Quaternized Side Chain: A Hydrophilic Strategy for\nBoosting the Visible-Light Catalytic Hydrogen Evolution of Linear\nConjugated Polymers

Conjugated\npolymers are emerging as promising organic photocatalysts\nfor visible-light catalytic hydrogen evolution from water. Herein,\na hydrophilic strategy enabled by quaternized side chains is demonstrated\nto boost the photocatalytic hydrogen evolution rate from water. Three\nlinear conjugated polymers with side chains of alkylation, tertiary\namine, and quaternary ammonium were designed and synthesized based\non phthalimide and thiophene–pyridine–thiophene. Compared\nto conjugated polymers with alkylated and tertiary aminated side chains,\nthe quaternized side chain polymer exhibited a significantly smaller\nintact angle, which endowed the photocatalyst with improved hydrophilicity,\nbetter dispersity, and reduced charge transport resistance. Consequently,\nan 8-fold enhancement in the photocatalytic performance was achieved\ncompared to the conjugated polymer with an alkylated side chain. Furthermore,\nthe photocatalytic performances were further optimized, achieving\na hydrogen evolution rate as high as 11608 μmol g<sup>–1</sup> h<sup>–1</sup> when Pt (1 wt %) was used as the cocatalyst.\nThis work indicated that incorporating a quaternized side chain is\nan effective strategy to boost the photocatalytic performances of\norganic photocatalysts.