Tuning the adsorptive and photocatalytic properties of donor-acceptor covalent organic polymers with varying hydroxyl ratios

Covalent organic polymers and frameworks have excellent potential to degrade and eliminate organic pollutants in industrial wastewater. Herein, a family of donor-acceptor covalent organic polymers (D-A COPs) that contain thiazole units and varying amounts of hydroxyl groups from 0 to 100 %, have been designed and synthesized for improved adsorption and photocatalytic performance. Compared with COPs containing hydroxyl groups, NXCOP-3000 without a hydroxyl group is more effective in the adsorption of organic dye pollutants, and the maximum adsorption capacity was 122.5 mg g-1, which is also supported by the theoretical simulation. The more the hydroxyl group content is, the narrower the band gap is in this case. Interestingly, NXCOP-3075 with a 75 % hydroxyl group has demonstrated superior photocatalytic activity, where the dye removal efficiency reaches 98.87 %, which suggests that these COPs create efficient carrier pathways to separate photogenerated holes and electrons efficiently. Therefore, introducing hydroxyl groups into COP can be used as a strategy to enhance photocatalytic activity.