Polarizing nanostructured objects and high-field DNP enhanced NMR spectroscopy for structural and functional understanding of catalysts – PasseMuraille

Beside technological progresses in materials engineering, widely applicable atomic-scale characterization techniques are needed for the rational design of tomorrow’s materials. Among the variety of analytical tools, Nuclear Magnetic Resonance (NMR) occupies a place of choice as this versatile spectroscopy relies on observables that are by nature local and do not rely on long range order. However, NMR suffers from inherently low sensitivity. Recently, Dynamic Nuclear Polarization (DNP) has propelled itself as a unique game changer to increase the sensitivity of MAS solid-state NMR. Previously precluded NMR experiments are now routinely performed using DNP with signal enhancement of ca. 100, which translates in gain in time by a factor 10’000 (an 1 hour DNP ssNMR experiment is equivalent to one year on a comparable instrument without DNP). Despite successful developments, the application of DNP NMR remains extremely challenging, if not impossible, for the characterization of reactive surfaces. Also, a severe drop of performance is observed around and above the glass transition temperatures (ca 140 K) of conventional solvent matrices. The project’s aim is to design and prepare advanced nanostructured polarizing materials containing tailored biradicals for efficient DNP at high magnetic fields, as to knock down some key limitations to a wider application of DNP MAS ssNMR. The first objective will be to develop nanostructured porous silica and core-shell nanoparticles containing biradicals as efficient polarizing sources. The development of new strategies for DNP MAS NMR at temperatures close to ambient will be the second objective of the project. The structural characterization of highly reactive surfaces such as heterogeneous catalysts containing reactive metallo-alkyls and/or metallo-hydrides fragments by DNP MAS NMR is the third objective of the project. The achievement of any of the goals above will be of high importance, with immediate added value.