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.