Preparation of a Highly Porous Carbon Nitride by a Facile Post-Synthetic Method

Graphite-like carbon nitride (g-C3N4) is a potential material for use as photocatalysts, catalyst supports, electrodes, and so force. g-C3N4 is easily made from cheap CN compounds like melamine by pyrolysis. However, it was... [ view full abstract ]

Graphite-like carbon nitride (g-C3N4) is a potential material for use as photocatalysts, catalyst supports, electrodes, and so force. g-C3N4 is easily made from cheap CN compounds like melamine by pyrolysis. However, it was hard to prepare C3N4 materials with a large surface area. We found a facile method for the preparation of highly porous carbon nitride[1]. Our porous carbon nitride labelled as “nanoC3N4” works as a suitable photocatalyst support[2]. In this presentation, we report the effect of each step for the preparation of nanoC3N4 on its porosity and the structural analysis of nanoC3N4. We prepared nanoC3N4 in the following three steps. Step 1: Treating g-C3N4 with concd H2SO4 and washing it with water completely. Step 2: Treating it with aqueous NaOH solution and washing it with water completely. Step 3: Soaking it with EtOH twice. The obtained carbon nitride materials were finally dried in vacuo at 120 ˚C. We changed conditions for each step and measured the BET surface area and DH pore volume. The results are shown in the attached table. NanoC3N4 has more than 20 times a BET surface area than conventional g-C3N4 (Entry 5). In this preparation, the treatments with H2SO4 in Step 1 and EtOH in Step 3 are essential for preparing nanoC3N4. We analysed the structure of the nanoC3N4 by 13C solid-state MAS NMR, IR, XRD, and so force. We found that the polymeric structure of g-C3N4 was maintained even after the treatment with H2SO4. However, a graphite-like layered structure of g-C3N4 is exfoliated. Therefore, we estimate that Step 1 is necessary to exfoliate the polymeric CN layers, and Step 3 is needed to remove water molecules which connect polymeric CN compounds by hydrogen bonds. [1] T. Iwamoto, Y. Masui, J.-C. Wang, M. Onaka Chem. Lett. 2013, 42, 247. [2] K. Mori, T. Itoh, H. Kakudo, T. Iwamoto, Y. Masui, M. Onaka, H. Yamashita Phys. Chem. Chem. Phys. 2015, 17, 24086.