Turning Imperfections into Assets: Defect‐Engineered Conjugated Polymers for Benchmark Photocatalytic Hydrogen Evolution

ABSTRACT Structural defects in conjugated polymers are traditionally perceived as detrimental charge traps that impair optoelectronic performance. Here, we demonstrate a counterintuitive “defect‐enabled” strategy for benchmark photocatalytic hydrogen evolution. Two donor (D)–acceptor (A) linear conjugated polymers (P‐s and P‐d) are synthesized via Suzuki–Miyaura polycondensation (P‐s) and direct arylation polymerization (P‐d), using dibenzothiophene‐S, S‐dioxide (DBTO) and 10‐methylphenothiazine as A and D units, respectively. A comprehensive solid‐state 13 C NMR, XPS, Raman, and elemental analysis methodology is established to quantify structural defects, specifically A–A homo‑coupling (DBTO–DBTO) junctions that deviate from the ideal alternating D–A structure in these insoluble polymers. Remarkably, P‐d exhibits approximately five‐fold higher defect density (32.4% vs. 6.5%). This defect‐induced DBTO enrichment simultaneously narrows the bandgap (1.81 vs. 2.10 eV), accelerates charge separation (evidenced by TRPL, TAS, and EIS), and provides abundant active sites (DFT‐identified oxygen sites with ΔG H ≈ 1.38 eV). As a result, P‐d achieves an outstanding hydrogen evolution rate of 476.38 mmol h − 1 g − 1 (with 2 wt.% Pt and 0.5% NP‐40), surpassing most reported linear conjugated polymer photocatalysts. This work establishes a clear structure–property correlation for structural defects in polymeric photocatalysts and introduces a rational defect‐engineering strategy for designing high‐performance energy conversion materials.