Water-based synthesis of nanoscale hierarchical metal-organic frameworks: Boosting adsorption and catalytic performance

Abstract

The combination of nano sizes, large pore sizes and green synthesis is recognized as one of the most crucial and challenging problems in constructing metal-organic frameworks (MOFs). Herein, a water-based strategy is proposed for the synthesis of nanoscale hierarchical MOFs (NH-MOFs) with high crystallinity and excellent stability. This approach allows the morphology and porosity of MOFs to be fine tuned, thereby enabling the nanoscale crystal generation and a well-defined hierarchical system. The aqueous solution facilitates rapid nucleation kinetics, and the introduced modulator acts as a deprotonation agent to accelerate the deprotonation of the organic ligand as well as a structure-directing agent (SDA) to guide the formation of hierarchical networks. The as-synthesized NH-MOFs (NH-ZIF-67) were assessed as efficient adsorbents and heterogeneous catalysts to facilitate the diffusion of guest molecules, outperforming the parent microZIF-67. This study focuses on understanding the NH-MOF growth rules, which could allow tailor-designing NH-MOFs for various functions.