Controllable Generation of Reactive Oxygen Species on Cyano-Group-Modified Carbon Nitride for Selective Epoxidation of Styrene.

The controlled generation of reactive oxygen species (ROS) to selectively epoxidize styrene is a grand challenge. Herein, cyano-group-modified carbon nitrides (CNCY x and CN-T y ) are prepared, and the catalysts show better performance in regulating ROS and producing styrene oxide than the cyano-free sample. The in situ diffuse reflectance infrared and density functional theory calculation results reveal that the cyano group acts as the adsorption and activation site of oxygen. X-ray photoelectron spectroscopy and NMR spectrum results confirm that the cyano group bonds with the intact heptazine ring. This unique structure could inhibit H2O2 and ⋅OH formation, resulting in high selectivity of styrene oxide. Furthermore, high catalytic activity is still achieved when the system scales up to 2.7 L with 100 g styrene under solar light irradiation. The strategy of cyano group modification gives a new insight into regulating spatial configuration for tuning the utilization of oxygen-active species and shows potential applications in industry.

Enhanced photocatalytic hydrogen production from aqueous-phase methanol reforming over cyano-carboxylic bifunctionally-modified carbon nitride.

Polymeric carbon nitride is a promising candidate for metal-free photocatalysis, but it is hampered by low activity due to poor carrier separation efficiency and lack of active sites. We have constructed a bifunctionally-modified structure, containing cyano groups internally and carboxyl groups on the surface, that was about 205 times more active than unmodified carbon nitride. The internal cyano groups enhanced the photoelectric performance of carbon nitride, while the surface carboxyl groups acted as active sites to promote hydrogen production. It is anticipated that this work will inform the rational design of polymeric carbon nitride and inspire similar attempts to modify polymers.

One-pot selective synthesis of azoxy compounds and imines via the photoredox reaction of nitroaromatic compounds and amines in water.

A facile one-pot two-stage photochemical synthesis of aromatic azoxy compounds and imines has been developed by coupling the selective reduction of nitroaromatic compounds with the selective oxidation of amines in an aqueous solution. In the first stage (light illumination, Ar atmosphere), the light excited nitroaromatic molecule abstract H from amine to form ArNO2H and amine radical, which then form nitrosoaromatic, hydroxylamine and imine compounds. Water acts as a green solvent for the dispersion of the reactants and facilitates the formation of nitrosoaromatic and hydroxylamine intermediate compounds. In the second stage (no light, air atmosphere), the condensation of nitrosoaromatic and hydroxylamine compounds yields aromatic azoxy product with the aid of molecular oxygen in air. This photochemical synthesis achieved both high conversion and high product selectivity (>99%) at room temperature.

Synthesis of nitrogen-containing ordered mesoporous carbon as a metal-free catalyst for selective oxidation of ethylbenzene.

Nitrogen-containing ordered mesoporous carbon (NOMC) was synthesized by using m-aminophenol (MAP) as a carbon and nitrogen co-precursor via a co-assembly process with F127 in aqueous phase and exhibited a good catalytic performance for selective oxidation of ethylbenzene.

Covalently functionalized carbon nanotube supported Pd nanoparticles for catalytic reduction of 4-nitrophenol.

Carbon nanotubes (CNTs) were covalently functionalized via 1,3-dipolar cycloaddition reaction under microwave conditions. The functionalized CNTs were characterized by thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), N2 adsorption isotherms and Raman spectroscopy. The surface concentration of phenolic hydroxyl groups on the surface of CNTs was adjusted by varying the reaction temperature. In addition, we prepared Pd nanoparticle/CNT (Pd NP/CNT) nanocomposites through strong electrostatic adsorption and hydrogen reduction. The results indicated that the functional groups could not only improve the dispersion of CNTs in water, but also enhance the interaction between Pd precursors and CNTs, thus preventing small Pd NPs (average diameter of 1.5 nm) from agglomerating. Furthermore, the Pd NP/CNT-220 nanocomposites showed high catalytic activity for the reduction of 4-nitrophenol. The turnover frequency (TOF) of this catalyst was up to 18 min(-1), which was attributed to the small size and uniform distribution of Pd NPs on the surface of CNTs.

Surfactant-free hydrothermal synthesis of sub-10 nm γ-Fe2O3-polymer porous composites with high catalytic activity for reduction of nitroarenes.

Porous γ-Fe2O3-polymer composites were synthesized by a novel one-pot surfactant-free hydrothermal approach. The γ-Fe2O3-polymer composites consisting of 3.5 nm γ-Fe2O3 nanoparticles and porous polymers exhibited high catalytic activity and recycling performance in the reduction of nitroarenes.

Steric hindrance-dependent rational design and synthesis of three new Keggin-based supramolecular networks.

Three supramolecular architectures based on alpha-Keggin-type polyoxometalates have been synthesized hydrothermally, and their structures have been characterized by elemental analyses, infrared (IR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and single crystal X-ray diffraction structure analyses. [Ni(enMe)(2)(H(2)O)(2)](2)[Ni(enMe)(2)PW(VI)(9)W(V)(3)O(40)] x H(2)O (1) (enMe = 1,2'-propanediamine) exhibits a novel 2-D supramolecular sinusoidal layer through the interactions between transition metal complexes and 1-D covalent chains which are constructed from alpha-Keggin units bridged by transition metal complexes. [Ni(enMe)(2)](4){[Ni(enMe)(2)][Ni(enMe)(2)(H(2)O)AsW(VI)(6)W(V)(4)V(IV)(4)O(42)](2)} x 6 H(2)O (2), representing a 3-D supramolecular framework with 1-D channels, contains the first example of a tungstate dimer with inorganic-organic composite surfaces built up from [Ni(enMe)(2)](2+) cation bridges and bi-capped alpha-Keggin polyoxometalate building blocks supporting the transition metal complex. [Ni(enMe)(2)](4){[Ni(enMe)(2)][Ni(enMe)(2)(H(2)O)AsMo(VI)(4)Mo(V)(4)V(IV)(8)O(44)](2)} x 8 H(2)O (3), showing a 3-D supramolecular framework with 1-D channels, contains the first example of a molybdoarsenate dimer formed by [Ni(enMe)(2)](2+) cations bridging two neighboring tetra-capped alpha-Keggin-based molybdates that support the transition metal complex [Ni(enMe)(2)H(2)O]. The topological networks of the supramolecular frameworks of 2 and 3 are analogous. Crystal structural analysis reveals that the dimensionality and the organization of polyoxometalate building units in the solid state can be tuned by the steric hindrances of the polyanions. Both 2 and 3 exhibit intensive photoluminescence.