Abstract The [3 + 3]‐cyclization reaction of N‐hydroxyphthalimide acrylates with N‐tosyl ketimines proceeds in moderate to high yields and with excellent enantiomeric excess.
Purely inorganic porous frameworks using catalytically active [MnV13O38]7− clusters as nodes and rare earth ions as linkers have been successfully prepared. The POM-based porous framework is a kind of multifunctional material, which exhibits selective adsorption behavior and remarkable catalytic activity for the heterogeneous oxidation of sulfides.
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< x ≤2) surface layer formed upon the Cu2O matrix surrounding POMs for CO2 absorption and activation. Systematic investigations demonstrate that the electron‐sponge can efficiently capture electrons from excited Cu2O to promote the generation of a Cux+ surface layer, while the closely surface‐coating metal‐organic layer can act as protective layer and CO2 adsorbent. This dual function concurrently contributes to promote photocatalysis and prevent Cu2O degradation. Remarkably, the ternary composites exhibit much enhanced photochemical stability and can be used for over 60 h without noticeable activity loss.
Two nanosized hexameric polyoxometalate-based solid state assemblies (H2en)6Na15K9[Dy6Fe6(H2O)12(SiW10O38)6]·34H2O (1) and K13Na17[H2en]3[Tb6Fe6(H2O)12(SiW10O38)6]·40H2O (2) (en = 1,2-ethylenediamine), decorated by six [Ln-(μ3-O)3-Fe] 3d–4f heterometallic clusters, have been synthesized by the hydrothermal method, and characterized by IR, element analysis, magnetic studies and the single-crystal X-ray analyses. The detailed study of the synthetic conditions reveals that the use of the organic ligands, pH value and the reaction temperature all play important roles in the synthesis of the 3d–4f heterometallic POMs. Magnetic study suggests the presence of antiferromagnetic interactions in these two compounds.
Certain agricultural management practices are known to affect the soil microbial community structure; however, knowledge of the response of the fungal community structure to the long-term continuous cropping and rotation of soybean, maize and wheat in the same agroecosystem is limited. We assessed the fungal abundance, composition and diversity among soybean rotation, maize rotation and wheat rotation systems and among long-term continuous cropping systems of soybean, maize and wheat as the effect of crop types on fungal community structure. We compared these fungal parameters of same crop between long-term crop rotation and continuous cropping systems as the effect of cropping systems on fungal community structure. The fungal abundance and composition were measured by quantitative real-time PCR and Illumina MiSeq sequencing. The results revealed that long-term continuous soybean cropping increased the soil fungal abundance compared with soybean rotation, and the fungal abundance was decreased in long-term continuous maize cropping compared with maize rotation. The long-term continuous soybean cropping also exhibited increased soil fungal diversity. The variation in the fungal community structure among the three crops was greater than that between long-term continuous cropping and rotation cropping. Mortierella, Guehomyces and Alternaria were the most important contributors to the dissimilarity of the fungal communities between the continuous cropping and rotation cropping of soybean, maize and wheat. There were 11 potential pathogen and 11 potential biocontrol fungi identified, and the relative abundance of most of the potential pathogenic fungi increased during the long-term continuous cropping of all three crops. The relative abundance of most biocontrol fungi increased in long-term continuous soybean cropping but decreased in long-term continuous maize and wheat cropping. Our results indicate that the response of the soil fungal community structure to long-term continuous cropping varies based upon crop types.
The electronic structures of [ CpTi · SiW 9 V 3 O 40 ] 4- constructed from Keggin–type polyoxometalates functionalized by CpTi 3+ group have been investigated by Density Functional Theory (DFT) methods. We discuss the relative stability affected by incorporating the CpTi 3+ group into the different sites of the [ SiW 9 V 3 O 40 ] 7- framework on the basis of geometrical parameters, total bonding energies, fragment analysis and frontier molecular orbitals analysis. The calculated results indicated that the structure of the CpTi 3+ group coordinating to one terminal oxygen and two bridging oxygen atoms of the Keggin–type polyoxoanion (system a) is more stable than that to three bridging oxygen atoms (system b). In system a, Ti -Ob1, Ti -Ob2 and Ti - Ot1 are relatively shorter, and as result, it exhibits a more compact and nearly spherical structure of the well-known Keggin–type [ SiW 9 V 3 O 40 ] 7- . Fragment analysis elucidates that there is deviation of ΔE B in systems a and b, which makes a significant contribution to the stability of system a. The stability of different isomeric forms of polyoxoanions appears to be a balance between the stabilizing ΔE O and ΔE E terms and the destabilizing ΔE P term. The relatively small energy differences (ΔE B = 4.26 eV ) between systems a and b arise directly from this balance. Frontier molecular orbitals analysis further confirms the stability order of systems a > b by the difference of the HOMO-LUMO energy gap.
The reaction between K12[H2P2W12O48] and CuCl2 in a NaCl aqueous solution assisted with organoamines (1,2-ethylenediamine (en), 1,6-hexamethylene diamine (hn), or both) leads to the isolation of three compounds: K4Na10[α1-CuP2W17O60(OH)]2·∼58H2O (1), Na2[H2en][H2hn]0.5[Cu(en)2]4.5[α1-CuP2W17O60(OH)]2·∼43H2O (2), and Na3[H2hn]2.5[α1-P2W17O60Cu(OH)2]·∼14H2O (3). The polyoxoanion [α1-CuP2W17O60(OH)]214− in 1 and 2 exhibits a double-Dawson-type polyoxoanion that consists of two α1-type mono-Cu-substituted Wells—Dawson anions, which can be synthesized by both the conventional aqueous solution method and the hydrothermal technique. Furthermore, the double-Dawson-type polyoxoanions in 2 are linked by the [Cu(en)2]2+ bridges to form 2-D networks, which are further packed into a 3-D supramolecular porous framework via extensive hydrogen bonding interactions, exhibiting two types of tunnels (A and B). Compound 3 possesses a 3-D supramolecular framework with 1-D tunnels constructed from the α1-type mono-Cu-substituted Wells—Dawson anion. The magnetic studies of compounds 1 and 2 indicate that weak antiferromagnetic interactions exist in these two compounds.
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