1502-47-2Relevant academic research and scientific papers
Use of melem as a nucleophilic reagent to form the triphthalimide C 6N7(phthal)3-New targets and prospects
Schwarzer, Anke,Boehme, Uwe,Kroke, Edwin
, p. 12052 - 12058,7 (2012)
Melem (1), as one of the most important representatives of the tri-s-triazine compounds, can be used as a nucleophilic reagent in reactions with phthalic acid derivatives. The synthesis of 2,5,8-triphthalimido-tri-s- triazine (C6N7(phthal)3, 2) was investigated starting from phthalic anhydride or phthalic dichloride in various solvents, at different temperatures as well as in the solid state. NMR measurements (solution and solid state), IR spectroscopy and elemental analysis indicated the formation of a cyclic imide. Single-crystal structure analysis of a 1:1 adduct of 2 with nitromethane proved the molecular structure expected for a phthalimido-s-heptazine. DFT calculations were performed to obtain a better insight into the structural features of compound 2, especially the interaction of the carbonyl groups with the tri-s-triazine nitrogen atoms. The title compound 2 shows promising properties: it is thermally stable up to 500 °C in air and shows strong photoluminescence with a maximum emission at around 500a nm. The potential of the nucleophilic reaction of melem with other strong electrophiles provides new targets and prospects. Copyright
Carbon nitride as a ligand: Edge-site coordination of ReCl(CO)3-fragments to g-C3N4
Coulson, Ben,Isaacs, Mark,Lari, Leonardo,Douthwaite, Richard E.,Duhme-Klair, Anne-K.
, p. 7450 - 7453 (2019)
IR spectroscopy and model structural studies show binding of ReCl(CO)3-fragments to carbon nitride (g-C3N4) occurs via κ2 N,N′ bidentate coordination.
Functionalizing carbon nitride with heavy atom-free spin converters for enhanced 1O2 generation
Wu, Wenting,Han, Congcong,Zhang, Qinhua,Zhang, Qinggang,Li, Zhongtao,Gosztola, David J.,Wiederrecht, Gary P.,Wu, Mingbo
, p. 222 - 229 (2018)
Carbon nitride as a metal-free conjugated polymer exhibits an intriguing prospect for the design of advanced photosensitizers for singlet oxygen (1O2) generation. However, the intersystem crossing (ISC) process is quite insufficient in carbon nitride, limiting the 1O2 generation. Here, we report a facile and general strategy to confined benzophenone as a heavy atom-free spin converter dopant in carbon nitride via the facile copolymerization. With proper energy level matching between the heavy atom-free spin converter and various ligands based on carbon nitride precursors, the proper combination can decrease the singlet-triplet energy gap (ΔEST) and hence generate 1O2 effectively. Due to its significant and selectivity for 1O2 generation, the as-prepared carbon nitride-based photosensitizer shows a high selective photooxidation activity for 1,5-dihydroxy-naphthalene (1,5-DHN). The product yield reached 71.8% after irradiation for 60 min, which was higher than that of cyclometalated PtII complexes (53.6%) in homogeneous photooxidation. This study can broaden the application of carbon nitride in the field of selective heterogeneous photooxidation due to simple operation, low cost, and high efficiency, making it a strong candidate for future industrialization.
Understanding the Surface of g-C3N4, an Experimental Investigation of the Catalytic Active Site on the Interface
Li, Qianqian,Jiang, Jing,Lin, Bin,Ding, De,Xu, Hai,Wang, Pingshan,Chen, Yin
, p. 3296 - 3303 (2019)
Abstract: g-C3N4 has shown poor photocatalytic activity without co-catalyst. Studies on the chemical and physical properties of the g-C3N4 surface can help to understand the way how co-catalyst species interact with g-C3N4. To identify the role of the surface NH2 group in the formation of heterojunction photo-catalysts, g-C3N4/Melem was functionalized by different alkyl groups and characterized systematically by NMR, IR, UV–Vis, XPS and TEM. The surface alkyl groups affected the coordination of the Pt ion with the surface, and a significant photo-catalysis activity decrease was observed in turn. The results disclosed that the terminal NH2 played an important role in the formation of the co-catalyst heterojunctions and the surface catalysis active sites, and provided experimental evidence to understand the reaction mechanism. Graphic Abstract: [Figure not available: see fulltext.]
Photophysics and Photocatalysis of Melem: A Spectroscopic Reinvestigation
Wen, Jing,Li, Ruiyu,Lu, Rong,Yu, Anchi
, p. 1060 - 1066 (2018)
Graphitic carbon nitride (g-CN) is one potential metal-free photocatalyst. The photocatalytic mechanism of g-CN is related to the heptazine ring building unit. Melem is the simplest heptazine-based compound and g-CN is its polymeric product. Thus, studies on the photophysical properties of melem will help to understand the photocatalytic mechanism of heptazine-based materials. Herein, the spectroscopic features of melem were systematically explored through measuring its absorption spectrum, fluorescence spectrum, and fluorescence decay. Both fluorescence spectroscopy and fluorescence decay measurements show that the condensation of melamine to melem causes stronger photoluminescence, whereas the condensation of melem to g-CN causes weaker photoluminescence. In addition, all observations reveal that a mixture of monomer melem and its higher condensates is more easily obtained during the preparation of melem, and that the higher condensates of melem affect the photophysical properties of melem dominantly. The photocatalytic hydrogen evolution of melem has also been measured and the monomer melem has negligible photoinduced water-splitting activity.
Low-molecular-weight carbon nitrides for solar hydrogen evolution
Lau, Vincent Wing-Hei,Mesch, Maria B.,Duppel, Viola,Blum, Volker,Senker, Jürgen,Lotsch, Bettina V.
, p. 1064 - 1072 (2015)
This work focuses on the control of the polymerization process for melon ( graphitic carbon nitride ), with the aim of improving its photocatalytic activity intrinsically. We demonstrate here that reduction of the synthesis temperature leads to a mixture of the monomer melem and its higher condensates. We show that this mixture can be separated and provide evidence that the higher condensates are isolated oligomers of melem. On evaluating their photocatalytic activity for hydrogen evolution, the oligomers were found to be the most active species, having up to twice the activity of the monomer/oligomer mixture of the as-synthesized material, which in turn has 3 times the activity of the polymer melon, the literature benchmark. These results highlight the role of defects , i.e., chain terminations, in increasing the catalytic activity of carbon nitrides and at the same time point to the ample potential of intrinsically improving the photocatalytic activity of carbon nitride , especially through the selective synthesis of the active phase. (Chemical Equation Presented).
Single-crystalline melem (C6N10H6) nanorods: A novel stable molecular crystal photocatalyst with modulated charge potentials and dynamics
Lei, Renbo,Du, Bingsheng,Lai, Xiaofang,Wu, Jing,Zhang, Zhihua,Liu, Shengwei,Wu, Rong,Li, Xin,Song, Bo,Jian, Jikang
, p. 13234 - 13241 (2019)
It is still challenging to control the crystallization and morphologies of molecular crystal nanostructures with excellent photocatalytic activities. In this study, single-crystalline melem (C6N10H6) nanorods (MNRs) were prepared by a facile thermal polymerization route under a flowing argon atmosphere. Compared with the bulk melem counterpart and g-C3N4, the MNRs exhibited substantially improved efficiency and stability towards the photodegradation of diverse organic pollutants including methyl orange, rhodamine B, and methylene blue. Moreover, the average photocatalytic hydrogen evolution rate of MNRs was about 2.6 folds higher than that of bulk melem under the same conditions. The enhanced photocatalytic redox performance of MNRs arises from the single-crystal nature and novel one-dimensional (1D) nanorod morphology, contributing to elevated conduction band potentials and promoting charge transport dynamics. This study not only reports single-crystalline melem 1D nanostructures as novel highly efficient and stable molecular-crystal photocatalysts, but also reveals the important roles of synergetic tuning of charge potentials and dynamics in enhancing the photocatalytic activity of molecular-crystal photocatalysts.
Melemium Methylsulfonates HC6N7(NH 2)SH2C6N7(NH2)S(SO 3Me)3·H2O and H2C 6N7(NH2)3(SO3Me) 2·H2O
Sattler, Andreas,Schoenberger, Stefanie,Schnick, Wolfgang
, p. 476 - 482 (2010)
Melem C6N7(NH2)3 was shown to form a variety of adduct phases and salts. Salts of melem can be yielded by reaction of melem with strong acids. We investigated the reaction of melem with methylsulfonic acid, thus identifying two new melemium salts with formulas HC6N7(NH2)3H2C 6N7(NH2)3(SO3Me) 3·H2O (1) and H2C6N 7(NH2)3-(SO3Me)2· H2O (2), respectively. The structures of both compounds were elucidated using single-crystal XRD compound 1: (P1 no. 2, Z = 2, a = 10.096(2), b = 12.865(3), c = 13.369(3) A, α = 63.28(3), β = 81.19(3), γ = 72.92(3)°, V = 1461.4(7) A3) compound 2: (P21/n, no. 14, Z = 4, a = 8.0757(16), b = 7.6937(15), c = 27.540(6) A, β = 92.03(3)°, V = 1710.6(6) A3). Both compounds are discussed in comparison to structural data from the literature of other melemium salts. We also present new synthetic approaches for the preparation of melem in larger quantities.
C3N5: A Low Bandgap Semiconductor Containing an Azo-Linked Carbon Nitride Framework for Photocatalytic, Photovoltaic and Adsorbent Applications
Kumar, Pawan,Vahidzadeh, Ehsan,Thakur, Ujwal K.,Kar, Piyush,Alam, Kazi M.,Goswami, Ankur,Mahdi, Najia,Cui, Kai,Bernard, Guy M.,Michaelis, Vladimir K.,Shankar, Karthik
, p. 5415 - 5436 (2019)
Modification of carbon nitride based polymeric 2D materials for tailoring their optical, electronic and chemical properties for various applications has gained significant interest. The present report demonstrates the synthesis of a novel modified carbon nitride framework with a remarkable 3:5 C:N stoichiometry (C3N5) and an electronic bandgap of 1.76 eV, by thermal deammoniation of the melem hydrazine precursor. Characterization revealed that in the C3N5 polymer, two s-heptazine units are bridged together with azo linkage, which constitutes an entirely new and different bonding fashion from g-C3N4 where three heptazine units are linked together with tertiary nitrogen. Extended conjugation due to overlap of azo nitrogens and increased electron density on heptazine nucleus due to the aromatic π network of heptazine units lead to an upward shift of the valence band maximum resulting in bandgap reduction down to 1.76 eV. XRD, He-ion imaging, HR-TEM, EELS, PL, fluorescence lifetime imaging, Raman, FTIR, TGA, KPFM, XPS, NMR and EPR clearly show that the properties of C3N5 are distinct from pristine carbon nitride (g-C3N4). When used as an electron transport layer (ETL) in MAPbBr3 based halide perovskite solar cells, C3N5 outperformed g-C3N4, in particular generating an open circuit photovoltage as high as 1.3 V, while C3N5 blended with MAxFA1-xPb(I0.85Br0.15)3 perovskite active layer achieved a photoconversion efficiency (PCE) up to 16.7%. C3N5 was also shown to be an effective visible light sensitizer for TiO2 photoanodes in photoelectrochemical water splitting. Because of its electron-rich character, the C3N5 material displayed instantaneous adsorption of methylene blue from aqueous solution reaching complete equilibrium within 10 min, which is significantly faster than pristine g-C3N4 and other carbon based materials. C3N5 coupled with plasmonic silver nanocubes promotes plasmon-exciton coinduced surface catalytic reactions reaching completion at much low laser intensity (1.0 mW) than g-C3N4, which showed sluggish performance even at high laser power (10.0 mW). The relatively narrow bandgap and 2D structure of C3N5 make it an interesting air-stable and temperature-resistant semiconductor for optoelectronic applications while its electron-rich character and intrasheet cavity make it an attractive supramolecular adsorbent for environmental applications.
Melem (2,5,8-triamino-tri-s-triazine), an important intermediate during condensation of melamine rings to graphitic carbon nitride: Synthesis, structure determination by x-ray powder diffractometry, solid-state NMR, and theoretical studies
Juergens, Barbara,Irran, Elisabeth,Senker, Juergen,Kroll, Peter,Mueller, Helen,Schnick, Wolfgang
, p. 10288 - 10300 (2003)
Single-phase melem (2,5,8-triamino-tri-s-triazine) C6N 7(NH2)3 was obtained as a crystalline powder by thermal treatment of different less condensed C-N-H compounds (e.g., melamine C3N3(NH2)3, dicyandiamide H4C2N4, ammonium dicyanamide NH 4[N(CN)2], or cyanamide H2CN2, respectively) at temperatures up to 450°C in sealed glass ampules. The crystal structure was determined ab initio by x-ray powder diffractometry (Cu Kα1: P21/c (No. 14), a = 739.92(1) pm, b = 865.28(3) pm, c = 1338.16(4) pm, β = 99.912(2)°, and Z = 4). In the solid, melem consists of nearly planar C6N7(NH2) 3 molecules which are arranged into parallel layers with an interplanar distance of 327 pm. Detailed 13C and 15N MAS NMR investigations were performed. The presence of the triamino form instead of other possible tautomers was confirmed by a CPPI (cross-polarization combined with polarization inversion) experiment. Furthermore, the compound was characterized using mass spectrometry, vibrational (IR, Raman), and photoluminescence spectroscopy. The structural and vibrational properties of molecular melem were theoretically studied on both the B3LYP and the MP2 level. A structural optimization in the extended state was performed employing density functional methods utilizing LDA and GGA. A good agreement was found between the observed and calculated structural parameters and also for the vibrational frequencies of melem. According to temperature-dependent x-ray powder diffractometry investigations above 560°C, melem transforms into a graphite-like C-N material.
