Synthesis of inorganic heptazine-based materials

Abstract

This dissertation describes research on the synthesis and characterization of extended heptazine-based, graphite-like carbon nitride materials (CN x), as well as molecular heptazine (C 6 N 7) derivatives. Spurred on by recent triazine to heptazine conversion studies, a structural examination was performed on an amorphous nitrogenrich carbon nitride material formed via the rapid and exothermic self-propagating decomposition of a triazine (C 3 N 3) precursor, trichloromelamine (TCM). The thermally stable and insoluble CN x H y product was determined to be composed of heptazine repeat units. This conclusion was supported by 13 C solid state NMR and isolation of molecular heptazine anions after base hydrolysis (structural deconstruction) of the CN x H y material. Modifications to the decomposition of TCM were explored. Introduction of a solid template (NaCl or silica) led to morphological changes in the TCM-CN x product, observed by scanning electron microscopy. It was found that the sodium salts, NaBr and NaN 3 , led to chloride exchange with TCM. The use of mixtures of NH 4 Cl and NaN 3 also showed changes in the morphology of the material, while leading to slight changes in the IR spectra. A series of reactions between NaBH 4 and TCM yield novel thermally stable boron carbon nitride (BCN) materials. Reactions between TCM and Li 2 C 2 or aromatic organic solids led to CN x materials with increased carbon contents. Crystalline metal-heptazine precipitates were generated by cation exchange reaction with the base hydrolysis product of TCM-CN x , potassium cyamelurate. A structure solution was attempted for the crystalline copper cyamelurate salt, KCu[C 6 N 7 O 3 ]•4H 2 O. Neutral molecular heptazines were also synthesized; these species included 2,5,8-tribromo-s-heptazine (TBH), 2,5,8-triphenyl-s-heptazine (TPH), 2,5,8ix Solid state NH 4 Cl/NaN 3 and NaHCO 3 incorporation into trichloromelamine decomposition: Gas-forming additives .

K3C6N7O3·2H2O: A Multifunctional Nonlinear Optical Cyamelurate Crystal with Colossal π-Conjugated Orbitals

“…In addition, I exhibit a broadband UV photoluminescence around 366 nm under an excitation of 306 nm. The full width at half-maximum (fwhm) of the emission spectrum is about 60 nm, which is comparable to that in a previous report in A 3 (C 6 N 7 O 3 ) (A= Li, Na, K, Rb, Cs; fwhm ∼50 nm) and smaller than in K 3 (C 6 N 7 O 3 )·3H 2 O (fwhm ∼250 nm) . Such a wide emission and long fluorescence trailing beyond 450 nm could be originated from the electron–phonon coupling effect.…”

A Rational Design of Microporous Nitrogen-Rich Lanthanide Metal–Organic Frameworks for CO2/CH4 Separation

“…Cyamelurate linker (Cy) was prepared according to the reported method. 26 It based on three fused rings of six CN bonds, which surround a central sp 2 -hydribized N-atom and three oxygen atoms negatively charged in the external to form a flat cross-conjugated aromatic system. This compound is known to be thermally very stable and possess interesting chemical properties.…”

“…Potassium cyamelurate (Cy) was synthesized according to the method described in the literature . A mixture of Cy (0.05 mmol), Ln­(NO 3 ) 3 ·6H 2 O (0.15 mmol), DMF (6 mL), and H 2 O (6 mL) were stirred thoroughly followed by sonication for 10 min.…”

“…Potassium cyamelurate (Cy) was synthesized according to the method described in the literature. 26 A mixture of Cy (0.05 mmol), Ln(NO 3 ) 3 •6H 2 O (0.15 mmol), DMF (6 mL), and H 2 O (6 mL) were stirred thoroughly followed by sonication for 10 min. The resulting solution were sealed in a scintillation vial, which was heated at 80 °C for 24 h, and then cooled slowly to room temperature at a rate of 10 °C/h.…”

Kinetic and Thermodynamic Control in Rare Earth Cyamelurates Synthesis

“…For example, we isolated manganese cyamelurate KMn(C 6 N 7 O 3 )•5H 2 O [8], the composition and diffraction pattern of which is similar to the results of the work [9], but different from the crystals described in [6]. On the other hand, samples of cobalt cyamelurate synthesized in [9] and [8] are divers: energy dispersive spectroscopy indicates the absence of potassium cations in the cobalt cyamelurate sample [9], whereas in our case the composition corresponds to KCo(C 6 N 7 O 3 )•5H 2 O [8]. Most likely, the reaction time, which was various in these three works, is the main parameter determining the synthesis of a particular substance.…”