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Synthesis of hYbride fuNctionalized and catalyzEd MOFs foR the storaGe of hYdrogen – SYNYERGY

Synthesis of hYbride fuNctionalized and catalyzEd MOFs foR the storaGe of hYdrogen

The main challenge of the SYNERGY project is to highlight the possibility of modifying locally and at the molecular scale the nature and organization of metallo-organic networks by plasma treatments, dry physico-chemical processes renowned for their reliability and their small environmental footprints. The application objective is oriented to H2 storage.

Modification of commercial MOFs by cold plasma for H2 storage.

The functionalization of porous organometallic networks has been a priority research topic in materials chemistry, particularly in France for the past fifteen years. This is due to the strong potential of such materials for improving interface reactions in cracking processes, electrocatalytic reactions, injection control of chemical substitutes, but also and above all in the storage of gases, such as hydrogen. Indeed, to allow these chemical processes to be viable, fast and inexpensive, obtaining large active surfaces is necessary. Solution impregnation, chemical vapor deposition or encapsulation have already been tested for the functionalization of MOF type networks or carbon microstructures.<br />Nevertheless, the main problem of these functionalization methods lies in their margins of use (reduction temperature of the solutions, limited choice of metals, predominant redox potentials) but also in their implementations that are often costly and not very ecological. Thus, new approaches can be considered to overcome these boundaries. Thus the use of controlled plasma processes (density and energy of the reactive species) in the very near future could probably make it possible to remove the technological obstacles to the storage of hydrogen in MOFs. The SYNERGY project offers a highly controlled and less destructive approach to synthesis by modification than those that have been tested before, while promoting the possibility of developing and characterizing completely new materials for hydrogen storage.<br />The research proposed within the SYNERGY project is a world first which aims to revolutionize the storage of hydrogen-energy vector.

It is proposed to carry out within SYNERGY the first elaborations from commercial MOFs, already identified in the literature as being serious candidates for the storage of hydrogen (MOF-5, MIL-53, HKUST-1, ZIF- 8 and 67, basolite F300 and C 300, etc). The consortium has MOF-5, MIL-53, HKUST-1 and ZIF-8 as is. This will make it possible to work with MOFs whose porosity and specific surface vary while taking into account, if they exist, the limits of functionalization and hybridization by impregnation of such networks with the plasma processes used. For example, the non-destructive functionalization of organic ligands, based on terephthalic acid, will allow both the formation of active amine groups (allowing the catalysis of hydrogen evolution reactions) but also to possibly change locally surface energy (Fermi level). This will be achieved by nitriding in an N2/H2 plasma mixture at low pressure and low temperature (< 100°C) in ECR plasma or in NH3 gas in an AP-DBD discharge. The impregnation of the networks will be carried out by HiPIMS plasma in order to ultimately synthesize covalent hydrides or mixed hydrides from alkali metals (Li, Na, K), metalloids (B, Si) and/or aluminum as metal post-transition. Single-phase or core-shell type alloys based on sodium, boron and aluminum will be developed and will be the first to be tested. The idea is to work with light elements (< 41 amu) to eventually allow solid and light storage for stationary and mobile applications. Deposits with very low levels of metal catalysts will be carried out by magnetron sputtering or co-sputtering. Catalysts that are also already well identified, such as palladium (or platinum), will be used primarily as references for the catalysis of HER at the level of MOFs. If possible, the program will then move towards the use of promising and inexpensive nickel-based catalysts such as NiO/Ni heterostructures.
The optimization of these hybrid MOFs will therefore be the result of an iterative study centered on the analysis of the modifications of the MOFs on their texture which will be determined by adsorption of Ar and H2 at 87 and 77 K, respectively, and at pressures up to 0.1 MPa.

Firstly, the proof of concept of the functionalization by pulsed DBD plasma of terephthalic acid, constituent organic materials for the synthesis of MOFs, could be confirmed by crossing the results from thermogravimetric analyzes by mass spectrometry (ATG- MS), structural analyzes by X-ray diffraction (XRD) and chemical analyzes by XPS. These initial results thus lay a solid foundation for the continuation of the SYNERGY project. Secondly, the transferability of the treatment process on MOFs could also be confirmed. Thus, commercial MOFs based on terephthalic acid, such as MOF-5 and MIL53-Al, have undergone a plasma treatment similar to that undergone by terephthalic acid under an NH3 atmosphere. Furthermore, the textural characterization reveals the microporosity of the materials, with a reduction in the specific surface caused by the exposure to ammonia and by the grafting of nitrogen on the material treated by I-DBD, as well as a shrinkage of pore size caused by the breathing effect. This effect therefore has a positive impact on the adsorption at 77 K where we see an improvement in adsorption linked to the pore volume which is greater in the case of the material exposed to NH3 and that treated by plasma than the reference material (figure 3). These results are promising for an optimization of MIL53-Al in use under environmental conditions of pressure and temperature (pressure close to atmospheric pressure, and temperature close to ambient temperature), as well as for developing materials that also make it possible to have a higher adsorption capacity under these conditions.
The SYNERGY project will gradually focus on the second part concerning the HiPIMS plasma impregnation of metals within MOFs for the formation of metal hydrides.

The perspectives of the SYNERGY projects will be revealed once the various research components have been completed.

First article of the SYNERGY project on the results obtained on the functionalization of organic materials used as organic ligands within certain MOFs.

A. Najah, D. Boivin , C. Nöel, L. De Poucques, G. Henrion, S. Cuynet,
Amino-grafting pre-functionalization of terephthalic acid by impulse dielectric-barrier discharge (DBD) plasma for amino-based Metal-Organic Frameworks (MOFs),
Materials Chemistry and Physics, 2022,

The project SYNERGY addresses to the hydrogen storage challenge. It promotes the use generalization of dry plasma processes to achieve in-situ both the functionalization and the hybridization by metal hydrides of the catalyzed MOFs. In these circumstances, the objective is to study conditions of development by cold plasmas of these porous structures in order to get a wide range of functionalized MOFs, at lower cost and ecological. The selected materials will be crucial since they will have to allow the formation of innovative, flexible, safe hybrid materials by integrating ultimately both chimisorption and physisorption properties. The synthesis of these hybrid MOFs will be the result of a detailed parametric study focused on the capabilities to improve the hydrogen evolution reaction.

Project coordinator

Monsieur Stéphane Cuynet (Institut Jean Lamour (Matériaux - Métallurgie - Nanosciences - Plasmas - Surfaces))

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

IJL Institut Jean Lamour (Matériaux - Métallurgie - Nanosciences - Plasmas - Surfaces)

Help of the ANR 269,600 euros
Beginning and duration of the scientific project: February 2021 - 42 Months

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