Unique Z-scheme carbonized polymer dots/Bi4O5Br2 hybrids for efficiently boosting photocatalytic CO2 reduction

• Unique 0D/2D CPDs/Bi 4 O 5 Br 2 direct Z-scheme heterojunction is designed. • The CPDs/Bi 4 O 5 Br 2 can effectively facilitate the migration and separation efficiency of photogenerated carriers. • The 8 wt% CPDs/Bi 4 O 5 Br 2 exhibits the maximal CO production of 132.42 μmol h −1 g −1 under Xe lamp irradiation. • The CPDs can broaden the light utilization range, and promote adsorption of CO 2 and intermediate COOH* as well as desorption of product CO. Constructing heterojunctions with matched band semiconductor is regarded as effective strategy to promote high-efficiency photocatalytic CO 2 reduction. Herein, 0D/2D direct Z-scheme heterojunction involving carbonized polymer dots and Bi 4 O 5 Br 2 nanosheets (CPDs/Bi 4 O 5 Br 2 ) is designed and fabricated, which effectively facilitate migration and separation efficiency of photogenerated carriers and retain more negative electron reduction potential of CPDs and more positive hole oxidation potential of Bi 4 O 5 Br 2 . Moreover, CPDs promote adsorption of CO 2 and intermediate COOH* as well as desorption of product CO. The direct Z-scheme mechanism of CPDs/Bi 4 O 5 Br 2 is collaboratively confirmed by theory calculation, X-ray photoelectron spectroscopy and time-resolved transient absorption spectroscopy. The 8 wt% CPDs/Bi 4 O 5 Br 2 exhibits the maximal CO production of 132.42 μmol h −1 g −1 under Xe lamp irradiation, 5.43 fold higher than that of Bi 4 O 5 Br 2 nanosheets. The CPDs with up-conversion properties can broaden light utilization range, so that composite material also show better CO 2 conversion performance when excitation wavelength is greater than 580 nm.