Biaxially extended side-chain conjugation of benzodithiophene-based polymer dots for superior photocatalytic stability under visible-light irradiation

Conjugated polymer dots (Pdots) based on a series of BDT-based polymers with varied biaxially extended side-chain conjugations were prepared and employed for photocatalytic hydrogen production under visible light irradiation from aqueous solutions. The BDT-based polymers consisted of a dithiophedifluorobenzo[c][1,2,5]thiadiazole (DFBT) moiety as the acceptor unit and a BDT unit with different biaxially extended side-chains, including a alkyl-monothienyl group (T), a linear alkyl-dithiophene (2T) group, a branched alkyl-terthiophene (3T) group, and a fused alkyl-benzotrithiophene (B3T) group. The as-prepared Pdots based on these four polymers (PBDT-T, PBDT-2T, PBDT-3T, and PBDT-B3T) showed varied photophysical and electrochemical properties along with distinctive photocatalytic activity and long-term stability. Among them, the PBDT-B3T Pdots were showed to deliver a high photocatalytic efficiency of 14.1 mmol g⁻¹ h⁻¹ and a superior photocatalytic stability over 375 h in the presence of Pt as cocatalyst and ascorbic acid as sacrificial electron donors. Our results revealed that varying the structures of the biaxially extended side-chains endows a great flexibility in the photocatalytic activity of the polymers and the biaxially-extended conjugated side-chains can be a promising design strategy for the conjugated polymer to enhance the photocatalytic activity and stability.