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DEFNET Report Summary

Project ID: 641887
Funded under: H2020-EU.1.3.1.

Periodic Reporting for period 1 - DEFNET (DEFect NETwork materials science and engineering)

Reporting period: 2015-01-01 to 2016-12-31

Summary of the context and overall objectives of the project

DEFNET (DEFect NETwork materials science and engineering) is the first integrated European Training Network (ETN) at the intersection of chemistry, physics and engineering dealing with the structural and functional complexity of molecular network materials such as Metal-organic Frameworks (MOFs), including Double Metal Cyanides (DMCs). It is a unique research and training platform for 15 early stage researchers (ESRs) mainly focusing on the DEFective NETwork materials based on MOFs and DMCs. The wide-ranging properties of MOFs arise in many cases mainly due to the presence of defects within their structures and the disorder that is inevitably associated with such defects. It is very interesting to study and understand the defects and disorders in MOFs and to tune the physical properties such as catalysis, gas adsorption, photoluminescence and electronic and mechanical properties.
The overall objective of the project mainly focuses on the intentional synthesis and engineering of defects in MOFs and DMCs, investigation of local and long range of structural defects, heterogeneity, disorder, correlated phenomena and its materials characterization, theory and materials simulation with application and technology relevant for catalysis, gas capture, and separation.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The report provides an overall progress of the research work performed by 15 DEFNET ESRs in 4 scientific works packages and summarizes the training activities of ESRs, as well as the dissemination and project management activities (4 works packages).
WP-1: Synthesis and methods of defect engineering in MOFs: Many synthetic concepts and techniques to tailor and modulate defect engineered MOFs were applied in order to achieve control over the MOF defect structures and properties. For example, a) with UiO-66 types of MOFs, defects were intentionally created by the encapsulation of metal nanoparticles (M-NPs) such as Pd/Pt, Ru/Pt inside the MOF pores (Pd1Pt1@UiO-66; Pd1Pt2@UiO-66; Ru1Pt1@UiO-66); and also by changing the modulator concentration such as acetic acid and trifluoroacetic acid. b) Several double metal cyanides (DMCs) were synthesized by different methods: i) Zn-Co DMCs by standard methods; ii) Zn-Co DMCs using organic compounds as complexing and co-complexing agents; c) New MOF-808 materials have been prepared containing a small amount of defect-inducing linkers, which creates additional active sites such as mixed-linker MOF-808, f) Flexible MOFs such MIL-53 (Cr, Br, Al) type of MOFs and MIL-101-Cr was synthesized following an HF-free method, in combination with the acid-modulation approach;
WP-2: Experimental characterization of MOF structures, defects and disorder: In this work package a) defect-MOFs and DMCs syntheisized in WP-1 were characterized in detail by PXRD, TG, SEM, TEM analysis, N2 physisorption ADF-STEM analysis, UHV-FTIR analysis, XPS analysis and catalytic tests (hydrogenation of benzene, CO oxidation). In addition, sorption capabilities test for a broad range of probing molecular agents (CO2, CH4, …) were also performed. b) Influence of defects on the structural flexibility MOFs in MIL-53(Cr)-Br was studied by PXRD, Differential Scanning Calorimetry (DSC), N2 adsorption studies. c) DE-HKUST-1(Cu) and Ru-containing DE-HKUST-1 (Ru) were characterized by ultrahigh vacuum IR spectroscopy (UHV-FTIRS) apparatus (high-quality IR data with extremely high sensitivity and stability). IR study was complemented by high-resolution XPS (HR-XPS) measurements. The combined UHV-FTIRS and HR-XPS data obtained for DE-HKUST-1(Cu) and Ru-containing DE-HKUST-1 samples demonstrated consistently the presence of two types of defects formed via controlled doping with various defect linkers.
WP-3: Theoretical modelling and materials simulations: a) A reactive force field model for UiO66(Zr)was developed and has implemented ACKS2 (from UGent) into ReaxFF (part of SCM’s materials modelling suite). Progress has also been made to facilitate the derivation of ReaxFF parameters for any other type of material. b) Fischer esterification of Free Fatty Acids (FFA) on UiO-66, a reaction involved in the production of biodiesel (Experimental input: CSIC) was studied with different state of the art modelling techniques, (cluster and periodic ab initio calculations). The reaction has been modelled on pristine and amino functionalized UiO-66, with a focus on the reaction mechanism and the role of active sites and defective coordinating species. A simulation protocol for studying reactions on MOFs has been validated and resulted in computational data that are in full agreement with the experimental observations. c) Force field validation for flexible defective frameworks. Modified/missing building blocks (BBs) are “scrambled” on the topological level. The MOF is synthesyzed in silico, “weaving” its BBs according to the defective augmented topology. Full MM calculations of the defective framework are performed with MOF FF and benchmarked against embedded QM/MM to reproduce the defect region with increased resolution.
WP-4: Application and Benchmarking of Materials: a) Selective aerobic oxidation of cumene to cumylhydroperoxide over bimetallic MOFs; b) Defect-engineered wide pore MOF-808 materials for catalytic applications; c) S

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

MOFs are designed and commonly viewed to be structurally “perfect” like discrete molecules, which however does not give the full structural information. Not much is known about intrinsic structural defects on the molecular scale and the possibilities of intentional generation and tailoring (reactive) “defect” sites in the volume of MOFs. Many catalytic processes, however, are known to happen on recative defect sites on heterogeneous catalyst surfaces. The characterization and the engineering of such sites at the internal surface of MOFs (similar to the internal surface of zeolites) will be of crucial importance for a better understanding of MOFs in general. In particular, the tuning of the chemical and physical nature of such (intentional) defect containing MOFs will open up new combinatorial perspectives for applications in catalysis and gas storage/separation and chemical sensing.
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