Microenvironment Regulation of {Co4IIO4} Cubane for Syngas Photosynthesis.

It is a great challenging task for selectivity control of both CO2 photoreduction and water splitting to produce syngas via precise microenvironment regulation. Herein, a series of UiO-type Eu-MOFs (Eu-bpdc, Eu-bpydc, Rux-Eu-bpdc, and Rux-Eu-bpydc) with different surrounding confined spaces were designed and synthesized. These photosensitizing Rux-Eu-MOFs were used as the molecular platform to encapsulate the [CoII4(dpy{OH}O)4(OAc)2(H2O)2]2+ (Co4) cubane cluster for constructing Co4@Rux-Eu-MOF (x = 0.1, 0.2, and 0.4) heterogeneous photocatalysts for efficient CO2 photoreduction and water splitting. The H2 and CO yields can reach 446.6 and 459.8 µmol·g-1, respectively, in 10 h with Co4@Ru0.1-Eu-bpdc as the catalyst, and their total yield can be dramatically improved to 2500 µmol·g-1 with the ratio of CO/H2 ranging from 1:1 to 1:2 via changing the photosensitizer content in the confined space. By increasing the N content around the cubane, the photocatalytic performance drops sharply in Co4@Ru0.1-Eu-bpydc, but with an enhanced proportion of CO in the final products. In the homogeneous system, the Co4 cubane was surrounding with Ru photosensitizers via week interactions, which can drive water splitting into H2 with >99% selectivity. Comprehensive structure-function analysis highlights the important role of microenvironment regulation in the selectivity control via constructing homogeneous and heterogeneous photocatalytic systems. This work provides a new insight for engineering a catalytic microenvironment of the cubane cluster for selectivity control of CO2 photoreduction and water splitting.