90 serum samples, which were collected from June 2020 to December 2021, then evaluated by statistical analysis to screen potential biomarkers. After that, potential biomarkers were validated by enzyme-linked immunosorbent assay (ELISA) and diagnostic models were also established for observation of multi-index diagnostic efficacy. RESULTS: 118 differential expressed proteins (DEPs) were obtained in serum after statistical analysis. After the diagnostic efficacy evaluation and clinical verification, inter-alpha-trypsin inhibitor heavy chain H2 (ITIH2), complement factor H-related protein 2 (CFHR2), complement factor H-related protein 3 (CFHR3), and complement factor H-related protein 5 (CFHR5) were found as potential biomarkers, with 0.7167 (95 %CI: 0.5846-0.8487), 0.8600 (95 %CI: 0.7701-0.9499), 0.8150 (95 %CI: 0.6998-0.9302), and 0.9978 (95 %CI: 0.9918-1.0040) AUC value, respectively. The remaining DEPs except CFHR5 were constructed as diagnostic models, the diagnostic model contained CFHR2 and CFHR3 had good diagnostic efficacy with 0.942 (95 %CI: 0.872-0.980) AUC value compared to other models. CONCLUSION: This study provides a reference for the discovery of serum protein markers for osteoarticular tuberculosis diagnosis, and the screened DEPs can also provide directions for subsequent pathogenesis research.

Tunability of band gaps in metal-organic frameworks.

The tunability of the band gaps in Zn-based metal-organic frameworks (MOFs) has been experimentally demonstrated via two different approaches: changing the cluster size of the secondary building unit (SBU) or alternating the conjugation of the organic linker.

A DFT study of methanol dehydrogenation on the PdIn(110) surface.

Methanol decomposition to CO and H(2) on PdIn(110) has been studied by following the sequential dehydrogenation steps from CH(3)OH → CH(3)O → CH(2)O → CHO → CO using density functional theory slab calculations. The first three of the four elementary steps are strongly endothermic. The last step, i.e., CHO → CO + H, is almost thermal neutral. We also examined the effect of considering van der Waals interaction on the reaction energy and activation barrier of each elementary step by using the optB88-vdW and optB86b-vdW functionals. Our results show that both overall reaction energy and activation barrier were reduced by including van der Waals interactions but the qualitative picture remains unchanged.

Novel Potential Diagnostic Serum Biomarkers of Metabolomics in Osteoarticular Tuberculosis Patients: A Preliminary Study.

Osteoarticular tuberculosis is one of the extrapulmonary tuberculosis, which is mainly caused by direct infection of Mycobacterium tuberculosis or secondary infection of tuberculosis in other parts. Due to the low specificity of the current detection method, it is leading to a high misdiagnosis rate and subsequently affecting the follow-up treatment and prognosis. Metabolomics is mainly used to study the changes of the body's metabolites in different states, so it can serve as an important means in the discovery of disease-related metabolic biomarkers and the corresponding mechanism research. Liquid chromatography tandem mass spectrometry (LC-MS/MS) was used to detect and analyze metabolites in the serum with osteoarticular tuberculosis patients, disease controls, and healthy controls to find novel metabolic biomarkers that could be used in the diagnosis of osteoarticular tuberculosis. Our results showed that 68 differential metabolites (p<0.05, fold change>1.0) were obtained in osteoarticular tuberculosis serum after statistical analysis. Then, through the evaluation of diagnostic efficacy, PC[o-16:1(9Z)/18:0], PC[20:4(8Z,11Z,14Z,17Z)/18:0], PC[18:0/22:5(4Z,7Z,10Z,13Z,16Z)], SM(d18:1/20:0), and SM[d18:1/18:1(11Z)] were found as potential biomarkers with high diagnostic efficacy. Using bioinformatics analysis, we further found that these metabolites share many lipid metabolic signaling pathways, such as choline metabolism, sphingolipid signaling, retrograde endocannabinoid signaling, and sphingolipid and glycerophospholipid metabolism; these results suggest that lipid metabolism plays an important role in the pathological process of tuberculosis. This study can provide certain reference value for the study of metabolic biomarkers of osteoarticular tuberculosis and the mechanism of lipid metabolism in osteoarticular tuberculosis and even other tuberculosis diseases.

Copper-zirconia interfaces in UiO-66 enable selective catalytic hydrogenation of CO2 to methanol.

Molecular interactions with both oxides and metals are essential for heterogenous catalysis, leading to remarkable synergistic impacts on activity and selectivity. Here, we show that the direct link between the two phases (and not merely being together) is required to selectively hydrogenate CO2 to methanol on catalysts containing Cu and ZrO2. Materials consisting of isolated Cu particles or atomically dispersed Cu-O-Zr sites only catalyze the reverse water-gas shift reaction. In contrast, a metal organic framework structure (UiO-66) with Cu nanoparticles occupying missing-linker defects maximizes the fraction of metallic Cu interfaced to ZrO2 nodes leading to a material with high adsorption capacity for CO2 and high activity and selectivity for low-temperature methanol synthesis.

Thermodynamic and kinetic studies of H2 and N2 binding to bimetallic nickel-group 13 complexes and neutron structure of a Ni(η2-H2) adduct.

Understanding H2 binding and activation is important in the context of designing transition metal catalysts for many processes, including hydrogenation and the interconversion of H2 with protons and electrons. This work reports the first thermodynamic and kinetic H2 binding studies for an isostructural series of first-row metal complexes: NiML, where M = Al (1), Ga (2), and In (3), and L = [N(o-(NCH2PiPr2)C6H4)3]3-. Thermodynamic free energies (ΔG°) and free energies of activation (ΔG ‡) for binding equilibria were obtained via variable-temperature 31P NMR studies and lineshape analysis. The supporting metal exerts a large influence on the thermodynamic favorability of both H2 and N2 binding to Ni, with ΔG° values for H2 binding found to span nearly the entire range of previous reports. The non-classical H2 adduct, (η2-H2)NiInL (3-H2), was structurally characterized by single-crystal neutron diffraction-the first such study for a Ni(η2-H2) complex or any d10 M(η2-H2) complex. UV-Vis studies and TD-DFT calculations identified specific electronic structure perturbations of the supporting metal which poise NiML complexes for small-molecule binding. ETS-NOCV calculations indicate that H2 binding primarily occurs via H-H σ-donation to the Ni 4p z -based LUMO, which is proposed to become energetically accessible as the Ni(0)→M(iii) dative interaction increases for the larger M(iii) ions. Linear free-energy relationships are discussed, with the activation barrier for H2 binding (ΔG ‡) found to decrease proportionally for more thermodynamically favorable equilibria. The ΔG° values for H2 and N2 binding to NiML complexes were also found to be more exergonic for the larger M(iii) ions.