Dual Zn source strategy for synthesizing ZIFs: zero discharge, less raw material, high output, and better adsorptive performance

Abstract

In this study, dual Zn source (DZS) strategy, using Zn(NO₃)₂ and Zn(OH)₂, to prepare ZIF-8 with high quality and high output. DZS strategy eliminated waste acid and improved the low yield of ZIF-8 with low imidazole ligand consumption, achieving a 84% ZIF-8 yield. This ZIF-8 has large surface area (1571 m² g⁻¹) with unique diamond dodecahedron morphology, showing excellent adsorption desulfurization ability (19 mg g⁻¹). DFT calculation showed that the introduction of Zn(OH)₂ or ZnO caused the diffusion of the LUMO orbital from the initial Zn to the entire imidazole ring and metal atoms. The diffusion resulted in an enhanced electron accepting ability of the intermediate reactants and accelerated the formation of ZIF-8 crystals. Most importantly, the resultant mother liquor is directly reused with zero-discharge in DZS method. Similarly, other ZIFs with different ligands, including MAF-6, ZIF-71, and ZIF-11, could be prepared by our method as well.