Macro-Meso-Microporous Metal-Organic Frameworks: Template-Assisted Spray Drying Synthesis and Enhanced Catalysis

Area of Science:

• Materials Science
• Nanotechnology
• Chemical Engineering

Background:

• Hierarchically porous metal-organic frameworks (HP-MOFs) offer enhanced performance due to multiple pore sizes.
• Previous HP-MOFs typically exhibit only two types of pores.
• Developing HP-MOFs with macro-meso-micropores is crucial for advanced applications.

Purpose of the Study:

• To propose an efficient strategy for fabricating HP-MOFs with macro-meso-micropores.
• To demonstrate the fabrication of HP-ZIF-8 and HP-HKUST-1 using the proposed method.
• To investigate the catalytic properties of the synthesized HP-ZIF-8.

Main Methods:

• Template-assisted spray drying using polystyrene (PS) nanoparticles.
• Etching process to remove PS templates and generate macropores.
• Fabrication of nanosized ZIF-8 (N-ZIF-8) as building blocks.

Main Results:

• Successfully synthesized HP-MOFs with macropores, mesopores, and intrinsic micropores.
• Demonstrated tunability of macropore and mesopore structures by controlling template size and N-ZIF-8 size.
• HP-ZIF-8 exhibited superior catalytic activity and conversion in the Knoevenagel reaction compared to conventional ZIF-8.
• HP-ZIF-8 showed improved recyclability over N-ZIF-8.

Conclusions:

• The proposed method provides an efficient route to construct HP-MOFs with three distinct pore hierarchies.
• HP-ZIF-8 shows significant potential as a catalyst due to its unique hierarchical pore structure.
• The strategy is extendable to other MOF materials like HP-HKUST-1.