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!

Monitoring MOFs

Ever wanted to monitor your MOF synthesis on the cheap? Look no further, because Felicity’s Open Access paper describing how MOF scale-up can be improved using an open source, multi-channel monitor – all built for less than $100 – is now out in Scientific Reports! She used simultaneous temperature, turbidity, pH, and visible light absorbance to track the formation of STA-16(Ni), observing the reaction critical processes that guided the development of a faster and more efficient synthesis route to material with comparable porosity.

The work was performed while Felicity was a Part II student in Oxford during her project at Johnson Matthey, co-supervised by Tim Johnson, Stephen Poulson and Stephen Bennett.

New year, new arrivals

This month we are joined by Harry Lloyd and Aaron Chambers, who will be starting two exciting, collaborative PhD projects in the group!

Harry is studying time-resolved dynamics of framework materials under electric fields on a joint Diamond Light Source PhD studentship. He’ll be co-supervised by Dr Lucy Saunders and Dr Mark Warren from Diamond, where he’ll spend two years getting hands-on at Beamline I19-1!

Aaron is studying the formation and processing of MOF nanoparticle composites as part of a collaboration initiative between the University of Birmingham and BAM, the Federal Institute for Materials Research and Testing, Berlin. He’ll be co-supervised by Dr Brian Pauw from BAM, where he’ll visit to perform 3-D printing and in-depth structural characterisation.