Synthesis of Two-Dimensional Zeolite-Templated Carbons with Ordered Micropores

Abstract

Zeolite-templated carbons (ZTCs) are a unique class of carbon materials characterized by ordered microporous structures, large surface areas, and substantial micropore volumes. ZTCs are synthesized by replicating the microporous structures of zeolite templates with carbon. Typically, zeolites with three-dimensional (3D) micropore connectivity have been used as templates for carbon deposition, producing ZTCs with 3D microporous channels and framework structures. In this study, we extend the synthesis of ZTCs using zeolite templates with two-dimensional (2D) micropore connectivity, which enables the production of 2D ZTCs—carbon nanosheets with vertically aligned ordered micropores. By studying 2D zeolites with various structures (UTL, IWV, MWW, and FER) and chemical compositions as templates, we identified key factors that govern the faithful replication of zeolite micropores with a carbon framework. Zeolite structures with large micropore apertures (≥12-membered rings), such as UTL and IWV, and a high density of acid sites (B or Al) were found to be beneficial for accurate carbon replication. The use of NaOH aqueous solution for template etching proved more effective in producing high-quality 2D ZTCs without inorganic residue, compared to the conventionally used HCl/HF aqueous solutions. Negative surface charges generated at carbon surfaces in highly alkaline NaOH solutions inhibited rapid stacking of carbon nanosheets via π-π interaction, which can cause the trapping of inorganic residues. We believe that the resulting 2D ZTCs hold significant promise for the fabrication of advanced membranes and energy storage devices.