Metal-Organic Framework Optical Thermometer Based on Cr³⁺ Ion Luminescence

Area of Science:

• Materials Science
• Solid-State Chemistry
• Nanotechnology

Background:

• Perovskite-type metal-organic frameworks (MOFs) exhibit unique structural, optical, and phonon properties.
• Heterometallic MOFs offer tunable characteristics by incorporating multiple metal ions.

Purpose of the Study:

• To synthesize and characterize a series of heterometallic perovskite-type MOFs.
• To investigate the structural, optical, and luminescence properties of these novel materials.
• To explore their potential application as luminescence-based thermometers.

Main Methods:

• Synthesis of six heterometallic perovskite-type MOFs with varying Cr:Al ratios.
• Diffuse reflectance spectroscopy for crystal field strength (Dq/B) and energy band gap (Eg) determination.
• Raman spectroscopy, X-ray diffraction (XRD), and lifetime decay analysis for structural and compositional correlation.
• Temperature-dependent luminescence studies (80-400 K) for thermometer development.

Main Results:

• Established a series of MOFs with the formula [EA]2NaCrxAl1-x(HCOO)6.
• Determined Dq/B values in the range of 2.33-2.76, correlating with composition.
• Demonstrated a strong correlation between temperature, composition, and spectroscopic properties.
• Achieved the first luminescence thermometer based solely on Cr3+ luminescence in an organic-inorganic framework.

Conclusions:

• The synthesized heterometallic perovskite-type MOFs exhibit tunable spectroscopic properties.
• These MOFs show significant potential for noncontact thermometry applications.
• Compositional control is key to tailoring luminescence for specific sensing applications.