Yuan-Biao Huang

Palladium Nanoparticles Encapsulated in a Metal–Organic Framework as Efficient Heterogeneous Catalysts for Direct C2 Arylation of Indoles

Highly dispersed palladium nanoparticles (Pd NPs) encapsulated in the mesoporous cages of the metal-organic framework (MOF) MIL-101(Cr) have been prepared by using the wetness impregnation method. The Pd NPs were characterized by powder X-ray diffraction (PXRD), N(2) adsorption, transmission electron microscopy, inductively coupled plasma atomic emission spectroscopy (ICP-AES), and X-ray photoelectron spectroscopy (XPS). The particles size ((2.6±0.5) nm) of the obtained Pd NPs was in good agreement with the cage diameters (2.9 and 3.4 nm) of the MOF. The resulting Pd/MIL-101(Cr) catalyst exhibited extremely high catalytic activities in the direct C2 arylation of substituted indoles by using only 0.1 mol% of the Pd catalyst. Moreover, the catalyst is easily recoverable and can be reused several times without leaching into solution and loss of activity. The combination of the highly dispersible Pd NPs within the accessible mesoporous cages and the favorable adsorption of the aryl halides on MIL-101 are suspected to be the main reasons for the observed high activities of the Pd/MIL-101(Cr) catalyst in the direct C2 arylation of indoles.

Construction of a Polyhedral Metal–Organic Framework via a Flexible Octacarboxylate Ligand for Gas Adsorption and Separation

A flexible octacarboxylate ligand, tetrakis[(3,5-dicarboxyphenyl)oxamethyl]methane (H8X), has been used to construct a highly porous metal-organic framework (In2X)(Me2NH2)2(DMF)9(H2O)5 (1), which is comprised of octahedral and cuboctahedral cages and shows a rare (4,8)-connected scu topology. Gas adsorption studies of N2, H2 on the actived 1 at 77 K reveal a Langmuir surface area of 1707 m(2) g(-1), a BET surface area of 1555 m(2) g(-1), a total pore volume of 0.62 cm(3) g(-1), and a H2 uptake of 1.49 wt % at 1 bar and 3.05 wt % at 16 bar. CO2, CH4, and N2 adsorption studies at 195, 273, 285, and 298 K and also ideal adsorbed solution theory (IAST) calculations demonstrate that 1 has high selectivites of CO2 over CH4 and N2. The resulting framework represents a MOF with the highest gas uptakes and gas selectivities (CO2 over CH4 and N2) constructed by flexible ligands.

Microwave-assisted synthesis of a series of lanthanide metal-organic frameworks and gas sorption properties.

A series of isostructural microporous lanthanide metal-organic frameworks (MOFs) formulated as [Ln(2)(TPO)(2)(HCOO)]·(Me(2)NH(2))·(DMF)(4)·(H(2)O)(6) {Ln = Y (1), Sm (2), Eu (3), Gd (4), Tb (5), Dy (6), Ho (7), Er (8), Tm (9), Yb (10), and Lu (11); H(3)TPO = tris-(4-carboxylphenyl)phosphineoxide; DMF = N,N-dimethylformamide} has been synthesized under microwave-assisted solvothermal reaction for 30 min. Alternatively, if a conventional solvothermal reaction is carried out under the same temperature, a much longer time (3 days) is needed for the same phase in similar yield. Structure analysis reveals that the framework is a 4,8-connected network with point symbol (4(10)·6(16)·8(2)) (4(5)·6)(2), which is the subnet of alb net. Thermal gravimetric analyses performed on as-synthesized MOFs reveal that the frameworks have high thermal stability. The luminescent properties of 2, 3, 5, and 6 were investigated and show characteristic emissions for Sm(III), Eu(III), Tb(III), and Dy(III) at room temperature, respectively. Gas sorption properties of 1 and 3 were studied by experimentally measuring nitrogen, argon, carbon dioxide, methane, and hydrogen sorption isotherms. The resulting materials show high and preferential CO(2) adsorption over N(2) gas at ambient temperature, indicating that the present materials can be applied in a CO(2) capture process.

An Anion Metal–Organic Framework with Lewis Basic Sites-Rich toward Charge-Exclusive Cationic Dyes Separation and Size-Selective Catalytic Reaction

Organic dye pollutants become a big headache due to their toxic nature to the environment, and it should be one of the best solutions if we can separate and reuse them. Here, we report the synthesis and characterization of a microporous anion metal-organic framework (MOF) with Lewis basic sites-rich based on TDPAT (2,4,6-tris(3,5-dicarboxylphenylamino)-1,3,5-triazine) ligand, FJI-C2, which shows high adsorption and separation of cationic dye based on the charge-exclusive effect. Compared to other MOF materials, FJI-C2 shows the largest adsorption amount of methylene blue (1323 mg/g) at room temperature due to the nature of the anion frameworks and high surface area/pore volume. Furthermore, motivated by the adsorption properties of large guest molecules, we proceeded to investigate the catalytic behaviors of FJI-C2, not only because the large pore facilitates the mass transfer of guest molecules but also because the high density of Lewis basic sites can act as effective catalytic sites. As expected, FJI-C2 exhibits excellent catalytic performance for size-selective Knoevenagel condensation under mild conditions and can be reused several times without a significant decrease of the activity.

A Guest‐Dependent Approach to Retain Permanent Pores in Flexible Metal–Organic Frameworks by Cation Exchange

Two anionic metal-organic frameworks were successfully prepared based on pre-designed flexible multicarboxylate ligands and indium cations. Owing to the flexibility of the bridging organic linkers, which could not themselves sustain the frameworks, both of the frameworks showed thermal instability and shrinkage after removal of guest solvent molecules. Inspired by bamboo, we used a guest-dependent approach to tune the permanent porosity of the MOFs. In this approach, several tetraalkyammonium cations of different sizes were introduced into the channels by cation exchange to act as partitions and to support the main frameworks. This approach significantly enhanced the stability of the framework and its permanent porosity. Moreover, the gas-adsorption properties (such as gate sorption, hysteresis, and selectivity) of the MOFs were also modulated by the judicious choice of guest cations.

Direct CH Bond Arylation of Indoles with Aryl Boronic Acids Catalyzed by Palladium Nanoparticles Encapsulated in Mesoporous Metal–Organic Framework

Highly dispersed Pd nanoparticles encapsulated in the mesoporous metal–organic framework MIL‐101 demonstrated high activity and selectivity for the direct C2 arylation of various indoles with aryl boronic acids using O2 or 2,2,6,6‐tetramethylpiperidine N‐oxyradical as an external oxidant in acidic media under mild conditions. The green catalyst is easily recoverable and can be reused six times without leaching and loss of activity.

Pore-size tuning in double-pillared metal–organic frameworks containing cadmium clusters

Based on a double pillared strategy, four non-interpenetrated cadmium metal–organic frameworks, showing interesting luminescence properties, have been reported. It is interesting that the pore sizes can be continuously tuned and with the elongation of the pillars, the frameworks turn from nbo net to mot net for different layer stacking fashions.

Soluble Metal-Nanoparticle-Decorated Porous Coordination Polymers for the Homogenization of Heterogeneous Catalysis

Ultrasmall metal nanoparticles (MNPs) were decorated on soluble porous coordination polymers (PCPs) with high metal loadings. The solubility of the composite and the size of the MNPs can be controlled by varying the ratio of the precursors to the supports. The soluble PCPs can serve as a platform to homogenize heterogeneous MNPs catalysts, which exhibited excellent activity and recyclability in C-H activation and Suzuki reactions. This strategy combines the advantages of homogeneous and heterogeneous catalysis and may bring new inspiration to catalysis.

A bifunctional cationic porous organic polymer based on a Salen-(Al) metalloligand for the cycloaddition of carbon dioxide to produce cyclic carbonates

A bifunctional cationic porous organic polymer based on a Salen-(Al) metalloligand (Al-CPOP) containing imidazolium functionality exhibited enhanced activity and good recyclability in the cycloaddition of carbon dioxide to produce cyclic carbonates without the addition of co-catalysts at atmospheric pressure.

Syntheses, structures and photoluminescent properties of lanthanide coordination polymers based on pyridyl functionalized imidazole dicarboxylic acid

A series of lanthanide coordination polymers formulated as {[Ln2(HPIDC)2(H2O)8]·2(H2PIDC)·18H2O}n [Ln = Sm (1), Eu (2)], {[Dy2(HPIDC)2(H2O)9]·2(H2PIDC)·17H2O}n (3), {[Dy3(HPIDC)4(H2O)8]·(NO3)·6H2O}n (4), {[Dy2(HPIDC)2(bdc)(H2O)4]·8H2O}n (5), {[Ln(HPIDC)(bdc)]·H3O+·H2O}n [Ln = Er (6), Tm (7), Yb (8)] (H3PIDC = 2-(pyridin-4-yl)-1H-imidazole-4,5-dicarboxylic acid, H2bdc = 1,4-benzenedicarboxylic acid) based on pyridyl functionalized imidazole dicarboxylic acid ligand have been synthesized by hydrothermal methods and characterized by single crystal X-ray diffraction, powder X-ray diffraction, elemental analysis and thermogravimetric analysis. Compounds 1–3 are one-dimensional (1D) cationic chains linked by the H3PIDC ligands, and the free H2PIDC− act as counter ions in the crystal lattice. Compound 4 displays a 2D layer built up from 3-connected HPIDC2− ligands and 4-connected Dy(III) ions. While compounds 5–8 possess 2D network constructed from HPIDC2− and bdc2− ligands. The solid-state photoluminescent measurements show the photoluminescence of 1–5 are typical narrow emission bands of their lanthanide cations.