27 Nov
2017
27 Nov
'17
11:06 a.m.
Please post and forward to your groups.
Center for Excitonics Seminar Series presents:
Exciting Metal-organic Frameworks: Electrons, Phonons, and Photons
November 28, 2017 at 4:30pm/rm: 34-401A
Aron Walsh
Department of Materials, Imperial College London
[http://www.rle.mit.edu/excitonics/wp-content/uploads/2017/10/1Walsh-Aron-27…]
Metal-organic frameworks (MOFs) are porous ordered arrays of inorganic clusters supported
by organic linking units. They have attracted attention for gas storage, separation and
catalysis, which rely on weak chemical bonding with an absorbate. The recent focus has
shifted to physical responses, with examples of magnetic, optical, ferroelectric, and
photovoltaic compounds. I will discuss progress in the understanding of how hybrid
frameworks interact with charge, heat, and light.
The optical response of MOFs can be tuned by chemical modification of the organic and
inorganic building blocks[1]. The control of electrical conductivity and redox activity in
MOF thin-films is opening a new dimension of applications[2,3]. The combination of
chemical diversity, mechanical flexibility, and electronic control in a single family of
compounds could enable metal-organic frameworks to become the semiconductors of the
future.
Beyond porous frameworks, I will also discuss progress in the understanding of
organic-inorganic halide perovskites, such as methylammonium lead iodide, which have
attracted significant attention for solar energy conversion. These compounds have been
termed ‘plastic crystals’ owing to the rotational-vibrational activity of the molecular
components, as well as the large anharmonic thermal displacements of the inorganic
framework. We have been developing models to describe the temporal behaviour of hybrid
perovskites that have been validated through a combination of quasi-elastic neutron
scattering, time-resolved vibrational spectroscopy, and inelastic X-ray scattering. There
remains significant challenges relating to the fundamental chemistry and physics of this
growing family of hybrid compounds.
This research has been supported by the Royal Society and the European Research Council,
with a wide collaboration network including simulations by Drs. Katrine Svane, Jarvist
Frost, and Jonathan Skelton.
1. “Chemical principles for electroactive metal–organic frameworks” MRS Bulletin 41, 870
(2016)
2. “Metallic conductivity in a two-dimensional cobalt dithiolene metal−organic
framework” J. Am. Chem. Soc. 139, 10863 (2017)
3. “Is iron unique in promoting electrical conductivity in MOFs?” Chemical Science 8, 4450
(2017)
4. “Atomistic origins of high-performance in hybrid halide perovskite solar cellsâ€
Nano Lett., 14, 2584 (2014)
5. “Direct observation of dynamic symmetry breaking above room temperature in
methylammonium lead iodide perovskite” ACS Energy Lett. 1, 880 (2016)
Aron Walsh is a Royal Society University Research Fellow and Full Professor in the
Department of Materials. Aron joined Imperial College London in October 2016. He was
awarded his PhD in Chemistry from Trinity College Dublin. He then worked for the US
Department of Energy at the National Renewable Energy Laboratory (NREL), followed by a
Marie Curie Fellowship hosted at University College London, and a European Research
Council Fellowship held at the University of Bath. His research involves cutting-edge
materials theory and similation applied to problems across solid state chemistry and
physics, including materials for solar cells and solar fuels, information storage,
batteries, thermoelectrics and solid-state lighting. He has a particular expertise in the
theory of semiconductors and dielectrics, and is developing innovative solutions for
materials data, informatics and design.
The Center For Excitonics Is An Energy Frontier Research Center Funded By The U.S.
Department Of Energy,
Office Of Science And Office Of Basic Energy Sciences
LIGHT REFRESHMENTS WILL BE SERVED!
