Hierarchically Micro- and Mesoporous Zeolitic Imidazolate Frameworks Through Selective Ligand Removal

Area of Science:

• Materials Science
• Nanotechnology
• Chemical Engineering

Background:

• Zeolitic imidazolate frameworks (ZIFs) possess tunable porosity but often lack hierarchical pore structures.
• Hierarchical porosity is crucial for efficient mass transport in applications like adsorption and catalysis.

Purpose of the Study:

• To develop a new method for creating hierarchically porous ZIFs with controlled micro- and mesoporosity.
• To investigate the impact of ligand composition and thermal treatment on pore structure.
• To evaluate the performance of these materials in adsorbing organic dyes.

Main Methods:

• Synthesis of mixed-ligand ZIFs (ML-ZIFs) using 2-aminobenzimidazole (NH2-bIm) and 2-methylimidazole (2-mIm).
• Controlled thermal treatment to selectively remove NH2-bIm via ligand cleavage.
• Characterization of pore structure and evaluation of methylene blue adsorption capacity.

Main Results:

• Successful engineering of hierarchically porous ZIFs with dual micropore and mesopore systems.
• Demonstrated control over mesopore formation by adjusting ligand ratios and heating conditions.
• Achieved a 40-fold increase in methylene blue adsorption capacity in 10%NH2-ZIF-2h compared to ZIF-8.

Conclusions:

• The SeLiRe method provides a versatile route to design micro/mesoporous ZIFs.
• Hierarchically porous ZIFs exhibit enhanced performance in adsorbing organic dyes due to improved diffusion kinetics.
• This approach is promising for applications in liquid phase purification, catalysis, and sensing.