Photoinduced morphological transformation of a self-assembled iron(ii) coordination polymer: high-performance, non-precious metal, and self-enhancing photocatalytic CO2 reduction

Transition metal coordination polymers are emerging as attractive heterogeneous catalysts for light-driven CO2 reduction. Various coordination polymers have been investigated in photocatalytic CO2 reduction. However, it is challenging to develop robust and non-precious metal-based coordination polymers for CO2 reduction. Moreover, photoinduced morphological transformation of a coordination polymer has yet to be unveiled in optimizing photocatalytic performance. Herein, we report a self-assembled Fe(ii) coordination polymer for high-performance photoreduction of CO2 to CO. This coordination polymer undergoes photoinduced morphological transformation from nanoplate to nanosphere during photocatalysis, resulting in uncommon self-enhancing photocatalysis. After five cycles of reaction, CO is generated with a high yield of 180 mmol g−1 and selectivity of 99.4% in water-containing media. The apparent quantum yield for CO generation is found to be as high as 11.7% at 420 nm. Detailed photoelectrochemical studies demonstrate that nanospheres of the iron(ii) coordination polymer show more exposed active sites and more efficient charge separation and transfer, which is responsible for the self-enhancing photocatalysis. This work presents a robust photocatalytic system for CO2 reduction and also provides unique insight into the morphological transformation of a coordination polymer-based heterogeneous catalyst in photocatalytic CO2 reduction.