Yin Congcong, Zhang Zhe, Zhou Jiemei, Wang Yong
State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemical Engineering, Nanjing Tech University, Nanjing 211816, P. R. China.
ACS Appl Mater Interfaces. 2020 Apr 22;12(16):18944-18951. doi: 10.1021/acsami.0c03246. Epub 2020 Apr 10.
Covalent triazine framework (CTF) nanosheets featured with uniform intrinsic nanoporosity and excellent stability are promising building blocks for fast, selective membranes. However, it remains challenging to produce ultrathin CTF nanosheets, significantly hindering the development of CTF-based membranes. Herein, we develop a mild oxidation strategy to exfoliate CTFs, enabling the preparation of highly permeable membranes with stacked CTF nanosheets as the selective layers. The interlamellar spacing of CTF is effectively expanded following the mechanism of "proton donating-accepting" in which dimethyl sulfoxide (DMSO) works as a soft oxidant, leading to ultrathin CTF nanosheets with the assistance of ultrasonication. Furthermore, oxygen-containing functional groups are also introduced onto the CTF nanosheets through mild oxidation, improving surface hydrophilicity. The CTF nanosheet can be stacked onto porous substrates by vacuum filtration to form composite membranes with the thickness of the stacked CTF nanosheets down to ∼30 nm. Thus-obtained membranes exhibit impressive dye separation performances with both high water permeance and high rejection. This work provides not only an efficient method to synthesize ultrathin CTF nanosheets but also a process to prepare fast but selective membranes for molecular separations.
具有均匀固有纳米孔隙率和出色稳定性的共价三嗪框架（CTF）纳米片是用于制备快速、选择性膜的理想构建单元。然而，制备超薄CTF纳米片仍然具有挑战性，这严重阻碍了基于CTF的膜的发展。在此，我们开发了一种温和氧化策略来剥离CTF，从而能够制备以堆叠的CTF纳米片作为选择性层的高渗透性膜。CTF的层间距通过“质子供体-受体”机制有效地扩大，其中二甲基亚砜（DMSO）作为软氧化剂，在超声作用下形成超薄CTF纳米片。此外，通过温和氧化还将含氧官能团引入到CTF纳米片上，提高了表面亲水性。CTF纳米片可以通过真空过滤堆叠在多孔基材上，形成复合膜，堆叠的CTF纳米片厚度低至约30nm。由此获得的膜表现出令人印象深刻的染料分离性能，具有高透水率和高截留率。这项工作不仅提供了一种合成超薄CTF纳米片的有效方法，还提供了一种制备用于分子分离的快速且选择性膜的工艺。
