Microwave induced "egg yolk" structure in Cr/V-MIL-53

Area of Science:

• Materials Science
• Chemistry
• Nanotechnology

Background:

• Metal-organic frameworks (MOFs) are porous materials with tunable properties.
• Mixed-metal MOFs offer enhanced functionality compared to single-metal counterparts.
• Controlling MOF morphology, such as core-shell structures, is crucial for targeted applications.

Purpose of the Study:

• To synthesize mixed-metal "egg yolk" MOFs using a one-pot microwave procedure.
• To investigate the structural differences between microwave-assisted and solvothermally synthesized MOFs.
• To study the impact of chromium (Cr) and vanadium (V) incorporation on MOF flexibility and CO2 adsorption.

Main Methods:

• One-pot microwave-assisted synthesis of (Cr/V)-MIL-53 core and Cr-MIL-53 shell MOFs.
• Solvothermal synthesis for comparison, yielding homogeneous mixed-metal MOFs.
• Temperature-dependent X-ray powder diffraction (T-XRPD) for structural analysis.
• CO2 adsorption measurements to evaluate gas uptake and interaction.

Main Results:

• Successfully synthesized core-shell "egg yolk" MOFs via microwave irradiation.
• Observed distinct structural and property differences between microwave and solvothermal methods.
• Demonstrated that Cr and V significantly influence the flexibility and "breathing" behavior of MIL-53 MOFs.
• Quantified the effect of these structural modifications on CO2 adsorption capacity.

Conclusions:

• Microwave synthesis provides a facile route to hierarchical mixed-metal MOFs with "egg yolk" morphology.
• The presence and distribution of Cr and V in MIL-53 MOFs critically affect their dynamic structural responses.
• These findings offer insights into designing advanced MOFs for selective gas adsorption and separation applications.