Stacked Covalent Organic Ribbons Perpendicular to Graphene Oxide Sheets; a 1D-p-2D Design for Photocatalytic Tandem Reactions.

Development of one dimensional covalent organic frameworks (1D-COFs) with potential in light absorption and catalysis is still challenging, due to their rapid interpenetration to form 2D and 3D porous structures. Here we report a successful synthesis of imine-linked 1D covalent organic ribbons (COR), using two simple linear building blocks 1,4-Benzenediamine (Bda) and [2,2'-Bipyridine]-5,5'-dicarbaldehyde (Bpy). The obtained 1D structure with nanorod morphology could keep its physicochemical characteristic properties when it is perpendicular to the surface of graphene oxide (GO) sheets (1D-p-2D structure). Due to an AB π- π stacking and efficient charge transfer between perpendicular 1D COR and GO sheets, the obtained nanocomposite showed strong visible light absorbance (400-700 nm) with coefficient of 4.400 M-1 cm-1 and decreased recombination rate of photogenerated reactive species by 92 %. The strategy of 1D-p-2D light driven system greatly enhanced the photocatalytic activity in practical applications such as both oxidation and hydrogenation tandem reactions to a rate constant of higher than 0.02 min-1 . This study presents the first case of 1D covalent organic polymers grown perpendicularly on a carbon-based layer for boosting electron mobility through the junction between the two components.

Electron flux at the Schottky junction of Bi NPs and WO3-supported g-C3N4: an efficient ternary S-scheme catalyst for removal of fluoroquinolone-type antibiotics from water.

Recently, global-scale attempts have been conducted to develop clean technologies and affordable materials to remediate pharmaceutical contaminants of water resources that are resistant to the biodegradation. In line with global efforts, this study reports a facile method to fabricate Bi nanocrystals in situ decorated on WO3 nanoplates and its composite with graphitic carbon nitride (WO3/Bi/g-C3N4) for photocatalytic degradation of fluoroquinolone-type antibiotics (ciprofloxacin and ofloxacin). The designed ternary S-scheme WO3/Bi/g-C3N4 composite material was fully characterized by physicochemical and electrochemical analysis. Depositing the cost-effective and earth-abundant Bi nanocrystals onto WO3 via a facile reduction route has been shown to increase the boosting of electron flux at their interface (Schottky junction). The S-scheme separation is confirmed by the calculation of band positions and the analysis of photogenerated hydroxyl radicals and holes. The complete removal of contaminants was obtained over the WO3/Bi/g-C3N4 photocatalyst after 90 min under visible light irradiation. The present work would provide a rational route for developing Bi NP-based photocatalysis to replace metallic Au, Pt, and Ag NPs.

Sub-level engineering strategy of nitrogen-induced Bi2O3/g-C3N4: a versatile photocatalyst for oxidation and reduction.

Herein, the α-Bi2O3 nanocrystal decorated by nitrogen dopant and its heterojunction nanocomposite with g-C3N4 (N0.1/Bi2O3/g-C3N4) is successfully fabricated for the first time, for photo-oxidation of RhB and photo-reduction of Cr(VI) to Cr(III). The resulting N0.1/Bi2O3/g-C3N4 (3%) nanocomposite showed an optimal Cr(VI) photo-reduction and RhB photo-oxidation rates under visible-light irradiation, being 3-4 times higher than that of pure α-Bi2O3. The results from XPS confirmed the substitution of nitrogen with various oxidation states from N3+ to Nx+ (x < 5), due to the existence of different nitrogen oxides including N-O, O-N=O, and NO3- in the crystal structure. We investigated the reaction mechanism using catalytic tests, impedance spectroscopy, EPR technique, and density functional calculations. The DFT calculations presented the appearance of a new mid-gap hybrid of p states, comprised of N 2p, O 2p, and Bi 6P states, which enhance light absorption capacity and narrow band gap. The theoretical results were in excellent agreement with experimental UV-Vis data. The N0.1/Bi2O3/g-C3N4 nanocomposite exhibited acceptable practical application value and recycling ability for removal of the contaminants. Such improved photocatalytic activity is originated from the modified band positions, new electron evolution pathway, introducing defects in α-Bi2O3 by insertion of N atoms into the Bi sites, and the enhanced charge carrier mobility between N0.1/Bi2O3 and g-C3N4. The strategy to form nitrogen-doped bismuth-based nanocomposites may open a new opportunity to design atomic-level electronic defects by feasible methods to obtain a versatile photocatalyst material with simultaneous photo-reduction and photo-oxidation ability for removal of Cr(VI) and organic dyes from water.

Photodegradation of 2,4-dichlorophenol by supported Pd(X2) catalyst (X = Cl, Br, N3): a HOMO manipulating point of view.

Three different palladium(II) complexes with ligands containing nitrogenized aromatic rings were investigated theoretically as model to obtain the computational band gap energies. The results demonstrated promising possibility for designing palladium(II) complexes with photocatalytic properties at visible light irradiation. Deliberated products were synthesized via grafting on the silica-coated Fe3O4 magnetic nanoparticles (Fe3O4@SiO2). Formation of complexes on the surface of Fe3O4@SiO2, as insoluble and reusable photocatalysts, was proved by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric (TGA), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometer (VSM), transmission electron microscope (TEM), and scanning electron microscopy (SEM) analyses. The trend of the band gap energies of prepared structures was calculated via experimental and theoretical methods. The photocatalytic capability of these nanoparticles was investigated in degradation of 2,4-dichlorophenol by means of HPLC analysis. A tentative reaction mechanism for the formation of intermediates was proposed. Graphical abstract ᅟ.