Conservation of Nickel Ion Single‐Active Site Character in a Bottom‐Up Constructed π‐Conjugated Molecular Network

Abstract

On-surface chemistry holds the potential for ultimate miniaturization of functional devices. Porphyrins are promising building-blocks in exploring advanced nanoarchitecture concepts. More stable molecular materials of practical interest with improved charge transfer properties can be achieved by covalently interconnecting molecular units. On-surface synthesis allows to construct extended covalent nanostructures at interfaces not conventionally available. Here, we address the synthesis and properties of covalent molecular network composed of interconnected constituents derived from halogenated nickel tetraphenylporphyrin on Au(111). We report that the π-extended two-dimensional material exhibits dispersive electronic features. Concomitantly, the functional Ni cores retain the same single-active site character of their single-molecule counterparts. This opens new pathways when exploiting the high robustness of transition metal cores provided by bottom-up constructed covalent nanomeshes.

Surface Electronic Properties-Driven Electrocatalytic Nitrogen Reduction on Metal-Conjugated Porphyrin 2D-MOFs

“…An added advantage is the reducing nature of the porphyrin ligand, which has been highlighted in the study by Hegg et al wherein the porphyrin ligands induce the reduction of N 2 to NH 3 . It is also important to note that the metal center in the metalloporphyrin MOFs also serves as a single-atom catalyst (SAC) as the four nitrogen atoms in the porphyrin network form a highly stable M–N 4 complex, thereby avoiding metal aggregation or migration. , The single-atom nature of the Fe center in metalloporphyrin MOFs has been affirmed from the work by Zhang et al when PCN-222­(Fe) MOF comprised of (iron­(III)­meso-tetra­(4-carboxyphenyl)­porphyrin chloride) and H 2 -TCPP (tetra­(4-carboxyphenyl)­porphyrin) showed an excellent electrocatalytic NRR yield of 1.56 × 10 –11 mol cm –2 s –1 with a Faradaic efficiency (FE) of 4.51% at −0.05 V vs reversible hydrogen electrode (RHE). The nitrogen reduction has been guided by the atomically dispersed Fe site and the porous nature of the MOF, thereby providing accessible active sites .…”