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.

Pre-equilibrium species in MOF crystallization

We’re very pleased to announce our paper on the crystallization of ZIF-8 has just been accepted! It’s been a challenging piece of work, not least because it all began when we made the surprising observation that crystallization got SLOWER when we increased the concentration of our reactants…

There is an increasingly large amount of interest in metal-organic frameworks (MOFs) for a variety of applications, from gas sensing and separations to electronics and catalysis. Their exciting properties arise from their modular architectures, which self-assemble from different combinations of metal-based and organic building units. However, the exact mechanisms by which they crystallize remain poorly understood, thus limiting any realisation of real “structure by design”. We report important new insight into MOF formation, gained using in situ X-ray diffraction, pH and turbidity measurements to uncover for the first time the evolution of metastable intermediate species in the canonical zeolitic imidazolate framework system, ZIF-8. We reveal that the intermediate species exist in a dynamic pre-equilibrium prior to network assembly and, depending on the reactant concentrations and the progress of reaction, the pre-equilibrium can be made to favour under- or over-coordinated species, thus accelerating or inhibiting crystallization, respectively. We thereby find that concentration can be effectively used as a synthetic handle to control particle size, with great implications for industrial scale-up and gas sorption applications. This finding enables us to rationalise the apparent contradictions between previous studies and, importantly, opens up new opportunities for the control of crystallization of network solids more generally, from the design of local structure to assembly of particles with precise dimensions.

The paper is published with Angewandte Chemie, International Edition and can be found here. A previous version can also be downloaded for free on ChemRxiv.

Many thanks to all co-authors, Diamond for beamtime, SCG Innovation for funding and everyone else that helped out along the way!

Summer project on MOF formation 2018

We have guaranteed funding for at least one 6-8 week summer project in 2018 here in Oxford and the possibility to apply for more! Prospective students should be a current undergraduate in Chemistry or a related discipline and show interest in one or more of these topics: chemical kinetics, crystallisation, metal-organic frameworks, X-ray diffraction and in-situ measurements. Deadlines for other funding sources occur early in 2018 so please contact Hamish if interested.