News

New MSci project students!

This month we are joined by Matthew Liddle and Samuel Gale, who will be carrying out their Masters research projects with the group. Matt’s project is looking at phase behaviour of a carboxyphosphonate MOF, BIRM-1, which has potential use in ion exchange and transport. Sam’s project is investigating relationships between the physical properties of hybrid perovskite ferroelectrics and their structural chemistry.

Both Sam and Matt also have a second co-supervisor, Prof Paul Anderson, as well as his PhD student Joe Barker, who joins us as an honorary group member involved in day-to-day supervision of the projects.

Welcome, Sam, Matt and Joe!

MSci project hand-in

Congratulations to Vicky and Matt for handing in their MSci theses today!

The group celebrated the occasion with a wonderfully al-fresco lunch and bubbly at Joe’s bar. Much like today’s weather, the projects this year were not exactly free from disruption but Vicky and Matt both did a great job nevertheless!

It was great to have you in the group – good luck for all your future endeavours and well done again!

Origins of Ferroelectricity

Congratulations to former Masters student Dom Allen, whose work on ferroelectricity in MDABCO-based perovskites has just been published in the Journal of Materials Chemistry C!

MDABCO perovskites (MDABCO = N-methyl-1,4-diazoniabicyclo[2.2.2]octane) are one of a new class of ferroelectric materials, which have properties that rival best-in-class materials such as barium titanate or lead zirconate titanate. Ferroelectrics have a wide range of hugely important applications as capacitors and memory storage (e.g., in smartphones and computers), sensors, actuators and non-linear optics.

Dom’s modelling showed that the key ingredients that drive spontaneous polarisation in [MDABCO][NH4][I3] and related structures are (i) alignment of the A-site cation along <111> directions, (ii) ever-present dipolar coupling, and (iii) strain coupling between neighbouring sites. Contrary to prevailing wisdom, he found that hydrogen bonding, whilst it may still be important in determining the magnitude of polarisation or transition temperature, is actually not essential to drive this phenomenon.

The paper, which was invited for cover art, is Open Access and can be read here.

Dom’s work was supplemented by first-principles calculations from Nick Bristowe and his co-supervisor at Oxford was Andrew Goodwin. Well done all!

Tunable core–shell MOF nanoparticles

We are delighted that Kieran’s paper based on his MChem Part II research project in Oxford has now been published in Chemical Science!

The article describes how, by shortening the length of reaction, Zn/Cd-based ZIF-8 nanoparticles form with a Cd-rich core and Zn-rich shell. We collaborated with Sean Collins, whose beautiful scanning transmission electron microscopy showed us the core–shell structures, which we then used as the basis for a new model, first suggested by Andrew Goodwin to fit high-resolution X-ray diffraction data. This model allowed Kieran to quantify for numerous bulk samples the amount of Cd-rich material and Zn-rich material in the particles, as well as where the core–shell interface lay and how diffuse it was. He performed 99 syntheses at a range of temperatures and Zn/Cd ratios to map out how the nanoparticles’ internal interface and structure varied as a function of reaction conditions. Finally, we showed using in situ X-ray diffraction that the particles form first with a Cd-rich core followed by Zn-rich shell and the interface becomes increasingly diffuse the longer the reaction goes on.

By developing this simple synthesis and powerful new analysis method, and understanding the underlying formation mechanism, we have shown that it is indeed possible to control the spatial distribution of different components in metal–organic frameworks (MOFs) such as ZIF-8, which is really important to enable researchers to tap into their enormous potential as gas storage, separations and catalysis materials.

See the citation and all our publications here.

This work could not have been performed without several amazing co-authors: thank you Sean Collins for the STEM–EDS, Andrew Goodwin for co-supervision, Emily Reynolds (now at ISIS), Frank Nightingale, Hanna Boström (now at the Max Planck Institute for Solid State Research, Germany) and Simon Cassidy in the Goodwin group for help with all aspects of the XRD, Daniel Dawson and Sharon Ashbrook for NMR insights, Oxana Magdysyuk at Diamond beamline I12 for help with the in-situ beamtime, and Paul Midgley at Cambridge for support with the microscopy – Well done and thank you!