Xiaoming Liu

Enhanced carbon dioxide uptake by metalloporphyrin-based microporous covalent triazine framework

A class of metal functional microporous covalent triazine frameworks was prepared using a metalloporphyrin as a single building block, which is insoluble in common organic solvents and water, and can remain stable up to 500 °C under nitrogen atmosphere. According to the nitrogen physisorption isotherms, the highest Brunauer–Emmett–Teller specific surface area up to 1510 m2 g−1 was obtained for the new polymer framework with a pore volume of 2.674 cm3 g−1. The polymer framework displays excellent carbon dioxide uptake capacity (up to 13.9 wt%) at 273 K and 1 bar, which is influenced significantly by the porosity of the frameworks and functional activated sites in the skeletons.

Gas uptake, molecular sensing and organocatalytic performances of a multifunctional carbazole-based conjugated microporous polymer

A multifunctional carbazole-based conjugated microporous polymer MFCMP-1 is successfully prepared by oxidative coupling polymerization using a single monomer and structurally characterized. A new three-dimensional π-conjugated polymer framework can be combined with permanent microporous, highly luminescent properties and abundant nitrogen activated sites in the skeleton. It possesses a large BET surface area of over 840 m2 g−1 with a pore volume of 0.52 cm3 g−1, and displays a high carbon dioxide uptake capacity (up to 3.69 mmol g−1) at 273 K and 1 bar, with good selectivity towards CO2 over N2 and CH4. MFCMP-1 exhibits also strong fluorescent emission at 529 nm after excitation at 380 nm in THF solution and works as a luminescent chemosensor towards hazardous and explosive molecules, such as nitrobenzene, 2-nitrotoluene, and 2,4-dinitrotoluene. In addition, MFCMP-1 features a high concentration of Lewis base nitrogen sites on its internal surfaces; it thus acts as a highly efficient recyclable heterogeneous organocatalyst towards Knoevenagel reaction of malononitrile with aromatics, heterocyclic aldehydes, and cyclic ketones. Furthermore, we further highlight that the ease of synthesis and low cost, coupled with multifunctional properties, make MFCMP-1 an attractive functional material in practical applications.

An Azine‐Linked Covalent Organic Framework: Synthesis, Characterization and Efficient Gas Storage

A azine-linked covalent organic framework, COF-JLU2, was designed and synthesized by condensation of hydrazine hydrate and 1,3,5-triformylphloroglucinol under solvothermal conditions for the first time. The new covalent organic framework material combines permanent micropores, high crystallinity, good thermal and chemical stability, and abundant heteroatom activated sites in the skeleton. COF-JLU2 possesses a moderate BET surface area of over 410 m(2)  g(-1) with a pore volume of 0.56 cm(3)  g(-1) . Specifically, COF-JLU2 displays remarkable carbon dioxide uptake (up to 217 mg g(-1) ) and methane uptake (38 mg g(-1) ) at 273 K and 1 bar, as well as high CO2 /N2 (77) selectivity. Furthermore, we further highlight that it exhibits a higher hydrogen storage capacity (16 mg g(-1) ) than those of reported COFs at 77 K and 1 bar.

Triarylboron-Linked Conjugated Microporous Polymers: Sensing and Removal of Fluoride Ions.

A luminescent conjugated microporous polymer (BCMP-3) has been synthesized in high yield by a carbon-carbon coupling reaction using triarylboron as a building unit. BCMP-3 was fully characterized by using powder X-ray diffraction analysis, Fourier transform infrared spectroscopy, (13) C solid-state NMR spectroscopy, field emission scanning electron microscopy, thermogravimetric analysis, and nitrogen and carbon dioxide adsorption. The new three-dimensional conjugated framework possess a high Brunauer-Emmett-Teller (BET) specific surface area up to 950 m(2)  g(-1) with a pore volume of 0.768 cm(3)  g(-1) , good stability, and abundant boron sites in the skeleton. Under excited-light irradiation, BCMP-3 exhibits strong fluorescent emission at 488 nm with a high absolute quantum yield of 18 % in the solid state. Polymer BCMP-3 acts as a colorimetric and fluorescent chemosensor with high sensitivity and selectivity for F(-) over other common anions. In addition, the polymer also works as an adsorbent for F(-) removal and shows good adsorption capacities of up to 24 mg g(-1) at equilibrium F(-) concentrations of 16 mg L(-1) and a temperature of 298 K. The adsorption kinetics and isotherm were analyzed by fitting experimental data with pseudo-second-order kinetics and Langmuir equations. Furthermore, we highlight that BCMP-3 is an adsorbent for fluoride removal that can be efficiently reused many times without loss of adsorption efficiency.

A metallosalen-based microporous organic polymer as a heterogeneous carbon–carbon coupling catalyst

A novel microporous organic polymer framework with built-in metal sites in the skeleton has been synthesized by the Sonogashira–Hagihara reaction using salen-palladium as building units. The new microporous organic polymer possesses a high BET surface area, large pore volume, good stability and acts as a highly efficient robust recyclable heterogeneous catalyst towards carbon–carbon coupling reactions with low catalyst loading.

A porphyrin-linked conjugated microporous polymer with selective carbon dioxide adsorption and heterogeneous organocatalytic performances

A new porphyrin-based conjugated microporous polymer with rich nitrogen sites in the skeleton has been synthesized by alkyne–alkyne homocoupling reaction. The Brunauer–Emmett–Teller specific surface area up to 662 m2 g−1 was obtained for the new polymer framework with a pore volume of 0.55 cm3 g−1. The polymer network displays high carbon dioxide uptake capacity (up to 3.58 mmol g−1) at 273 K and 1 bar, with good selectivity towards CO2 over N2 and CH4. Furthermore, this framework also acts as a solid organocatalyst towards Knoevenagel reaction of malononitrile with aromatic, heterocyclic aldehydes, and cyclic ketones. The reaction afforded the corresponding products in excellent yields (up to 99%) with short times. Moreover, the heterogeneous catalyst was also found to exhibit an excellent recyclability (up to 10 times) without loss of efficiency.

Chromium complexes supported by phenanthrene-imine derivative ligands: synthesis, characterization and catalysis on isoprene cis-1,4 polymerization.

Reactions of CrCl(2)(THF)(2) with N-aryl-9,10-iminophenanthraquinone in CH(2)Cl(2) give the monoimine chromium complexes (Ar)IPQCrCl(2)(THF)(2) (1, Ar = 2,6-Me(2)C(6)H(3); 2, Ar = 2,6-Et(2)C(6)H(3); 3, Ar = 2,6-(i)Pr(2)C(6)H(3)). Molecular structures of 1 and 3 were revealed to be monomeric with the chromium atoms in distorted octahedral geometries. Similar reactions of CrCl(2)(THF)(2) with N,N-bis(arylimino)phenanthrene ligands afford the diimine complexes (Ar1,Ar2)BIPCrCl(μ-Cl)(3)Cr(THF)(Ar1,Ar2)BIP (4, Ar(1) = Ar(2) = 2,6-Me(2)C(6)H(3); 5, Ar(1) = Ar(2) = 2,6-Et(2)C(6)H(3); 6, Ar(1) = Ar(2) = 2,6-(i)Pr(2)C(6)H(3); 7, Ar(1) = 2,6-Me(2)C(6)H(3), Ar(2) = 2,6-(i)Pr(2)C(6)H(3)). The X-ray diffraction analysis shows that 4, 5, and 7 are chlorine-bridged dimers with each chromium atom in a distorted octahedral geometry. Upon activation with MAO, all these complexes exhibit good catalytic activities for isoprene polymerization affording polyisoprene with predominantly a cis-1,4 unit.

Metalloporphyrin‐Based Hypercrosslinked Polymers Catalyze Hetero‐Diels–Alder Reactions of Unactivated Aldehydes with Simple Dienes: A Fascinating Strategy for the Construction of Heterogeneous Catalysts

We describe a novel and intriguing strategy for the construction of efficient heterogeneous catalysts by hypercrosslinking catalyst molecules in a one-pot Friedel-Crafts alkylation reaction. The new hypercrosslinked polymers (HCPs) as porous solid catalysts exhibit the combined advantages of homogeneous and heterogeneous catalysis, owing to their high surface area, good stability, and tailoring of catalytic centers on the frameworks. Indeed, a new class of metalloporphyrin-based HCPs were successfully synthesized using modified iron(III) porphyrin complexes as building blocks, and the resulting networks were found to be excellent recyclable heterogeneous catalysts for the hetero-Diels-Alder reaction of unactivated aldehydes with 1,3-dienes. Moreover, this new strategy showed wide adaptability, and many kinds of homogeneous-like solid-based catalysts with high catalytic performance and excellent recyclability were also constructed.

Triarylboron-based fluorescent conjugated microporous polymers

Novel triarylboron-based conjugated microporous polymers (BCMPs) were successfully synthesized and characterized, which are insoluble in common organic solvents and water, and can keep stable up to 310 °C under a nitrogen atmosphere. According to the nitrogen physisorption isotherms, the Brunauer–Emmett–Teller specific surface area values for these porous materials vary between 815 and 911 m2 g−1. Two polymer frameworks display good carbon dioxide uptake capacity at 273 K and 1 bar. These materials might find applications in organic electronics and sensing technologies.

Robust porous organic polymers as efficient heterogeneous organo-photocatalysts for aerobic oxidation reactions

Metal-free, visible-light active and heterogeneous organic photocatalysts offer a more sustainable and environmentally friendly alternative to traditional metal-based catalysts. Here a porous organic hyper-crosslinked polymer, CF-HCP, was successfully synthesized through a facile and cost-effective process. The chemical and structural properties of CF-HCP were fully characterized by using powder X-ray diffraction analysis, Fourier transform infrared spectroscopy, 13C solid-state NMR spectroscopy, electron microscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy and nitrogen adsorption. The new three-dimensional hyper-crosslinked network possesses a high Brunauer–Emmett–Teller (BET) specific surface area up to 1200 m2 g−1 with a pore volume of 0.92 cm3 g−1, and exhibits good thermal, chemical and photochemical stability. Importantly, CF-HCP was found to be a highly effective heterogeneous photocatalyst for a wide range of organic reactions, including the oxidative coupling of primary amines, dehydrogenation of nonactive secondary amine substrates, and selective oxidation of sulfide under visible-light irradiation and using molecular oxygen as a clean oxidant. In particular, mild reaction conditions, ease of product separation by simple filtration, significant recyclability and low cost make this network material an economical and eco-friendly catalyst for the preparation of versatile organic compounds.