Hydrogenation Catalysis by Hydrogen Spillover on Platinum-Functionalized Heterogeneous Boronic Acid-Polyoxometalates

Tailored electronic interaction between metal-support trigger reverse hydrogen spillover for efficient hydrogen evolution

The triggering of fast hydrogen spillover through regulating the charge rearrangement of the metal-support serves as a crucial mechanism for decoupling the activity of HER catalysts from the adsorption properties, which not only contributes to enhancing the performance of the catalysts but also facilitates the production of green hydrogen. Herein, we tailor the electronic interaction between two-dimensional (2D) nitrogen-doped MoC (N-MoC) nanosheets and anultra-low content of Pt nanoclusters (1 wt%) to trigger reverse hydrogen spillover and modulate the electronic structure of Pt, thus achieving efficient and stable HER. Compared to Pt/C (0.229 A mgPt-1), Pt/N-MoC demonstrates a mass activity of 12.945 A mgPt-1, representing an enhancement of nearly 57.5 times. Notably, the excellent electrocatalytic performance was verified in the proton exchange membrane water electrolyzer configuration. Combining experimental and theoretical analysis, anultra-low load of Pt nanocluster (1 wt%) integrated with N-MoC nanosheets can induce a charge transfer from N-MoC to Pt, thus modulating the d-band center of Pt to improve the hydrogen adsorption properties and achieving fast hydrogen desorption (ΔG = 0.019 eV); furthermore, a small difference in work function between Pt nanoclusters and the N-MoC were achieved to dilute charge accumulation between the metal-support interface, thus reducing the energy barrier of hydrogen spillover.

Lanthanide-Incorporated PIII-SbIII-Heteroatom-Templated Tetrahedral Heteropolyoxometalate Cluster for Detecting Early Tumor Marker MicroRNA-155

Heteropolyoxometalates have garnered widespread attention owing to their diverse structures and intriguing physicochemical properties. Herein, we successfully synthesized a unique lanthanide-incorporated PIII-SbIII-heteroatom-templated tetrahedral polyoxometalate cluster [H2N(CH3)2]20Na7H7{[Er6(H2O)6][W4O16][HPSbW15O54]4}·132H2O (1). The polyoxoanion of 1 can be perceived as four trilacunary Dawson [HPSbW15O54]11- {PSbW15} building blocks encapsulating a deca-nuclear heterometallic [Er6(H2O)6W4O16]10+ cluster. This heterometallic cluster comprises an inner tetrahedral [W4O16]8- ({W4}) core surrounded by an octahedral [Er6(H2O)6]18+ ({Er6}) shell. Consequently, the polyoxoanion of 1 exhibits the distinctive ({W4} ⊂ {Er6} ⊂ [{PSbW15}]4) three-shell structure. Considering the electron transfer characteristics of 1, it was coelectropolymerized with N-methylpyrrole (NMPy) to fabricate the 1-PNMPy film (PNMPy = polyNMPy). Notably, the incorporation of 1 improves the electron distribution within the PNMPy backbone, thereby narrowing the band gap of PNMPy and enhancing the conductive performance of the 1-PNMPy film. Therefore, the 1-PNMPy film is utilized as the modified electrode material to construct an electrochemical biosensor for the sensitive detection of the tumor marker microRNA-155. This research not only provides a viable approach for the fabrication of multishell heteropolyoxometalates but also promotes the exploration and application of multicomposition polyoxometalates in electrochemical biosensing microRNA.

In Situ Growth of Metal-Organic Layer on Polyoxometalate-etching Cu2O to Boost CO2 Reduction with High Stability

Low-cost Cu2O with a suitable band gap holds great potential for solar utilization. However severe photocorrosion and weak CO2 capture capability have significantly hindered their application in artificial photosynthesis. Herein, polyoxometalate (POM)-etching and in situ growth of metal-organic framework (MOF) can simultaneously incorporate electron-sponge and HKUST protective layer into Cu2O. The resulting ternary composites Cu2O@POM@HKUST-n (POM=PMo12O40 and PW12O40) with dual hetero-interfaces can efficiently convert CO2 to HCOOH with 5226 μmol g-1 yield, over 5 and 55 times higher than that of Cu2O (1010 μmol g-1) and Cu2O@HKUST (95.02 μmol g-1). In situ XPS and DFT studies reveal that Cu mainly existed in the form of Cu2O and Cu-MOF, while a unique Cux+ (1 Collapse

Key Words

• CO2 reduction
• Metal–organic framework
• Photocatalysis
• Polyoxometalate

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MESH Headings Collapse

Grants

• 92161103 National Natural Science Foundation of China
• 22071180 National Natural Science Foundation of China
• 22171073 National Natural Science Foundation of China
• 92461314 National Natural Science Foundation of China

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Affiliation(s)

Yu-Jie Wang Institute for New Energy Materials and Low Carbon Technologies, School of Materials Science & Engineering, Tianjin University of Technology, Tianjin, 300384, China Key Laboratory of Polyoxometalate Science of the Ministry of Education, College of Chemistry, Northeast Normal University, Jilin, 130024, China
Xin Cheng Institute for New Energy Materials and Low Carbon Technologies, School of Materials Science & Engineering, Tianjin University of Technology, Tianjin, 300384, China
Na-Na Ma Henan Key Laboratory of Boron Chemistry and Advanced Energy Materials, School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang, 453007, China
Wei-Yi Cheng Henan Key Laboratory of Boron Chemistry and Advanced Energy Materials, School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang, 453007, China
Peng Zhang Institute for New Energy Materials and Low Carbon Technologies, School of Materials Science & Engineering, Tianjin University of Technology, Tianjin, 300384, China
Fang Luo Key Laboratory of Polyoxometalate Science of the Ministry of Education, College of Chemistry, Northeast Normal University, Jilin, 130024, China
Wen-Xiong Shi Institute for New Energy Materials and Low Carbon Technologies, School of Materials Science & Engineering, Tianjin University of Technology, Tianjin, 300384, China
Shuang Yao Institute for New Energy Materials and Low Carbon Technologies, School of Materials Science & Engineering, Tianjin University of Technology, Tianjin, 300384, China
Tong-Bu Lu Institute for New Energy Materials and Low Carbon Technologies, School of Materials Science & Engineering, Tianjin University of Technology, Tianjin, 300384, China
Zhi-Ming Zhang Institute for New Energy Materials and Low Carbon Technologies, School of Materials Science & Engineering, Tianjin University of Technology, Tianjin, 300384, China

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An Aziridine and a 2-Pyrrolidone with Pyridyl Sidearms as Ligands for Cationic Rh(I)-Catalyzed Hydrosilylation and Hydrogenation of C=C and C≡C Bonds

Phosphine- or carbene-based soft ligands are customarily used in Rh and other late transition metal catalyzed alkene and alkyne hydrosilylation and hydrogenation. We report here an aziridine and a 2-pyrrolidone with pyridyl sidearms, whose cationic Rh(I) complexes prove as excellent catalysts for hydrosilylating terminal olefins by Et3SiH giving anti-Markovnikov products selectively. To the best of our knowledge, the [(2-pyrrolidone)-Rh]+ seems to be the most active Rh catalyst recording a highest TOF of 24000 h-1. It works remarkably (TOF: 714 h-1) even at 10 ppm concentration! Terminal alkynes are hydrosilylated too to give β-(Z)-vinylsilanes selectively. Both catalysts also hydrogenate alkenes and doubly-hydrogenate alkynes, both terminal and internal, under ambient and benchtop conditions. But in hydrogenation, the [(aziridine)-Rh]+ catalyst works better. Both ligands and the Rh catalysts are air-stable.

Aminobenzoic Acid Covalently Modified Polyoxotungstates Based on {XW6} Clusters with Proton Conductivity Property

Three cases of aminobenzoic acid hybrid polyoxotungstates, Na3(H3O)2[(HPW6O21) (O2CC6H4NH2)3]·7H2O (1), K2(H3O)4[(AsW6O21)(O2CC6H4NH2)3]·4H2O (2), and [(H2N(CH3)2]3Na2(H3O)[(SbW6O21) (O2CC6H4NH2)3]·7H2O (3), were successfully synthesized. This is the first report of the successful assembly of the hexanuclear {XW6} (X = HPIII, AsIII, or SbIII) clusters and organic carboxylic acid (para aminobenzoic acid) ligands. All three hybrids feature a common {XW6} unit composed of a six-membered {WO6} octahedral ring capped by one {XO3} trigonal pyramid. Furthermore, these hybrids possess an extensive three-dimensional network of hydrogen bonds, which not only provide high thermal stability but also contribute to excellent proton conductive performances. Simultaneously, based on the Hirshfeld partition analysis, combined with the interaction between POMs and water molecules, the proton transport mechanisms of three hybrids were highlighted.

Pyrazine Dicarboxylic Acid and Phosphite-Bridging Lanthanide-Incorporated Tellurotungstates and Their Fluorescence Performances

Two pyrazine dicarboxylic acid and phosphite-bridging lanthanide-incorporated tellurotungstates [H2N(CH3)2]12 Na4[Ln4(H2O)2(H2PDBA)2(HPO3)2W6O10][B-α-TeW8O31]4 · 70H2O [Ln = Eu3+ (1), Tb3+ (2); H2PDBA = 2,5-pyrazine dicarboxylic acid) were prepared, which contain four [B-α-TeW8O31]10- subunits and a deca-nuclear heterometallic [Ln(H2O)2(HPO3)2 (H2PDBA)2(W3O5)2]24+ cluster. Strikingly, two H2PDBA ligands connect two equivalent {W3Eu2O5(H2O)(B-α-TeW8O31)2(HPIIIO3)}8- moieties to form the polyanion skeleton, while the phosphite plays a bridging role in joining two lanthanide centers in the {W3Eu2O5(H2O)(B-α-TeW8O31)2(HPIIIO3)}8- moiety. In addition to the fluorescence (FL) properties of 1 and 2 at room temperature, their temperature-dependent FL properties were also investigated. In 80-298 K, FL intensities of 1 and 2 decrease as temperature increases, and their maximum relative sensitivities (Sr) are 3.70 and 1.99% K-1, whereas the minimum temperature uncertainties (δT) are 1.25 and 1.18 K for 1 and 2. In 298-973 K, upon increasing temperature, FL intensities of 1 and 2 initially rise to their maxima at 373 K and subsequently decrease. This is because samples of 1 and 2 undergo dehydration together with amorphization below 473 K and decomposition above this temperature. This work lays a foundation for the development for luminescent thermometers based on lanthanide-incorporated polyoxometalates.

Stimuli-responsive Zn(ii) complexes showing the structural conversion and on/off switching of catalytic properties

In this work, we report a series of dinuclear Zn(ii) complexes and their corresponding catalytic properties for a transesterification reaction. We show that the structures and catalytic activity of the complexes are strongly dependent on their molecular structures surrounding the metal centres. The use of halides yields a series of [Zn2X4L] (X = Cl, Br, and I) complexes with low catalytic activity because of the fully saturated coordination environment, whereas Zn(ClO4)2 results in two isomeric [ZnL] n 1D coordination polymers with efficient catalytic properties, despite being susceptible to structural rearrangement and consequent changes in catalytic activity over time. The response to chemical stimuli to trigger anion exchange allows for switching on/off the systems' catalytic activity, simultaneously recovering the catalytic effect upon degradation and thus reconstructing the coordination environment of the 1D polymer.

Catalytic Reduction of Aromatic Nitro Compounds to Phenylhydroxylamine and Its Derivatives

Phenylhydroxylamine and its derivates (PHAs) are important chemical intermediates. Phenylhydroxylamines are mainly produced via the catalytic reduction of aromatic nitro compounds. However, this catalytic reduction method prefers to generate thermodynamically stable aromatic amine. Thus, designing suitable catalytic systems, especially catalysts to selectively convert aromatic nitro compounds to PHAs, has received increasing attention but remains challenging. In this review, we initially provide a brief overview of the various strategies employed for the synthesis of PHAs, focusing on reducing aromatic nitro compounds. Subsequently, an in-depth analysis is presented on the catalytic reduction process, encompassing discussions on catalysts, reductants, hydrogen sources, and a comprehensive assessment of the merits and drawbacks of various catalytic systems. Furthermore, a concise overview is provided regarding the progress made in comprehending the mechanisms involved in this process of catalytic reduction of aromatic nitro compounds. Finally, the main challenges and prospects in PHAs' production via catalytic reduction are outlined.

Unraveling the Intertwining Factors Underlying the Assembly of High-Nuclearity Heterometallic Clusters

Two closely related yet distinctly different cationic clusters, [Dy52Ni44(HEIDA)36(OH)138(OAc)24(H2O)30]10+ (1) and [Dy112Ni76(HEIDA)44(EIDA)24(IDA)4(OH)268(OAc)48(H2O)44]4+ (2) (HEIDA=N-(2-hydroxyethyl)iminodiacetate), each featuring a multi-shell core of Platonic and Archimedean polyhedra, were obtained. Depending on the specific conditions used for the co-hydrolysis of Dy3+ and Ni2+, the product can be crystallized out as one particular type of cluster or as a mixture of 1 and 2. How the reaction process was affected by the amount of hydrolysis-facilitating base and/or by the reaction temperature and duration was investigated. It has been found that a reaction at a high temperature and/or for an extended period favors the formation of the compact and thermodynamically more stable 1, while a brief reaction with a large amount of the base is good for the kinetic product 2. By tuning these intertwining conditions, the reaction can be regulated toward a particular product.

A Rare Inorganic-Organic Hybrid Polyoxoboroniobate Based on Pagoda-Shaped {LiB2Nb29O86} Clusters and {Cd2(cis-en)2(trans-en)} Complexes

A new inorganic-organic hybrid polyoxoboroniobate {H4K2[Cu(cis-en)2(H2O)]9[Cu(cis-en)2]6[Cd2(cis-en)2(trans-en)][LiB2Nb29O86]2·79H2O} (1, en = ethylenediamine), is built from pagoda-shaped {LiB2Nb29O86} clusters, linear {Cd2(cis-en)2(trans-en)} bridging units, and copper-amine complexes. The {LiB2Nb29O86} cluster represents the first example of combining oxoboron clusters with polyoxoniobate clusters (PONbs). It consists of an unusual HPONb fragment {LiNb18O54}, a fused-ring structural boroniobate cluster {B2Nb5O13}, and a classical Lindqvist {Nb6O19} fragment. The {Cd2(cis-en)2(trans-en)} and [Cu(cis-en)2]2+ complexes link the pagoda-shaped {LiB2Nb29O86} clusters into 1D infinite ladder chains. This is the first instance of simultaneous coordination of the cis-en and trans-en ligands with a single metal cation in the inorganic-organic hybrid PONb family. Furthermore, 1 exhibits good proton conductivity.

Single Dispersion of Fe(H2O)2-Based Polyoxometalate on Polymeric Carbon Nitride for Biomimetic CH4 Photooxidation

Direct methane conversion to value-added oxygenates under mild conditions with in-depth mechanism investigation has attracted wide interest. Inspired by methane monooxygenase, the K9Na2Fe(H2O)2{[γ-SiW9O34Fe(H2O)]}2·25H2O polyoxometalate (Fe-POM) with well-defined Fe(H2O)2 sites is synthesized to clarify the key role of Fe species and their microenvironment toward CH4 photooxidation. The Fe-POM can efficiently drive the conversion of CH4 to HCOOH with a yield of 1570.0 µmol gPOM -1 and 95.8% selectivity at ambient conditions, much superior to that of [Fe(H2O)SiW11O39]5- with Fe(H2O) active site, [Fe2SiW10O38(OH)]2 14- and [P8W48O184Fe16(OH)28(H2O)4]20- with multinuclear Fe-OH-Fe active sites. Single-dispersion of Fe-POM on polymeric carbon nitride (PCN) is facilely achieved to provide single-cluster functionalized PCN with well-defined Fe(H2O)2 site, the HCOOH yield can be improved to 5981.3 µmol gPOM -1. Systemic investigations demonstrate that the (WO)4-Fe(H2O)2 can supply Fe═O active center for C-H activation via forming (WO)4-Fea-Ot···CH4 intermediate, similar to that for CH4 oxidation in the monooxygenase. This work highlights a promising and facile strategy for single dispersion of ≈1-2 Å metal center with precise coordination microenvironment by uniformly anchoring nanoscale molecular clusters, which provides a well-defined model for in-depth mechanism research.

The effect of ionic versus covalent functionalization of polyoxometalate hybrid materials with coordinating subunits on their stability and interaction with DNA

Inorganic-organic hybrid materials that combine both Polyoxometalates (POMs) and metal ion coordinating subunits (CSUs) represent promising multifunctional materials. Though their individual components are often biologically active, utilization of hybrid materials in bioassays significantly depends on the functionalization method and thus resulting stability of the system. Quite intriguingly, these aspects were very scarcely studied in hybrid materials based on the Wells-Dawson POM (WD POM) scaffold and remain unknown. We chose two model WD POM hybrid systems to establish how the functionalization mode (ionic vs. covalent) affects their stability in biological medium and interaction with nucleic acids. The synthetic scope and limitations of the covalent POM-terpyridine hybrids were demonstrated and compared with the ionic Complex-Decorated Surfactant Encapsulated-Clusters (CD-SECs) hybrids. The nature of POM and CSU binding can be utilized to modulate the stability of the hybrid and the extent of DNA binding. The above systems show potential to behave as model cargo-platforms for potential utilization in medicine and pharmacy.

Three Polyoxometalate-Based Ag-Organic Compounds as Heterogeneous Catalysts for the Synthesis of Benzimidazoles

Three new POM-based compounds, with formulae [Na0.63Ag3(Htba)2.37(tba)0.63(H2O)2(PMo12O40)]·4H2O (Ag3PMo), [Ag4(Htba)4(H2O)2(PMo12O40)](NO3)·H2O (Ag4PMo), and [Ag3(Htba)2(tba)(PW12O40)0.5](NO3)0.5·13H2O (Ag3PW), were prepared with a 3-(4H-1,2,4-triazol-4-yl)benzoic acid (Htba) ligand, Keggin-type anions ([PMo12O40]3-/[PW12O40]3-), and a silver ion (Ag+). The structural features of these compounds are particularly different from the multinuclear subunits, which are [Ag3(tba)3] clusters in Ag3PMo, [Ag4(tba)3] chains in Ag4PMo, and [Ag3(tba)3]2 clusters in Ag3PW, connected by multidonor atom tba ligands and Ag+ ions. Meanwhile, in these compounds, polyanions act as polydentate ligands to link adjacent Ag-tba metal-organic units and expand their spatial dimensions. These compounds, as heterogeneous catalysts, exhibit high stability and excellent catalytic activity to construct benzimidazoles. Ag3PMo could efficiently catalyze the condensation of benzene-1,2-diamines and benzaldehydes and produce benzimidazoles in good yields. In addition, Ag3PMo could be reused up to 7 times and was suitable for gram-scale reactions.