β-ketoenamine-modified covalent triazine frameworks with extended visible-light absorption for efficient photocatalytic water splitting

Covalent triazine frameworks (CTFs) are promising photocatalysts for water splitting, but weak visible-light absorption and inefficient charge separation caused by intrinsic structural constraints limit their activity. Herein, a β-ketoenamine-based molecule, TpABN, is incorporated into the CTF-1 backbone via low-temperature ionothermal synthesis employing a ZnCl 2 –NaCl–KCl ternary eutectic salt-catalyzed method. This strategy repairs surface defects, suppresses carbonization, and extends the optical absorption edge to ∼700 nm. The resulting keto–triazine donor–acceptor architecture promotes intramolecular charge transfer and prolongs the excited-state carrier lifetime. Consequently, CTF-TpABN achieves a 4-fold higher photocatalytic H 2 evolution rate(3485 ± 64 μmol/g/h) than CTF-MS (without β-ketoenamine modification) and a 27-fold higher rate than CTF-TfOH (synthesized via TfOH catalysis) under visible light (λ > 400 nm, 3 wt% Pt cocatalyst, 10 vol% TEOA). It also shows improved visible-light O 2 evolution (λ > 400 nm, 2 wt% RuO x cocatalyst, 0.05 M AgNO 3 ). These findings highlight CTF-TpABN as a promising visible-light-driven water-splitting photocatalyst and guide CTF-based photocatalyst design.