Incorporating a binuclear cobalt polymer into mesoporous TiO2 to construct a new Z-scheme heterojunction for boosting artificial photosynthesis

The construction of photocatalysts with Z-scheme heterojunction structures has been regarded as an effective strategy to enhance catalytic efficiency in artificial photosynthesis. However, the reported Z-scheme heterojunctions usually show small interfacial contact area, which are unbeneficial for highly efficient charge separation. Herein, a host-guest strategy was developed to precisely construct Z-scheme heterojunctions, with which a polymer (Co-2-P) containing binuclear cobalt catalytic centers was incorporated into the pores of mesoporous TiO2, affording a new Z-scheme heterojunction of Co-2-P@TiO2 with surrounding contact interfacial between Co2P and TiO2. As a result, the resulting Co-2-P@TiO2 heterojunction possesses large interfacial contact areas, and thereby exhibits an outstanding photocatalytic activity for the reduction of CO2 to CO with H2O as the electron donor. The CO production rate reaches as high as 139.2 mu mol g(-1) h(-1), which is 4.0, 4.2 and 3.1 times higher than the pristine TiO2, Co-2-P, and a Z-scheme heterojunction of Co-2-P/TiO2 conventionally prepared, respectively. Systematic studies demonstrate that the encapsulation of Co-2-P into the pores of mesoporous TiO2 greatly accelerates charge separation and electron transfer, thus accounting for its enhanced photocatalytic activity. This study paves a new way to design efficient catalysts for artificial photosynthesis.