In-situ synthesized porphyrin polymer/TiO composites as high-performance Z-scheme photocatalysts for CO conversion.

The promising photocatalytic conversion of CO into valuable fuel promotes the development of photocatalyst through various methods. In this work, TiO nanoparticle was composited with covalent porphyrin polymers (COP-Ps) to fabricate composite photocatalysts. The resultant COP-Ps/TiO composites by in situ hydrothermal method exhibit much improved photocatalytic activity for the conversion of CO into CO relative to two components, and it is attributable to improved charge transfer between two moieties led by strong interaction. Especially, TiO is composited more evenly with the sulfonated hollow COP-P (sh-COP-P). The resultant composite sh-COP-P/TiO performs best with a CO production rate of 5.70 μmol·g·h, which is approximately 20.4 times as high as that of pure TiO and 2.3 times of sh-COP-P polymer. For comparison, the simple physical mixture of sh-COP-P and TiO (sm-sh-COP-P/TiO) was fabricated, and it performs more badly due to poor mixing uniformity. A Z-scheme photocatalytic mechanism was proposed for sh-COP-P/TiO composite on the basis of energy band analysis and hydroxyl radical test. This study provides a new in situ strategy to fabricate organic polymer/metal oxide composites of high photocatalytic activity for CO reduction.