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A Technical Guide for Performing Spectroscopic Measurements on Metal-Organic Frameworks
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Rapid Exciton Transport and Structural Defects in Individual Porphyrinic Metal Organic Framework Microcrystals
Sajia Afrin1,2, Xiaozhou Yang3, Amanda J Morris3
1Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States.
Journal of the American Chemical Society
|February 8, 2024
Summary
Single-crystal microscopy reveals how structural defects impact the photochemical properties of porphyrin-based metal-organic frameworks (MOFs). This study highlights ultrafast dynamics and exciton transport within PCN-222 MOF crystals.
Area of Science:
- Materials Science
- Photochemistry
- Spectroscopy
Background:
- Porphyrin-based metal-organic frameworks (MOFs) are promising photochemical platforms.
- Current characterization relies on ensemble techniques, averaging functional properties.
- Single-crystal analysis is needed to understand heterogeneity.
Purpose of the Study:
- To investigate ultrafast dynamics in PCN-222 MOF single crystals using time-resolved pump-probe microscopy.
- To correlate spectroscopic observables with inter- and intracrystal structural heterogeneity.
- To elucidate the role of structural defects in MOF photochemical functionality.
Main Methods:
- Time-resolved pump-probe microscopy on PCN-222 MOF single crystals.
- Simultaneous high spatial and temporal resolution for correlating dynamics with structure.
- Single-particle-resolved measurements of excited state lifetime, quantum yield, and transport.
Main Results:
- Significant variations in excited state lifetime observed between individual PCN-222 crystals.
- Excited state lifetime and photoluminescence quantum yield correlate with microscale structural defects within crystals.
- Rapid, subdiffusive exciton transport observed, slowing on the 10s of picoseconds timescale.
- Exciton diffusion coefficients range from 0.27 to 1.0 cm²/s within the first 200 ps.
Conclusions:
- Single-particle-resolved measurements provide unprecedented insight into MOF photochemistry.
- Structural defects significantly influence excited state dynamics and exciton transport in porphyrin-based MOFs.
- Understanding these relationships is crucial for optimizing MOF-based photochemical applications.
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