Precious-Metal-Free CO2 Photoreduction Boosted by Dynamic Coordinative Interaction between Pyridine-Tethered Cu(I) Sensitizers and a Co(II) Catalyst

Improving the photocatalytic efficiency of a fully noble-metal-freesystem for CO2 reduction remains a fundamental challenge,which can be accomplished by facilitating electron delivery as a consequenceof exploiting intermolecular interactions. Herein, we have designedtwo Cu(I) photosensitizers with different pyridyl pendants at thephenanthroline moiety to enable dynamic coordinative interactionsbetween the sensitizers and a cobalt macrocyclic catalyst. Comparedto the parent Cu(I) photosensitizer, one of the pyridine-tetheredderivatives boosts the apparent quantum yield up to 76 & PLUSMN; 6% at425 nm for selective (near 99%) CO2-to-CO conversion. Thisvalue is nearly twice that of the parent system with no pyridyl pendants(40 & PLUSMN; 5%) and substantially surpasses the record (57%) of thenoble-metal-free systems reported so far. This system also realizesa maximum turnover number of 11 800 & PLUSMN; 1400. In contrast,another Cu(I) photosensitizer, in which the pyridine substituentsare directly linked to the phenanthroline moiety, is inactive. Theabove behavior and photocatalytic mechanism are systematically elucidatedby transient fluorescence, transient absorption, transient X-ray absorptionspectroscopies, and quantum chemical calculations. This work highlightsthe advantage of constructing coordinative interactions to fine-tunethe electron transfer processes within noble-metal-free systems forCO(2) photoreduction.

Automated summary

By exploiting intermolecular interactions to facilitate electron delivery, two Cu(I) photosensitizers with different pyridyl pendants were designed to interact with cobalt macrocyclic catalyst, significantly enhancing the photocatalytic efficiency of a fully noble-metal-free system for CO2 reduction.