Search

Polymeric carbon nitride was synthesized from urea and doped with Cu and Fe to act as co-catalysts. The material doped with Fe was a new composite material composed of Fe(III) oxides (acting as a co-catalyst) wrapped by the polymer layers and amorphous carbon. Furthermore, the copper doped material was described in a previous report. The photocatalytic degradation of the azo dye direct blue 1 (DB) was studied using as photocatalysts: pure carbon nitride (CN), carbon nitride doped with Cu (CN-Cu) and carbon nitride doped with Fe (CN-Fe). The catalysts were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), by X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller method (BET), etc. The adsorption phenomenon was studied using the Langmuir and Freundlich models. For the kinetic study, a solution of 500 mg L−1of DB1 was treated with each catalyst, visible light and H2O2. The dye concentration was measured by spectrophotometry at the wavelength of 565 nm, and the removal of the total organic content (TOC) was quantified. BET analysis yielded surface areas of 60.029, 20.116 and 70.662 m2g−1for CN, CN-Cu and CN-Fe, respectively. The kinetics of degradation were pseudo-first order, whose constants were 0.093, 0.039 and 0.110 min−1for CN, CN-Cu and CN-Fe, respectively. The total organic carbon (TOC) removal reached the highest value of 14.46% with CN-Fe. [ABSTRACT FROM AUTHOR]

Polymeric carbon nitride doped with copper through a solid-state reaction was characterized by several techniques, among them are UV-visible spectroscopy, infrared spectroscopy, X-ray photoelectron spectroscopy, etc. The material is a semiconductor with a wide band gap of 2.74 eV. Sites of both Cu(I) and Cu(II) were detected, apparently only coordinated by the polymer. The material comprises crumpled nanosheets, and is substantially an amorphous layered material with a prevalent 2D structure with low inter-planar interactions, as shown by X-ray diffractometry and TeraHertz spectroscopy. Photo-oxidation of benzyl alcohol was used to probe the active sites of the material, comparing them with the non-doped material. The higher activity and selectivity toward salicylic alcohol of the non-doped material can be due to both a more localized electron transfer and a longer lifetime of the hole–electron pair. Cu-CN favored the oxidation of hydroxymethyl group. Therefore, the presence of copper can favor different reaction pathways with respect to the non-doped material. [ABSTRACT FROM PUBLISHER]

A new carbon-nitrogen organic semiconductor has been synthesized by pyrolysis of uric acid. This layered carbon-nitrogen material contains imidazole-, pyridine (naphthyridine)- and graphitic-like nitrogen, as evinced by infrared and X-ray photoelectron spectroscopies. Quantum chemistry calculations support that it would consist of a 2D polymeric material held together by hydrogen bonds. Layers are stacked with an interplanar distance between 3.30 and 3.36 Å, as in graphite and coke. Terahertz spectroscopy shows a behavior similar to that of amorphous carbons, such as coke, with non-interacting layers. This material features substantial differences from polymeric carbon nitride, with some characteristics closer to those of nitrogen-doped graphene, in spite of its higher nitrogen content. The direct optical band gap, dependent on the polycondensation temperature, ranges from 2.10 to 2.32 eV. Although in general the degree of crystallinity is low, in the material synthesized at 600 °C some spots with a certain degree of crystallinity can be found. [ABSTRACT FROM AUTHOR]

The adduct of melamine and cyanuric acid (MCA) was used in past research to produce polymeric carbon nitride and precursors. The reaction yield was considerably incremented by the addition of sulfuric acid. The polymeric carbon nitride formation occurs around 450 °C at temperatures above the sublimation of the adduct components, which occurs around 400 °C. In this report the effect of sulfuric acid on MCA was investigated. It was found that the MCA rosette supramolecular channel structures behave as a solid solvent able to host small molecules, such as sulfuric acid, inside these channels and interact with them. Therefore, the sulfuric acid effect was found to be close to that of a solute that causes a temperature increment of the “solvent sublimation” enough to allowing the formation of polymeric carbon nitride to occur. Sulfate ions are presumably hosted in the rosette channels of MCA as shown by simulations. [ABSTRACT FROM AUTHOR]