Synthesis and Photocatalytic Activity of Poly(triazine imide)

Abstract

Poly(triazine imide) was synthesized with incorporation of Li(+) and Cl(-) ions (PTI/Li(+)Cl(-)) to form a carbon nitride derivative. The synthesis of this material by the temperature-induced condensation of dicyandiamide was examined both in a eutectic mixture of LiCl-KCl and without KCl. On the basis of X-ray diffraction measurements of the synthesized materials, we suggest that a stoichiometric amount of LiCl is necessary to obtain the PTI/Li(+)Cl(-) phase without requiring the presence of KCl at 873 K. PTI/Li(+)Cl(-) with modification by either Pt or CoO(x) as cocatalyst photocatalytically produced H(2) or O(2), respectively, from water. The production of H(2) or O(2) from water indicates that the valence and conduction bands of PTI/Li(+)Cl(-) were properly located to achieve overall water splitting. The treatment of PTI/Li(+)Cl(-) with [Pt(NH(3))(4)](2+) cations enabled the deposition of Pt through ion exchange, demonstrating photocatalytic activity for H(2) evolution, while treatment with [PtCl(6)](2-) anions resulted in no Pt deposition. This was most likely because of the preferential exchange between Li(+) ions and [Pt(NH(3))(4)](2+) cations.

Low-Molecular-Weight Carbon Nitrides for Solar Hydrogen Evolution

“…For example, melam (triazinetriazine dimer, Scheme S1) is a short-lived intermediate in the synthesis of melem, 15 while polymers of triazine are not expected to form unless under ionothermal conditions. 39 Characterization of the spent as-synthesized catalyst after the photocatalytic reaction showed the formation of a melem hydrate phase, 38 as evident in the XRD patterns, but virtually no change in the IR spectra, from both the 8 h and the 129 h experiments ( Figure S5 and S6 respectively). The hydrate phase is likely formed from the recrystallization of the monomers present in the sample under the aqueous conditions of the photocatalytic reaction, rather than depolymerization of the higher conden- 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 sation species, since the IR absorption bands corresponding to the bridging secondary amines are still present.…”

“…15,[35][36][37][38] Recent results have shown that not only are triazine polymers active for photocatalytic hydrogen and oxygen evolution, but also chemical modifications can enhance their activity to values even exceeding that of the heptazine polymer, melon. 39,40 Another sparsely explored topic concerns the fundamental properties of these carbon nitride materials, particularly the nature of the active species, its mechanistic operation, and strategies to intrinsically improve their activity, rather than extrinsically by red-shifting the absorption through doping and increasing the surface area through morphology control. Since highly crystalline melem and melon, obtainable only by synthesis in closed ampules under an autogenous pressure of ammonia (which induces partial de-and repolymerization, thereby leading to defect healing 14 ), have negligible photocatalytic activity, the currently accepted postulate is that "surface terminations and defects seem to be the real active sites".…”

Dendritic Tip-on Polytriazine-Based Carbon Nitride Photocatalyst with High Hydrogen Evolution Activity

“…The use of the molten salt state of the LiCl/KCl mixture at high temperature led to crystalline polymers comprising triazine building units. 54 The details of our optimization attempt at the supramolecular formation step are described in the SI ( Table S1). …”

Carbon- and Nitrogen-Based Porous Solids: A Recently Emerging Class of Materials

“…42,47,48 The use of the starting monomer DCDA in LiBr/KBr molten mixture leads to form TGCN at 600°C for 60 h. 41 Theoretical investigation on TGCN indicates that this material is a direct band-gap semiconductor with an optical bandgap of 2.0 eV at AB-stacking arrangement, however, an optical band gap of less than 1. showed that CTFs can be synthesized through an organic synthetic route using an acid catalyst. 49 In these reports, semiconducting properties of CTFs are investigated by UVvis spectroscopy and photoluminescence properties.…”