Core-Shell Zeolitic Imidazolate Frameworks for Enhanced Hydrogen Storage

Area of Science:

• Materials Science
• Nanotechnology
• Chemical Engineering

Background:

• Zeolitic imidazolate frameworks (ZIFs) are porous materials with potential applications in gas storage.
• Developing ZIFs with improved hydrogen storage capacity is crucial for clean energy solutions.
• Controlling the structure and composition of ZIFs can enhance their gas adsorption properties.

Purpose of the Study:

• To synthesize core-shell ZIF-8@ZIF-67 and ZIF-67@ZIF-8 structures using a seed-mediated approach.
• To investigate the hydrogen (H₂) and carbon dioxide (CO₂) storage capabilities of these core-shell ZIFs.
• To correlate the enhanced gas storage performance with the unique structural and elemental properties of the core-shell morphology.

Main Methods:

• Solvothermal synthesis utilizing a seed-mediated methodology.
• Characterization using Transmission Electron Microscopy-Energy-Dispersive X-ray Spectrometry (TEM-EDS), X-ray Photoelectron Spectroscopy (XPS), and Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES).
• Gas adsorption measurements at 77 K and 1 bar to determine H₂ storage capacity, with isotherm data fitted using the Langmuir model.

Main Results:

• Successful synthesis of core-shell ZIF-8@ZIF-67 and ZIF-67@ZIF-8 structures with a controlled Co/Zn elemental composition of approximately 0.50.
• Core-shell ZIFs exhibited significantly enhanced H₂ storage capacities (2.03 wt % for ZIF-8@ZIF-67 and 1.69 wt % for ZIF-67@ZIF-8), representing a 41% and 18% increase over ZIF-8, respectively.
• The core-shell ZIFs demonstrated superior H₂ storage compared to bimetallic ZIFs and physical mixtures, attributed to their unique porous confinement and elemental heterogeneity. Improved CO₂ capture behavior was also observed.

Conclusions:

• The rationally designed core-shell ZIFs possess unique structural features that lead to remarkably enhanced H₂ storage capacities.
• The controlled porosity and elemental heterogeneity in core-shell ZIFs are key factors for their superior gas storage performance.
• These findings highlight the high potential of core-shell ZIFs in hydrogen storage applications and suggest their utility in other gas separation and storage technologies.