Lisowska Karolina, Purser Will, Chang Fuqiang, Suter Theo M, Miller Thomas S, Sella Andrea, Howard Christopher A, McMillan Paul F, Corà Furio, Clancy Adam J
Department of Chemistry, University College London,London WC1E 0AJ, UK.
Department of Chemical Engineering, University College London, London WC1E 7JE, UK.
Philos Trans A Math Phys Eng Sci. 2023 Oct 30;381(2259):20220339. doi: 10.1098/rsta.2022.0339. Epub 2023 Sep 11.
Crystalline two-dimensional carbon nitrides with polytriazine imide (PTI) structure are shown to act amphoterically, buffering both HCl and NaOH aqueous solutions, resulting in charged PTI layers that dissolve spontaneously in their aqueous media, particularly for the alkaline solutions. This provides a low energy, green route to their scalable solution processing. Protonation in acid is shown to occur at pyridinic nitrogens, stabilized by adjacent triazines, whereas deprotonation in base occurs primarily at basal plane NH bridges, although NH edge deprotonation is competitive. We conclude that mildly acidic or basic pHs are necessary to provide sufficient net charge on the nanosheets to promote dissolution, while avoiding high ion concentrations which screen the repulsion of like-charged PTI sheets in solution. This article is part of the theme issue 'Exploring the length scales, timescales and chemistry of challenging materials (Part 2)'.
具有聚三嗪酰亚胺（PTI）结构的结晶二维碳氮化物表现出两性作用，可缓冲盐酸和氢氧化钠水溶液，形成带电荷的PTI层，这些层会在其水介质中自发溶解，特别是在碱性溶液中。这为其可扩展的溶液加工提供了一条低能耗、绿色的途径。研究表明，在酸性条件下质子化发生在吡啶型氮原子上，并由相邻的三嗪稳定，而在碱性条件下脱质子主要发生在基面NH桥上，不过NH边缘脱质子也存在竞争。我们得出结论，需要适度的酸性或碱性pH值，以使纳米片上具有足够的净电荷来促进溶解，同时避免高离子浓度，因为高离子浓度会屏蔽溶液中带相同电荷的PTI片层之间的排斥力。本文是主题为“探索具有挑战性材料的长度尺度、时间尺度和化学性质（第2部分）”的一部分。
