A Novel 1,1,6,6-Tetracyano hexatriene Linked Conjugated Microporous Polymer for High Photocatalytic Hydrogen Evolution

Abstract

We report the synthesis of a novel 1,1,6,6-tetracyanohexatriene (TCHT) linked conjugated microporous polymer (TCHT-P), through a double [2+2] cycloaddition-retroelectrocyclization (CA-RE) reaction of tetracyanoethylene with tris(4-ethynylphenyl) amine. Strong D-A interactions in TCHT-P lead to broad, near-infrared (NIR) absorption extending the red-edge to ~1230 nm and to radical character. TCHT-P as photocatalysts in a water splitting reaction with Pt co-catalyst, demonstrated an exceptional hydrogen evolution rate of 32,000 µmol g-¹ in 12 hours. The outstanding photocatalytic performance of the polymer originates from strong D-A interactions and nitrile functionalities, which significantly enhance hydrophilicity, charge separation efficiency, and co-catalyst binding. The spatial separation of photogenerated electrons and holes at distinct donor and acceptor sites leads to effective charge accumulation and a dramatic improvement of overall solar-to-hydrogen conversion efficiency. 1,1,4,4-tetracyanobutadiene integrated reference polymer (TCBD-P) showed a red-edge at ~1050 nm, a band gap of 1.60 eV, and photocatalytic hydrogen production of 11,000 µmol g-¹ in 12 hours, highlighting the superiority of TCHT linkages. To our knowledge, these are the first examples of TCBD/TCHT-integrated polymers reported for HER studies.