Diaza-substitution on dibenzothiophene sulfone-based linear conjugated polymers for highly efficient visible-light photo-catalytic hydrogen evolution via substituted-position optimization

Abstract

Two linear conjugated polymers (FSO-TPmT and FSO-TPzT) were synthesized based on dibenzothiophene sulfone and diaza-substituted thiophene-benzene-thiophene with different substituted positions (1,3-diaza-substitution and 1,4-diaza-substitution) for photo-catalytic hydrogen evolution. The 1,2-diaza-substituted polymer (FSO-TPaT) reported from previous work was also used for comparison. The diaza-substitution significantly affected the optical properties, exciton lifetime, charge transport resistance, photo-current response, and thus photo-catalytic performances. Conjugated polymers with 1,3-diaza-substitution exhibited the best photo-catalytic performances with the hydrogen evolution rates (HERs) of 7645 μmol g−1 h−1 and 7280 μmol g−1 h−1 under UV–Vis (>295 nm) and visible light (>420 nm) irradiation, respectively. Moreover, the photo-catalytic performance was further optimized by loading 3 wt% Pt with a HER of 9828 μmol g−1 h−1. The apparent quantum yields were 5.8% and 3.9% at 420 nm and 500 nm, respectively. These results indicated that the conjugated polymer with 1,3-diaza-substitution was mainly active under visible light and should be an excellent visible-light photo-catalyst for hydrogen evolution from water.