Accessing Poly(DA-ran-Dπ) Ternary Copolymers via Direct C–H Arylation for Ultrahigh Photocatalytic Hydrogen Production

π-Conjugated polymers (CPs) bearing alternating electron donor–acceptor (D–A) blocks have been widely exploited as promising photocatalysts for hydrogen production. However, little attention has been paid to the D–A ternary polymer photocatalysts, and the current investigations on such a system are mainly focused on the D−π–A type by inserting a π-bridge between the D and A units. Herein, a new type of ternary polymeric photocatalysts, namely poly(DA-ran-Dπ), were designed and facilely constructed via atom-economical direct C–H arylation polymerization (DArP), in which benzothiophene-5,5-dioxide (DBTSO2), 3,4-ethylenedioxythiophene (EDOT), and phenyl serve as acceptor, donor, and π-spacer, respectively. Our findings reveal that the DBTSO2, EDOT, and phenyl building blocks can exert synergic effects on promoting the hydrophilicity, D–A interactions, and charge separation of the resulting ternary CPs. Compared to the binary polymer EDBz-0, the ternary EDBz-25 exhibits a much superior photocatalytic performance, yielding a hydrogen evolution rate up to 241.5 mmol g–1 h–1 with an unprecedented apparent quantum yield of 28.62% at a 500 nm wavelength without the aid of a Pt cocatalyst. The water-displacing setup reveals that 91 mL of H2 gas can be quickly produced within 2 h by using only 3 mg of EDBz-25 as the photocatalyst. The construction of ternary CPs via DArP, developed in the current work, offers a new opportunity for the design and green synthesis of polymeric semiconductors for renewable energy applications.