D-orbital electronic configuration-dependent photocatalytic CO2 reduction activity of noble metal-free terpyridine-based supramolecular assemblies

Coordination non-noble metal ions in terpyridine-based supramolecular photocatalysts can promote the charge directional transfer towards metals and reduce the enriched CO2. Whether all non-noble metal can play this role and how the electronic structure of metal regulates the activity? Here, a series of photocatalysts were constructed by self-assembly of terpyridine-based molecules and non-noble metals (Zn2+, Co2+, Ni2+ and Cd2+) through coordination interactions and n-n stacking interactions. Study results showed that unpaired d electrons in Co2+ and Ni2+ induce photogenerated electrons deactivation which cannot be used for CO2 reduction through ligand to metal charge transfer (LMCT) process, reflected in low CO evolution rates of 4.07 and 4.30 mu mol g-1 h-1. However, Zn2+ and Cd2+ with filled d10 configurations do not participate in LMCT and activities improve to 46.54 and 38.51 mu mol g-1 h-1. This work offers guidance for designing an efficient photocatalyst by tuning the central metals.