Facile synthesis conditions, abundant hierarchical porosity, and high space–time yields (STYs) are prerequisites for the commercial application of zeolitic imidazolate frameworks (ZIFs). However, these prerequisites are rarely achieved simultaneously. Herein, a green and versatile strategy to rapidly synthesize hierarchically porous ZIFs (HP-ZIFs) was developed using an alkali as a deprotonating agent. The synthesis conditions were room temperature and ambient pressure in an aqueous solution, and the synthesis time could be reduced to 1 min. The produced HP-ZIFs had hierarchically porous structures with mesopores and macropores interconnected with micropores. The STY for HP-ZIFs was up to 9670 kg m⁻³ d⁻¹, at least 712 times the previously reported values. In addition, the porosity and morphology of the produced HP-ZIFs could be fine-tuned by controlling the synthesis parameters (e.g., reaction time, molar ratios, metal source, and alkali source). Compared with conventional ZIFs, the adsorption performance of the as-synthesized HP-ZIFs for p-xylene and n-hexane was significantly improved. Positron annihilation lifetime spectroscopy (PALS) was utilized to study the pore properties, and the adsorption behavior of HP-ZIFs on guest molecules was investigated using density functional theory (DFT) simulations. This strategy shows significant promise for the large-scale industrial production of desirable HP-ZIFs for adsorption applications.

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.

Nanoscale hierarchically porous metal–organic frameworks (NHP-MOFs) have received unprecedented attention in many fields owing to their integration of the strengths of nanoscale size (< 1 ​μm) and hierarchical porous structure (micro-, meso- and/or macro-pores) of MOFs. This review focuses on recent advances in the main synthetic strategies for NHP-MOFs based on different metal ions (e.g., Cu, Fe, Co, Zn, Al, Zr, and Cr), including the template method, composite technology, post-synthetic modification, in situ growth and the grind method. In addition, the mechanisms of synthesis, regulation techniques and the advantages and disadvantages of various methods are discussed. Finally, the challenges and prospects of the commercialisation of promising NHP-MOFs are also presented. The purpose of this review is to provide a road map for future design and development of NHP-MOFs for practical application.