Dr. Petra Ágota Szilágyi, Department of Pharmaceutical, Chemical & Environmental Sciences, University of Greenwich

Metal-Organic Frameworks - Templates and Supports of Pd Particles

Metal-organic frameworks (MOFs) have high and regular porosity, and topological and chemical tuneability. They are therefore promising materials for supporting nano-objects. [1-4]

The present work is aimed at the assessment of MOFs as templates for the synthesis and support of nanoclusters, i.e. particles < 1 nm, as a function of pore geometry and chemical functionality.

Selected MOFs (MIL-101, NH₂-MIL-101, UiO-66, NH₂-UiO-66, etc.) were synthesised by solvothermal methods and guest precursors were infused from appropriate solution. Palladium particles (nanoparticles, nanoclusters and single atoms) were obtained by precursor reduction in H₂ stream at elevated temperatures.

MOF integrity verified by PXRD and the measurement of the BET surface areas before and after loading. Nanocluster morphology was characterised by HAADF-STEM, their oxidation state was checked XPS and their crystalline phase was established by Pair Distribution Function (PDF) and EXAFS analyses. Density Functional Theory (DFT) was used to model the systems.

No MOF was found to decompose during loading. Nanoclusters were found to form large particles on the surfaces of some pristine MOFs but were embedded in the pores of functionalised MOFs. In the case of functionalised MOFs the surface chemistry of nanoclusters was found to be modified.

The results show that not only the pore structure but also the chemical composition of MOFs’ pores has an impact on the abilities of MOFs to support transition-metal nanoclusters, as also supported by DFT calculations. [5,6] Furthermore, the chemical functionalities of the frameworks influence the surface chemistry and potentially the crystal lattice of the nanoclusters, as revealed by our XPS, PDF and EXAFS results.

Such insight creates understanding in the mechanism and promotes rational design of nanocatalysts for particular applications. 

1. Chem. Soc. Rev. 2013:1807
2. Eur. J. Inorg. Chem. 2010:3701
3. CrystEngComm. 2015:199
4. J. Mater. Chem. 2012:10102
5. Chem. Commun. 2016:5175
6. J. Mater. Chem. A, 2017, DOI: 10.1039/C7TA03134C

Short Bio

Dr Petra Ágota Szilágyi is a Senior Lecturer in Materials Chemistry at the University of Greenwich. Dr Szilágyi received PhD degrees in Chemistry and in Physics/Nanophysics in 2008 and has worked in Hungary, France, the Netherlands and Australia.

Dr Szilágyi has had a successful early research career with over 30 international peer-reviewed publications and international patents. She has internationally recognised experience and expertise in the use of metal-organic frameworks for energy applications. ^{[J. Mater. Chem. A, 10.1039/C7TA03134C; Chem. Sci. 2016:666; Chem. Commun. 2016:5175; Phys. Chem. Chem. Phys. 2014:5803; Chem. Mater. 2008:6721]} Her current research interest is focussed on the development of porous materials as synthetic templates and supporting scaffolds for geometry- and surface-chemistry controlled nanoparticles for energy conversion and storage.

Host: Professor Torben René Jensen, Department of Chemistry