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Control of metal-organic framework crystallization by metastable intermediate pre-equilibrium species

DOI: 10.1002/anie.201810039 DOI Help

Authors: Hamish Yeung (University of Oxford) , Adam F. Sapnik (University of Oxford) , Felicity Massingberd-mundy (University of Oxford) , Michael W. Gaultois (University of Liverpool) , Yue Wu (National University of Singapore) , Duncan X. Fraser (University of Oxford) , Sebastian Henke (Technische Universität Dortmund) , Roman Pallach (Technische Universität Dortmund) , Niclas Heidenreich (Christian-Albrechts-Universität zu Kiel) , Oxana Magdysyuk (Christian-Albrechts-Universität zu Kiel) , Nghia T. Vo (Diamond Light Source) , Andrew L. Goodwin (University of Oxford)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Angewandte Chemie International Edition

State: Published (Approved)
Published: November 2018
Diamond Proposal Number(s): 16354 , 16450

Abstract: 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 Zn‐imidazolate species, thus accelerating or inhibiting crystallization, respectively. We thereby find that concentration can be effectively used as a synthetic handle to directly control particle size, with great implications for industrial scale‐up and gas sorption applications. These finding enables us to rationalise the apparent contradictions between previous studies of ZIF‐8 and, importantly, opens up new opportunities for the control of crystallization in network solids more generally, from the design of local structure to assembly of particles with precise dimensions.

Journal Keywords: Metal-Organic Frameworks; crystal engineering; nanoparticles; Reactive intermediates; Kinetics

Subject Areas: Chemistry

Instruments: I12-JEEP: Joint Engineering, Environmental and Processing