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 π-π 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 μmol 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 μmol g−1 h−1. This work offers guidance for designing an efficient photocatalyst by tuning the central metals.