Owing to their highly conjugated structure and central metal ion, which can readily interconvert between different oxidation states to accomplish oxidation and reduction reactions, metalloporphyrins have been selected by Nature to fulfil the two main catalytic phenomena allowing life, i.e. photosynthesis by chlorophylls and respiration by cytochromes. For efficiency and sustainability considerations, it is highly desirable to employ metalloporphyrins in conductive assemblies for heterogeneous catalysis. Nevertheless, due to the lack of synthetic approach, the design and application of conjugated metalloporphyrin assemblies is a largely unexplored topic in view of the plethora of available metalloporphyrin patterns.

Oxidative chemical vapor deposition (oCVD) was recently demonstrated as a convenient method for the simultaneous synthesis and deposition of metalloporphyrin conjugated polymers [1]. In oCVD, the monomer and a suitable oxidant are both supplied from the vapor phase to a surface on which oxidative polymerisation and doping occur in a single step [2]. Metalloporphyrins possessing free meso-positions [1,3,4] and porphyrins bearing thienyl substituents have both been successfully polymerised using oCVD to yield the formation of formation fused metalloporphyrin tapes and thienyl-bridged metalloporphyrins covalent organic frameworks (COFs), respectively. Importantly in the perspective of practical application, including heterogeneous electrocatalysis, the metalloporphyrin conjugated polymers are readily deposited on virtualy any substrate in the form of smooth and thickness-controlled thin films. In addition, metalloporphyrin conjugated polymers are formed almost independently from their substituents [3,4] and central metal cations [3,4] enabling the engineering of their electrocatalytic properties.

Up-to-date, porphyrin conjugated polymer thin films prepared by oCVD have been successfully investigated for the electrochemical hydrogen evolution reaction (HER) [3], nitrate reduction reaction (NRR), oxygen reduction reaction (ORR), oxygen evolution reactions (OER) [4]. Experimental and theoretical data demonstrate the impact of both the central metal cations [3,4] and substituents [3,4] on the catalytic activities [3,4] and stability [5] of the metalloporphyrin conjugated polymer thin films. The approach reported in this work, also suitable for the preparation of heterometallic porphyrin conjugated polymer thin films [6], circumvents many limitations of solution-based approaches and pave the way to the facile engineering and integration of efficient electrocatalysts from metalloporphyrins.