Search

Three imidazole-modified Ag-polyoxovanadates frameworks (APFs) with a controllable molar ratio of Ag+ to polyoxovanadates (POVs) [Ag(IM)2]2V4O12∙2Ag(IM)2 (APF-1), [Ag2(1-eIM)4]2[Ag(1-eIM)2]3∙2Ag(1-eIM)2∙3(1-HeIM)[V10O28]2 (APF-2) and [Ag(1-pIM)2]3[HV10O28]∙2Ag(1-pIM)2∙2H2O (APF-3) (IM = imidazole; 1-eIM = 1-ethylimidazole and 1-pIM = 1-propylimidazole) have been successfully achieved by self-assembly of POVs, Ag+ cations, and three different imidazole derivatives. Interestingly, the molar ratios of Ag+ to POVs vary from 4:1, 4.5:1 to 5:1 by changing the vanadium resources and imidazole derivatives. Notably, the coordination environment of Ag+ cations and the structure of POVs in the APFs are also different. Specifically, for APF-1, the four Ag atoms adopt three-coordinated and four-coordinated geometries, respectively, and Ag-imidazole complexes and [V4O12]4− cluster form the one-dimensional polymeric chains. While Ag atoms in APF-2 and APF-3 exhibit two-, four- and five-coordinated geometries for APF-2, four-, five- and six-coordinated geometries for APF-3, respectively. These Ag+ cations and decavanadate clusters are assembled into the 2D supramolecular structure through the Ag-O bonds and Ag…Ag argentophilic interaction. Remarkably, thus-obtained APF-2 can serve as powerful efficient heterogeneous catalyst for construction of C-N bond and detoxification of simulant sulfur mustard (yields up to 99%), which enable successful recycling for three cycles with remained catalytic activities and structure stability.

A family of microporous and acid–base Ln-MOFs (1-Ln, Ln = Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb) has been synthesized from the H3NTB ligand. 1-Ln can efficiently catalyze both cycloaddition of epoxides with CO2 and one-pot cascade deacetalization–Knoevenagel reactions.

The selective oxidation of amines into imines is a priority research topic in organic synthesis and has attracted much attention over the past few decades. However, the oxidation of amines generally suffers from the drawback of transition-metal, even noble-metal catalysts. Thus, the strategy of metal- and oxidant-free selective synthesis of imines is highly desirable yet largely unmet. This paper unravels a metal-free and external oxidant-free electrochemical strategy for the oxidative coupling methodology of amines. This general transformation is compatible with various functional amines and led to functionalized imines in moderate to satisfactory yields.

A condition-controlled strategy for selectively synthesis of 2-acylbenzothiazoles and bibenzo[b][1,4]thiazines from aryl methyl ketones and disulfanediyldianilines was realized using I2/DMSO or I2/MeCN systems, respectively. The desired products were synthesized in only 15 min with moderate to excellent yields (50%-90%) under microwave-assisted, metal-free conditions. The strategy provides a great advantage for selective synthetic applications in the efficient synthesis of benzothiazoles and bibenzothiazines heterocycle compounds.

Four transition-metal lacunary polyoxometalates (TM-LPOMs, TM = Cu, Co, Ni, and Mn) are prepared and fabricated into ultralow density LPOM-based foams (LPOMs@CMC) for the efficient flowing catalytic production of sulfenamide additives.

Guided by a second-sphere interaction strategy, we fabricated a Tb(III)-based metal-organic framework (MMCF-4) for turn-on sensing of methyl amine with ultra-low detection limit and high turn-on efficiency. MMCF-4 features lanthanide nodes shielded in a nonacoordinate geometry along with secondary coordination spheres that are densely populated with H-bond interacting sites. Nonradiative routes were inhibited by binding-induced rigidification of the ligand on the second coordination sphere, resulting in luminescence amplification. Such remote interacting mechanism involved in the turn-on sensing event was confirmed by single-crystal X-ray diffraction and molecular dynamic simulation studies. The design of both primary and secondary coordination spheres of Tb(III) enabled the first turn-on sensing of organic amines in aqueous conditions. Our work suggests a promising strategy for high-performance turn-on sensing for Ln-MOFs and luminous materials driven by other metal chromophores.

Summary γ-butyrolactone (γ-BL), serving as the monomer of biocompatible and recyclable poly(γ-butyrolactone) plastic, faces a giant challenge in ring-opening polymerization (ROP) due to its low strain energy. The ROP of γ-BL is generally achieved under harsh conditions (e.g., high-pressure or gas-protected atmosphere) and is mostly based on homogeneous systems. Here, we synthesize a series of lanthanum metal-organic framework-based porous nanospheres and successfully apply them as heterogeneous catalysts in efficient ROP of γ-BL under mild conditions. Specifically, NNU-mIM-3 presents a yield of 24.6% with low polydispersity distribution centered at 3.6 kDa and the obtained PγBL can be completely and quantitatively recycled into monomers by simple heat treatment. Besides, the ROP catalysis systems have been intensively explored with various imine-based additives, proven to exhibit largely improved performance with PγBL yield of ~50% and Mw of ~8 kDa. This work paves a new way to explore novel heterogeneous catalysts in producing biocompatible and degradable plastics.

An addition of H-phosphonates to aryl alkynes was realized under solvent- and metal-free conditions, affording Markovnikov-selective α-vinylphosphonates in moderate to good yields. A wide range of aryl alkynes could be applied for the reaction. A tentative mechanism of addition–substitution was proposed based on in situ 31P {1H} NMR studies.

Polyoxometalates (POMs) is a kind of metal-oxygen clusters with well-defined structures, controllable composition, and excellent properties including acidity, redox properties, etc . In recent years, POMs have shown potential application in the field of catalysis, materials, energy conversion and pharmaceuticals and become a hot interdisciplinary research area. This review focuses on the recent progress in the structure design of POMs and their catalytic properties, mainly including POM structure chemistry, acid-base catalysis, redox catalysis, photocatalysis, the catalytic conversion of CO2 and toxic molecules. In addition, the future development of POMs-based catalysis is prospected.

Ti3C2 belongs to MXenes family, which is a new two-dimensional material and has been applied in many fields. With simple method of hydrothermal and high temperature calcination, nanostructured Ni/Ti3C2Tx hybrid was synthesized. The stable layer structure of Ti3C2 MXene providing high surface area as well as excellent electronic conductivity are beneficial for deposition and decomposition of discharge product Li2O2. Furthermore, possessing special catalytic activity, Ni nanoparticles with size of about 20 nm could accelerate Li2O2 breaking down. Taking advantage of two kinds of materials, Ni/Ti3C2Tx hybrid as cathode of Li-O2 battery can achieve a maximal specific capacity of 20,264 mAh/g in 100 mA/g and 10,699 mAh/g in 500 mA/g at the first cycle. This work confirms that the prepared Ni/Ti3C2Tx hybrid exhibiting better cycling stability points out a new guideline to improve the electrochemical performance of lithium-oxygen batteries.

We reported an economic and practical ball-milling method for the synthesis of tetrahydroquinoline derivatives via a ‘one-pot’ three-component Diels-Alder reaction of anilines, aldehydes and alkenes catalyzed by phosphotungstic acid at room temperature. For this reaction, a simple “one-pot” ball-milling operation was conducted, readily available starting materials were employed, ‘one-pot’ conditions were applied, and the most important was to use inexpensive and environmentally friendly catalyst phosphotungstic acid. Various tetrahydroquinolines, which might be potentially applicable in the pharmaceutical and biochemical areas, were conveniently synthesized in moderate to excellent yields.

Polyester plastics such as poly(ethylene terephthalate) (PET) are utilized commonly in everyday life, yet only a small portion of these plastics are recycled, and typically, the recycling procedure...

The synthesis of two sulfur-decorated perylene diimides, the five-membered S-heterocyclic annulated perylene diimide (1) and 1-propanethiol- N,N′-dicyclohexylperylene-3,4,9,10-tetracarboxylic diimide (2), and a novel sulfoxide-containing perylene diimide, 1-propyl sulfoxide- N,N′-dicyclohexylperylene-3,4,9,10-tetracarboxylic diimide (3), are reported. The photophysical, electrochemical, aggregation, and thermal properties of these compounds are investigated by ultraviolet visible absorption, fluorescence, cyclic voltammetric, X-ray diffraction, and thermogravimetric analysis techniques. The geometries of the compounds are optimized at the 6-31G* level of theory using density functional theory, and their potentials are correlated with molecular orbitals. The prepared perylene diimide derivatives exhibit narrow the highest occupied molecular orbitals and the lowest unoccupied molecular orbitals band gaps, and they have quite different absorptions and emissions in dichloromethane solutions, which are in agreement with the density functional theory–calculated results.

A sulfur-decorated perylene derivative, 1-propanethiol-N,N′-dicyclohexyl perylene-3,4,9,10 tetracarboxylic diimide (PTPDI), was synthesized and fully characterized by 1H NMR, 13C NMR, FTIR, HRMS, UV–vis absorption, fluorescence, fluorescence lifetime, fluorescence quantum yield, cyclic voltammetry, and thermogravimetric techniques. The optical, fluorescence, and scanning electron microscopies were employed to study its self-assembly process. The photophysical properties were affected strongly by modifying the propanethiol unit linking to the perylene core. Furthermore, the chromophore showed two irreversible oxidations and two quasi-reversible reductions in dichloromethane at modest potential. The optical properties of PTPDI in various conditions and complementary density functional theory calculations were reported. Due to steric hindrance of the bulky n-propyl mercaptan substituent, PTPDI molecules are arranged in slipped face-to-face fashion to form J-aggregates. Thus, the intermolecular π–π actions of the molecule are weak, causing its high luminescence efficiency. In the meantime, the space between perylene cores is very short (3.45 Å), which is favorable for the hopping transportation of charge carrier from one molecule to an adjacent one. PTPDI could be a candidate material for acquiring a well-defined organic nanostructure with excellent charge-transporting and light-emitting capabilities.

A highly efficient and reusable catalyst QA-HPMV was successfully prepared by the reaction of quinoline-2-formic acid (QA) with molybdovanadophosphoric heteropolyacid (H4PMo11VO40, HPMV) for the nitration of benzene. The physical and chemical properties of the sample was characterized by X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), UV-Vis and thermogravimetric analysis (TG). The characterization results showed that the formed QA-HPMV retained the Keggin structure of HPMV. As a catalyst for benzene nitration, QA-HPMV showed good catalytic performance and the yield of nitrobenzene was 82.5% under the optimized reaction conditions. As a heterogeneous catalyst, QA-HPMV can be easily recycled from the reaction medium by filtering and remained highly catalytic performance even after five runs of recycling.

Two novel organic–inorganic hybrid polyoxovanadates, i.e., [Ni(1-mIM)4(H2O)2][Ni(H2O)5]2V10O28·5.5H2O (compound 1) and [V(O)(1-vIM)4]2V4O12·H2O (compound 2) (1-mIM = 1-methylimidazole; 1-vIM = 1-vinylimidazole) were synthesized under routine conditions. The two polyoxovanadate hybrids were further unequivocally characterized by the usual physicochemical techniques such as single crystal X-ray diffraction (SCXRD), Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction (PXRD), thermogravimetric (TG) analyses and elemental analyses. The SCXRD analyses demonstrated that the three Ni2+ atoms of compound 1 presented distorted octahedral geometry; one of the three Ni2+ atoms coordinated with four 1-mIM molecules and two coordinated water molecules, thereby exhibiting a [NiN4O2] binding set. Furthermore, the other two Ni2+ atoms were coordinated with five water molecules and one decavanadate polyanion, presenting an [NiO6] coordination environment. The structure of 2 exhibited a central [V4O12]4− unit attached to the opposite sides of two [V(O)(1-vIM)4]2 groups, in which the V center displayed distorted octahedral configuration. More importantly, the two organic–inorganic hybrid polyoxovanadates were further studied using the Knoevenagel condensation reaction, and they were found to display efficient heterogeneous catalytic activities (yield up to 99%). The catalytic performance of compound 1 did not decrease even after three runs of catalytic cycling.

By virtue of their structural periodicity, tunability, high porosity and rich functionality, metal–organic frameworks (MOFs) are of great interest in catalysis. However, MOF crystals are fragile and difficult to use as robust adsorbents or catalysts without processing into shapes. Precise control of particle size and catalytic sites for MOFs during the shaping procedures is also highly desired yet hard to realize. A versatile size control method for lanthanide MOFs, especially our newly designed Ce-MOF (BIT-58), is developed. The coordination and steric effects of various modulators are investigated. With size reduction from micrometers to nanometers (∼25 μm to ∼30 nm), more accessible metal sites of BIT-58 are exposed (10 times increased acid site amount; 7 times higher mesopore volume) and the catalytic performance is significantly improved. Furthermore, nano-sized BIT-58 can be processed into films or coatings with excellent catalytic activity, which holds great potential in batch or continuous-flow catalytic processes.

Two Schiff base copper(II) complexes, [Cu(R-L) (CH3OH)]8 (1) and [Cu(S-L) (CH3OH)]4 (2) {[R/S-H2L = R/S-3-phenyl-2-(2-hydroxy-5-chlorobenzylideneamino)propane-1-ol]}, have been successfully achieved and fully characterized by single-crystal X-ray diffraction (SXRD), mass spectrometry (MS), Fourier transform infrared spectroscopy (FT-IR), and elemental analysis (EA). The interactions of complexes 1 and 2 with calf thymus DNA (CT-DNA) and bovine serum albumin (BSA) have been comprehensively investigated using various electronic absorption spectroscopies. The thermal denaturation, viscosity, and UV-Vis spectra data suggested non-intercalative binding between DNA and the complexes. Additionally, an in vitro cytotoxicity test on the two complexes towards four types of human cancerous cell lines (HL-60, Caco-2, A549, and HeLa) indicated that the two complexes exhibited substantial cytotoxic activity. Especially, complex 2 exhibited excellent data, with IC50 = 10.97 ± 1.22 against HL-60 cells, which indicated that the two chiral complexes play significant roles in the cytotoxicity and interactions with DNA and BSA.

Reaction of two related rigid terpyridine ligands, 4′-(4-cyanophenyl)-4,2′:6′,4-terpyridine (L1) and its derivative, 4′-(4-carboxyphenyl)-4,2′:6′,4-terpyridine (L2), with transition metal ions (Co2+ or Cu2+/Cu+), afforded four novel coordination compounds: Co(L1)Cl2 (1), Co3(L1)3Cl6 (2), CuI9(L1)4.5(CN)9 (3), and [CuII3(L2)6(H2O)6]·4H2O (4). Crystal structure analysis reveals that 1 is comprised of single-stranded 21 helical chains, and weak interactions involving C–H···Cl weak hydrogen bonding and π–π stacking interactions exist in the structure. The structure of 2 is comprised of 32 helices, which is compared with the structure of compound 1. 3 shows a three-dimensional (3D) 4-fold interpenetration structure. 4 exhibits a one-dimensional gridlike belt structure, which further builds 3D supramolecular architecture via π–π stacking interactions. These novel coordination compounds show exceptional catalytic activity for the oxidation of benzylic C–H bonds. Notably, compound 4 shows the best catalytic prope...

Three novel inorganic–organic hybrid copper vanadates α-[Cu(mIM)4]V2O6 (1), β-[Cu(mIM)4]V2O6 (2), and [Cu(mIM)2)](VO3)2 (3) (mIM = 1-methylimidazole) have been synthesized by rationally controlling of the hydrothermal conditions and fully characterized by single-crystal XRD, powder XRD, elemental analyses, TGA, and FT-IR spectroscopy. Interestingly, compounds 1 and 2 were isolated as geometric isomers by tuning the solvothermal reaction temperature. Because of the different coordination modes between the tetradentate [V4O12]4– and [Cu(mIM)4]2+ subunits, the supramolecular structures of the two isomers show a 3D framework with an interpenetrating diamond topology for 1 and a 2D network for 2, respectively. Compound 3 was obtained by tuning the reaction temperature and the ratio of mIM/H2O, which showed interesting left- and right-handed helixes with an identical pitch of ca. 5.388 A in its 2D network structure. As heterogeneous catalysts, compounds 1–3 exhibit excellent catalytic performance in the oxidati...

Binary Pd-polyoxometalates (Pd(dpa)2)3- (PW12O40)2·12 DMSO (2), (Pd(dpa)2)3(PMo12O40)2·12 DMSO· 2H 2O (3), and (Pd(dpa)(DMSO)2)2(HPMo10V2O40)·4 DMSO (4) were synthesized by reaction of (Pd(dpa)(OAc)2)· 2H 2 O( 1; dpa = 2,2'-dipyridylamine) with three Keggin-type polyoxometa- lates and fully characterized by single-crystal and powder XRD analyses, IR spectroscopy, and elemental analyses. The synthesis is facile and straightforward, and the complicated ligand-modification procedure often used in the traditional charge-transfer method can be omitted. In 2-4, Pd com- plexes and polyoxometalate anions are coupled through electrostatic interaction. Compound 4 is more active than the other three compounds in the selective aerobic oxida- tion of alcohols at ambient pressure. Interestingly, dur- ing catalytic recycling of compound 4, unprecedented ternary Pd-V-polyoxometalate (Pd(dpa)2{VO(DMSO)5}2)- (PMo12O40)2·4 DMSO (5), which was captured and character- ized by single-crystal XRD, proved to be the true active spe- cies and showed high catalytic activity for the selective aero- bic oxidation of aromatic alcohols (98.1-99.8 % conversion, 91.5-99.1 % selectivity). Moreover, on the basis of control ex- periments and EPR and UV/Vis spectra, a plausible reaction mechanism for the oxidation of alcohols catalyzed by 5 was proposed.

HKUST-1@Fe3O4 chemically bonded core-shell nanoparticles have been prepared by growing HKUST-1 thin layers joined by carboxyl groups onto Fe3O4 nanospheres. These magnetic core-shell MOF nanostructures show exceptional catalytic activity for the oxidation of benzylic C-H bonds and they can be recovered by magnetic separation and reused without losing any activity.

The applications of metal-organic frameworks (MOFs) toward industrial separation, catalysis, sensing, and some sophisticated devices are drastically affected by their intrinsic fragility and poor processability. Unlike organic polymers, MOF crystals are insoluble in any solvents and are usually not thermoplastic, which means traditional solvent- or melting-based processing techniques are not applicable for MOFs. Herein, a continuous phase transformation processing strategy is proposed for fabricating and shaping MOFs into processable fluids, shaped bodies, and even MOF foams that are capable of reversible transformation among these states. Based on this strategy, a cup-shaped Cu-MOF composite and hierarchically porous MOF foam were developed for highly efficient catalytic C-H oxidation (conv. 76% and sele. 93% for cup-shaped Cu-MOF composite and conv. 92% and sele. 97% for porous foam) with ease of recycling and dramatically improved kinetics. Furthermore, various MOF-based foams with low densities (0.1 g cm(-3)) and high MOF loadings (up to 80 wt %) were obtained via this protocol. Imparted with hierarchically porous structures and fully accessible MOFs uniformly distributed, these foams presented low energy penalty (pressure drop20 Pa, at 500 mL min(-1)) and showed potential applications as efficient membrane reactors.

Metal-organic frameworks (MOFs), as a class of microporous materials with well-defined channels and rich functionalities, hold great promise for various applications. Yet the formation and crystallization processes of various MOFs with distinct topology, connectivity, and properties remain largely unclear, and the control of such processes is rather challenging. Starting from a 0D Cu coordination polyhedron, MOP-1, we successfully unfolded it to give a new 1D-MOF by a single-crystal-to-single-crystal (SCSC) transformation process at room temperature as confirmed by SXRD. We also monitored the continuous transformation states by FTIR and PXRD. Cu MOFs with 2D and 3D networks were also obtained from this 1D-MOF by SCSC transformations. Furthermore, Cu MOFs with 0D, 1D, and 3D networks, MOP-1, 1D-MOF, and HKUST-1, show unique performances in the kinetics of the C-H bond catalytic oxidation reaction.

Three zinc-trimesic acid (Zn-BTC) MOFs, BIT-101, BIT-102 and BIT-103, have been synthesized via a structure-directing strategy. Interestingly, BIT-102 and -103 exhibit extraordinary catalytic performance (up to Conv. 100% and Sele. 95.2%) in the cycloaddition of CO2 under solvent- and halogen-free conditions without any additives or co-catalysts.

Cluster cat: Three new imidazole-functionalized neutral hexanuclear vanadium clusters have been prepared, one of which shows exceptional catalytic activity in the selective aerobic oxidation of alcohols (see scheme). Furthermore, these new polyoxovanadium clusters can be readily recycled and reused with unchanged catalytic activity. A plausible catalytic cycle is also proposed.

A new synthetic approach is developed and nine distinct organic functionalized oxomolybdenum complexes, 1–9, are synthesized and fully characterized. Specifically by altering the functional groups on imidazoles we succeeded in making a series of crystalline structures with unique underlying topologies and/or functionalities. These imidazole derivatives can act as ligands, structural directing agents, counter cations and simultaneously, solvents where the reactions and the crystallization occur.

Two new chiral hexanuclear palladium(II) complexes [Pd6(Cys)4(CysH)4][Pd6(CysH)8]Cl4·24H2O (1) and [Pd6(HCys)10](NO3)2·11H2O (2) are prepared through careful control of the reaction conditions. Both complexes comprise two alternately arranged isomerous hexanuclear Pd(II) clusters. As supported by ESI-MS spectra and CD analyses, the integrity of the structures can be maintained in aqueous solution and the chirality of L-Cys ligands can be preserved to the multinuclear Pd complexes.