The goal of this project is to achieve a deep understanding of the properties of functional heterostructures formed by deposition of Cobalamin (Vitamin B-12) on graphene or Au(111) surfaces. This is a prototypical "biomimetic" material, that is: a synthetic model of an active biological site, imitating its functionalities. These systems may have very important applications in energy harvesting, conversion and storage. Unlike the flat two-dimensional (2D) metal-organic frameworks grown on graphene or Au(111) and studied in a related project, this material has both a "2D" character (due to the porphyrin group lying over a flat substrate) and a "3D" non-trivial structure, the latter affecting in subtle ways the functionalities of the material. We are interested in particular in the study of the effects of the second coordination sphere of neighbors around the catalytic atom (Co) and how this affects the reactions (notably, O2 and CO2 reduction) that may be catalysed by such system.

This project is conducted in the framework of Italian PRIN-PNRR project “Shedding light where 2D materials go 3D: energy transfer and second coordination sphere at biomimetic model surfaces”, in close collaboration with the experimental UniTs (Trieste University) unit, led by Prof. Erik Vesselli, that provides fabrication and spectroscopic data for these new material. Collaboration is also envisaged with theoreticians in UniTs, led by Prof. Maria Peressi, who have already investigates similar materials.

The specific work consists in the numerical simulations of the mentioned material, using first-principle density functional theory (DFT) techniques. The simulation protocol: choice of the exchange-correlation functional, cell size, computational requirements, etc., will be first established, building upon previous experience in the UniTs group. Hubbard-corrected functionals (DFT+U) are expected to yield an acceptable quality of simulations. The determination of a suitable reduced model of the 3D structure is a pre-requisite in order to obtain realistic results at a reasonable computational price.

As a further step, and depending upon the results of the experiments, we will study of the interactions of the material with O2 and CO2 molecules, possibly under realistic conditions of temperature and pressure. The results will be analyzed and compared with experiments, discrepancies will be understood and hopefully resolved.

Some experience with DFT calculations on high-performance computers, preferably with the Quantum ESPRESSO suite, is required.

References:

Taking on the turnover challenge, R. J. Hooley, J. Nat. Chem. 2016, 8, 202.

Second-Sphere Biomimetic Multipoint Hydrogen-Bonding Patterns to Boost CO₂ Reduction of Iron Porphyrins, P. Gotico et al., Angew. Chemie Int. Ed. 2019, 58, 4504.

Single Metal Atom Catalysts and ORR: H‑Bonding, Solvation, and the Elusive Hydroperoxyl Intermediate F. Armillotta et al., ACS Catal. 2022, 12, 7950−7959

Spectroscopic fingerprints of iron-coordinated cobalt and iron porphyrin layers on graphene F. Armillotta et al., Cell Reports Physical Science 4, 101378, May 17, 2023