ABSTRACT
Carbon dioxide (CO2) and the combustion of sulfide in gasoline are the main causes of air pollution. A great deal of attention has been paid to solving the problem and the catalytic reaction seems to be a decent choice. Due to the high-density of Lewis acidic active sites, polyoxometalates are undoubtedly an ideal choice for the sulfur oxidation reaction. With the reasons foregoing, two novel Zn-capped polyoxometalate-based organic-inorganic hybrids, {[α-PMoV2MoVI10O39(OH)Zn2][bbbm]3}·0.5C2H5OH (1) and TBA2{[ε-PMoV8MoVI4O37(OH)3Zn4][phim]3} (2) ((where bbbm = 1-(4-imidazol-1-ylbutyl) imidazole) and phim = 2-phenylimidazole) were successfully obtained by hydrothermal synthesis. In the two compounds, the N-donor ligands in a monodentate or bidentate coordination mode are directly connected to the Keggin anions by Zn-capped atoms, forming an extended one-dimensional chain. It is noteworthy that compound 2 ends up with an interesting spiral infinite chain possibly thanks to the TBA+ cations residing in gaps as structure-directing agents. Simultaneously, the catalytic properties indicate that compounds 1 and2 as efficient heterogeneous catalysts display a decent catalytic activity in the sulfur removal process. Especially, 2 enabled satisfying catalytic oxidation of dibenzothiophene (DBT) to produce more valuable dibenzothiophene sulfone (DBTO2) at 55 °C, and the conversion almost reached 99%. Besides, compound 2 also shows satisfactory catalytic effectiveness in the oxidation of various epoxides in the CO2 cycloaddition reaction, which suggests that compound 2 has the potential to function as a dual functional material with tremendous prospects in sulfur oxidation and carbon dioxide cycloaddition for the first time.
ABSTRACT
Designing and synthesizing lanthanide clusters have always been a research hotspot. Herein, three lanthanide clusters with the formula [Ln8(IN)14(µ3-OH)8(µ2-OH)2(H2O)8]·xH2O (Ln = 1-Gd and x = 11; Ln = 2-Dy and x = 8; Ln = 3-Eu and x = 8) have been isolated in the presence of isonicotinic acid under solvothermal conditions. Structural analysis indicates that those three compounds are isostructural, featuring boat-shaped {Ln8} metal frameworks. Magnetic measurements reveal that 1-Gd exhibits a larger MCE with the maximum -ΔSm value of 31.77 J kg-1 K-1 at 2 K for ΔH = 7 T, while 2-Dy displays slow magnetization relaxation. Besides, the photoluminescence properties of 3-Eu were investigated.
ABSTRACT
Two Ni-substituted polyoxometalates (NiSPs), [Ni6(Py)6(H2O)5(µ3-OH)3(PW9O34)]2·10H2O (1), [Ni7(Py)6(Im)(H2O)5O(WO4)(µ3-OH)3(H2PW9O34)]·3H2O (2) (Py = pyridine, Im = imidazole), were successfully hydrothermally synthesized. Compounds 1 and 2 have significantly different configurations by introducing different amounts of imidazole ligands. For compound 1, two malposed {Ni6(Py)6PW9} units that are face to face are bridged by two Ni-O-W bonds to constitute an isolated dimeric structure. Differently, the {Ni7(Py)6(Im)PW9}2 dimer in compound 2 connects with four adjacent dimers by four {WO4} groups in an interesting two-dimensional (2-D) arrangement. The magnetism of compounds 1 and 2 was studied, and magnetic test results demonstrated that both compounds have ferromagnetic interactions between the nickel centers. Meanwhile, the third-order nonlinear optical (NLO) measurements indicated that compound 1 can serve as potential nonlinear optical materials.
ABSTRACT
Two new bifunctional isolated hybrid compounds, [ε-PMoV8MoVI4O37(OH)3Zn4][iql]4·6H2O (1) and [ε-PMoV8MoVI4O38(OH)2Zn4][bipy]3[(CH3COO)(bipy)2Zn]·2H2O (2) (where iql = isoquinoline and bipy = 2,2'-bipyridine), based on Zn-ε-Keggin were successfully synthesized by self-assembly under hydrothermal conditions. It is interesting to note that acetate in 2 acted as a linker connecting the ε-Keggin anion with the one Zn atom (Zn5) and enabled the ε-Keggin anion to coordinate with more bipy ligands, culminating with a larger isolated system, which is the first reported isolated cluster of Zn5PMo12. Meanwhile, compounds 1-2 show great electrochemical behaviors and excellent electrocatalytic activity for the degradation of NaNO2. In addition, compound 2 displays better third-order NLO performance than 1 due to the presence of more conjugated rings, with a TPA cross section (σ) of 1819 GM, which suggests that compound 2 has the potential to function as a bifunctional material with tremendous prospects.
