Nanostructured morphology control and phase transition of zeolitic imidazolate frameworks as ultra-high performance adsorbent for water purification
Designing the materials targeting heavy metal ions with fast and high effective adsorption performance is imperative for heavy metal contaminants removal from water ecosystems. Inspired by the “function follows form” principle, we herein develop an approach to control over the morphologies and phases of Zeolitic Imidazolate Framework-based nanomaterials (denoted as ZIF-8-x, x presents the ratio of methanol/water) for seeking ultra-high heavy metal adsorption property. By tuning solution conditions, the transformation of various obtained nanocrystals involved the morphologies from typical rhombic dodecahedron to leaf shape, accompanied with the phase transition from ZIF-8 to ZIF-L phase and amorphous regions increased, benefit to the adsorption interaction between heavy metal ions and 2-methylimidazole binding sites for enhancing adsorption capacities. The optimized ZIF-8-x of ZIF-8-0 (synthesized in pure water) with leaf-like morphology and ZIF-L phase endows the prepared adsorbent with extra imino groups for heavy metal ions adsorption, which exhibits the highest adsorption capacity towards Cu(II) (~1457.87 mg g-1) and quickly get adsorption equilibrium in 5 min. Our results suggest that the enhanced adsorbents can be developed by engineering the morphology and phase of nanocrystals and the as-prepared ZIF-8-0 can be a promising candidate for water purification.