Applications of Light
Harvesting MOFs
Brittney Williams
CHEM 435
February 6, 2019
What is a MOF?
• First discovered in the 1990s
• Crystalline hybrid materials
created from organic and
inorganic materials via selfassembly
• Diverse chemical and
structural makeups
• Professor Omar Yaghi of UC
Berkeley pioneered research
in the field
•
Published the first report of a MOF in
1999
Ability to
study short
and long
range energy
transfer
Benefits of
Using MOFs
Porous
structure
facilitates
diffusion
Integrate light
harvesting
and catalytic
components
into one
platform
Simplifies mathematical
simulation
Incorporation of catalytic
active centers into metal
nodes or bridging ligands
Enables conversion of solar
energy to chemical energy
Models for Energy Transfer
• Förster and Dexter energy transfer
mechanisms
• Weak coupling limit
• Förster model
• Presumes only dipole-dipole term of
Coulomb interaction important
Förster rate
• “Exchange” term
• Dexter model
Dexter rate
Energy
Transfer
within MOFs
Organic ligands serve as
antenna to sensitize lanthanide
metal nodes
Efficient energy transfer
• 2009 Loh and coworkers
• 2013 Hupp and coworkers
Timeline of artificial photosynthesis
1972
2012
2014
Fujishima and Honda report first
example of artificial photosynthesis
Fu and coworkers find that aminefunctionalized Ti-centered MOFs
enhances catalytic activity for CO2
reduction
Sun and coworkers found that Pt
doping on the compound reported
by Fu can have increased formate
production
First published report of a MOF by
Omar Yaghi
Liu and coworkers grew a framework
with nanorods for CO2
photoreduction catalyst
1999
2013
MOFs for
Artificial
Photocatalysis
Photocatalytic Oxidative
Degradation of Organic Molecules
• 2007: Garcia and coworkers reported oxidative degradation
with MOF-5 under UV light
• 2014: Zhang and coworkers found that a Titanium (IV) based
MOF is reported to be an active photocatalyst for dye
degradation
• Little effort has been put into studies of the kinetics or
mechanisms of the systems
• 2012: Li and coworkers performed kinetics tests
•
Terephthalic acid as a probe molecule
• No photoluminescence found in the absence of the
MOFs
Organic Photocatalysis
• 2011: Lin and coworkers incorporated metal
organic dyes into UiO-type MOFs and were able to
obtain solid state photocatalysis
• 2011: Wu and coworkers reported a tin-porphoryn
MOF as a photocatalyst for oxidation of sulfides to
sulfoxides
• 2012: Duan and coworkers reported a pair of MOF
enantiomers as asymmetric photocatalysts
Photocatalytic Hydrogen
Evolution and CO2 Reduction
• One of the most promising scenarios for solar energy conversion
• MOFs exhibit similar photocatalytic activities to semiconductors
• 2010: Garcia and coworkers tested a simple UiO-66 MOF and found
it possessed catalytic activity for hydrogen evolution
• 2012: Li and coworkers reported photocatalytic CO2 reduction
catalyzed by a Ti based MOF
• Although photo-mediated reactions can be achieved, the activities
are very low and most of the systems are not catalytic due to a
turnover number below 1
Water Oxidation
• Few people have researched the other
half reaction of water splitting
• 2011: Lin and coworkers are the first to
use MOF as a water oxidation catalyst
• 2012: Lin and coworkers prepared
catalytically active MOFs with larger
channels using a longer Ir-based
bridging ligand
• 2013: Das and coworkers incorporated a
molecular water oxidation catalyst into
the MIL-101(Cr) framework
What’s Next?
The future of light harvesting MOFs
Spectral overlap of the absorption features of
MOFs with that of the solar spectrum need to
be improved
Challenges
that Need to
be Overcome
Recognize that exciton transport is usually
diffusive and transport differences need to be
boosted
Cascades for charge transport
Incorporate MOFs into devices for their
application
Questions?
References
• Zhang, T.; Lin, W. Metal–Organic Frameworks for Artificial Photosynthesis and Photocatalysis.
Chem. Soc. Rev. 2014, 43 (16), 5982–5993.
• Frost, S. MATERIAL OF THE MONTH: METAL ORGANIC FRAMEWORKS. metal organic frameworks
4.
• J. Gao, J. Miao, P.-Z. Li, W. Y. Teng, L. Yang, Y. Zhao, B. Liu and Q. Zhang, Chem. Commun., 2014, 50,
3786–3788.
• Wang, J.-L.; Wang, C.; Lin, W. Metal–Organic Frameworks for Light Harvesting and Photocatalysis.
ACS Catalysis 2012, 2 (12), 2630–2640.
• Gomes Silva, C.; Luz, I.; Llabrés i Xamena, F. X.; Corma, A.; García, H. Water Stable Zr–
Benzenedicarboxylate Metal–Organic Frameworks as Photocatalysts for Hydrogen Generation.
Chemistry – A European Journal 2010, 16 (36), 11133–11138.
• Nepal, B.; Das, S. Sustained Water Oxidation by a Catalyst Cage-Isolated in a Metal–Organic
Framework. Angewandte Chemie International Edition 2013, 52 (28), 7224–7227.
• So, M. C.; Wiederrecht, G. P.; Mondloch, J. E.; Hupp, J. T.; Farha, O. K. Metal–Organic Framework
Materials for Light-Harvesting and Energy Transfer. Chemical Communications 2015, 51 (17),
3501–3510.