Spectroscopic fingerprints of iron-coordinated cobalt and iron porphyrin layers on graphene

Achieving design capabilities of monolayer 2D functional catalysts represents a challenging perspective. Coordinated single metal atom sites can offer tailored electronic configuration, ligation geometries, chemical activity and selectivity, together with stability. We report spectroscopic evidence of the formation of a 2D metal-organic framework supported by a single graphene sheet in which coordination among Tetra-Pyridyl-Porphyrins (TPyPs) is spontaneously obtained by exploiting single iron atoms. The spectroscopic characterization, together with ab initio methods, reveals that metal inter-molecular coordination occurs via the terminal nitrogen atoms contained in the pyridinic residues of adjacent TPyPs. Interestingly, the peripheral coordination of metal atoms is found to affect the electronic configuration of the porphyrins core. Due to the chemical stability of the supporting graphene layer, its weak interaction with the metal-organic framework, and the known electrochemical activity of the latter, this system represents an optimal candidate for the design and engineering of prototype 2D electrocatalytic materials.