Zeolitic imidazolate framework-8 nanosheet assemblies for high-efficiency small molecule adsorption

Metal-organic frameworks (MOFs) have gained tremendous attention based on the prospect of application-oriented structural tuning. In this study, the surfactant (SDS)-directed hydrothermal synthesis route was adopted for a one-pot, bottom-up synthesis of ZIF-8 spherical assemblies, stacked with externally oriented and intergrown two-dimensional (2D) nanosheets. The as-obtained nanosheet assemblies exhibited good crystallinity, a large surface area, and excellent thermal stability, as shown by XRD, BET, and TGA, respectively. More importantly, the ZIF-8 nanosheet assemblies displayed excellent small molecule adsorption characteristics, especially for the negatively charged dyes, including rose bengal (RB), uni-blue A (UA), and methyl orange (MO). Furthermore, samples showed a pseudo-second-order adsorption mechanism for dye molecules and presented a good fit for Langmuir's and Temkin's adsorption isotherms with an R² value of 0.98 and 0.94, respectively. Adsorbent–adsorbate electrostatic interaction, nanosheet structures, molecular size and structural aromaticity of the dye, and the presence of SDS functionalities were found as the essential components for the high-capacity dye adsorption as compared with previous studies.