Herein we report the synthesis of a crystalline graphitic carbon nitride, or g-C(3)N(4), obtained from the temperature-induced condensation of dicyandiamide (NH(2)C(=NH)NHCN) by using a salt melt of lithium chloride and potassium chloride as the solvent. The proposed crystal structure of this g-C(3)N(4) species is based on sheets of hexagonally arranged s-heptazine (C(6)N(7)) units that are held together by covalent bonds between C and N atoms which are stacked in a graphitic, staggered fashion, as corroborated by powder X-ray diffractometry and high-resolution transmission electron microscopy.

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Covalent triazine frameworks (CTFs) are normally synthesized by ionothermal methods.T he harsh synthetic conditions and associated limited structural diversity do not benefit for further development and practical large-scale synthesis of CTFs.Herein we report anew strategy to construct CTFs (CTF-HUSTs) via apolycondensation approach,which allows the synthesis of CTFs under mild conditions from aw ide arrayo fb uilding blocks.I nterestingly,t hese CTFs displayalayered structure.T he CTFs synthesized were also readily scaled up to gram quantities.T he CTFs are potential candidates for separations,p hotocatalysis and for energy storage applications.I np articular,C TF-HUSTs are found to be promising photocatalysts for sacrificial photocatalytic hydrogen evolution with am aximum rate of 2647 mmol h À1 g À1 under visible light. We also applied ap yro-lyzed form of CTF-HUST-4 as an anode material in asodium-ion battery achieving an excellent discharge capacity of 467 mAh g À1. Covalent organic frameworks (COFs) are an emerging class of porous materials,characterized by their ordered structures, high surface areas,and structural diversity. [1] They have shown promise in applications such as gas adsorption, [2] catalysis, [3] and optoelectronics. [4] Av ariety of methods have been reported to prepare COFs,s uch as polycondensation, [1a, 4a] cyclization reactions, [5] or surface mediated methods. [1b, 6] Covalent triazine frameworks (CTFs) are related to COFs and are typically constructed through cyclization reaction of nitrile aromatic building blocks;t hey feature high physico-chemical stability and high nitrogen content. [5, 7] Because of these characteristics,CTFs have found diverse applications in gas adsorption and storage, [5a, 7a,b] catalysis, [7c-e] and energy storage. [7f,g] There are still, however, al imited number of approaches for the synthesis of CTFs. [5a, 7a] Themost common approach is ionothermal synthesis at high temperatures (! 400 8 8C), which also requires alarge amount of ZnCl 2 to serve as both catalyst and reaction medium. [5a] This method can lead to CTFs with ad egree of crystalline order,b ut the high reaction temperatures cause the partial carbonization of the structure and the materials are obtained in the form of black powders.H ence,C TFs prepared by this method lack an electronic band gap and may be unsuitable for photophysical applications.F urthermore,t hese reaction temperatures consume alarge amount of energy and preclude all but the most stable building blocks,thus limiting the scope for scale up and synthetic diversity.I ti s, therefore,i mperative to find new methods for the synthesis of CTFs under milder conditions. Previous research has shown that CTFs could be synthesized at room temperature,a nd catalyzed by strong and corrosive acid such as trifluoromethylsufonic acid. [7a,b] This avoids carbonization, but the method is obviously not suitable to acid-sensitive building blocks,and also the resulting materials did not have layered structures. Here,wedevelop anew strategy involvi...

Graphitic carbon nitride has been predicted to be structurally analogous to carbon-only graphite, yet with an inherent bandgap. We have grown, for the first time, macroscopically large crystalline thin films of triazine-based, graphitic carbon nitride (TGCN) using an ionothermal, interfacial reaction starting with the abundant monomer dicyandiamide. The films consist of stacked, two-dimensional (2D) crystals between a few and several hundreds of atomic layers in thickness. Scanning force and transmission electron microscopy show long-range, in-plane order, while optical spectroscopy, X-ray photoelectron spectroscopy, and density functional theory calculations corroborate a direct bandgap between 1.6 and 2.0 eV. Thus TGCN is of interest for electronic devices, such as field-effect transistors and light-emitting diodes.

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A novel covalent triazine framework (CTF-0) was prepared by trimerization of 1,3,5-tricyanobenzene in molten ZnCl 2 . The monomer/ ZnCl 2 ratio, the reaction time, and temperature significantly influence the structure and porosity of such networks. XRD measurements revealed that crystalline frameworks can be formed with surface areas around 500 m 2 •g −1 and high CO 2 uptakes. Increasing the reaction temperature yielded an amorphous material with an enlarged surface area of 2000 m 2 •g −1 . This material showed good catalytic activity for CO 2 cycloaddition.

Inspired by geological ore formation processes, we apply one-step hydrothermal (HT) polymerization to the toughest existing high-performance polymer, poly(p-phenyl pyromellitimide) (PPPI). We obtain highlyordered and fully imidized PPPI as crystalline flakes and flowers on the micrometer scale. In contrast to classical 2-step procedures that require long reaction times and toxic solvents and catalysts, HT polymerization allows for full conversion in only 1 h at 200 C, in nothing but hot water. Investigation of the crystal growth mechanism via scanning electron microscopy (SEM) suggests that PPPI aggregates form via a dissolution-polymerization-crystallization process, which is uniquely facilitated by the reaction conditions in the HT regime. A conventionally prefabricated polyimide did not recrystallize hydrothermally, indicating that the HT polymerization and crystallization occur simultaneously. The obtained material shows excellent crystallinity and remarkable thermal stability (600 C under N 2 ) that stem from a combination of a strong, covalent polymer backbone and interchain hydrogen bonding.

Lithiated graphitic carbon nitride (C3N4) was fabricated by electrochemical and solid-state reactions. The addition of Li to C3N4 results in a reaction between the Li and the graphite-like C3N species in C3N4. This irreversible reaction leads to the formation of Li-CHNR and Li-NCR2 species, which are detrimental to anode properties. Suitable nitrogen-doped carbon structures for anode applications are predicted to need high concentrations of pyridinic C–N–C terminal bonds and low concentrations of quaternary C3N species to boost electronic conductivity and reversibly cycle Li ions.