D₁-D₂-A ternary conjugated microporous polymers synthesized via direct CH arylation for enhancing photocatalytic...

Conjugated microporous polymers (CMPs), featured by broad tunability in molecule design, structure and properties, have been widely used as photocatalysts for water splitting to produce hydrogen. However, the conventional donor-acceptor (D-A) binary CMPs have not achieved satisfactory performance so far. In this contribution, a series of D₁-D₂-A ternary CMPs are synthesized by the atom-economical direct CH arylation polymerization (DArP), wherein the dibenzo[b,d]thiophene-S,S-dioxide (BTDO), tetraphenylethylene (TPE) and 3,4-ethylenedioxythiophene (EDOT) units serve as the acceptor (A), donor D₁ and donor D₂, respectively. The structure-property correlations of the CMPs are systematically investigated by optical, electrochemical, water contact angle, and hydrogen production performance tests, revealing that the ternary D₁-D₂-A CMPs can maximize hydrophilicity and charge separation through the synergistic effect of BTDO, EDOT, and TPE building blocks. As a result, the ternary CMP-3 with an optimal D/A ratio achieves the highest photocatalytic hydrogen evolution rate up to 81.4 mmol g^-1 h^-1 without the aid of Pt co-catalyst, which has a 26-fold and 101-fold improvement compared to the pristine D₁-A and D₁-D₂ binary CMPs, respectively. Meanwhile, a high apparent quantum yield of 11.1 % at 500 nm is successfully achieved. Density functional theory calculation discloses that D₁-D₂-A ternary CMPs possess the desirable molecular geometry and superior charge separation. This work provides a new design and synthetic strategy for the high-performance CMP-based photocatalysts.