A true oxygen-linked heptazine based polymer for efficient hydrogen evolution.

Graphical abstract Highlights • An oxygen linked Heptazine polymer (OLHP) was developed for the first time. • Cyameluric acid was explored as polymer precursor for the first time. • Improved charge separation compared g-CN was observed. • 41 times higher hydrogen evolution rate was observed compared to g-CN. Abstract O-doped/functional g-CN polymers are promising materials which have been reported to modify inherent electronic structure and light harvest ability of the g-C 3 N 4 based photocatalysts. However, the doping position and concentration of hetero atom remains ill-defined although enhanced photocatalytic activity of modified g-CN photocatalysts has been reported. Herein, a facile two step procedure to synthesize heptazine polymer with defined O-atom position in polymer structure is presented. Cyameluric acid, a member of cyamelurine family upon polycondensation under inert atmosphere ensures the insertion of O-atom at bridge position between heptazine units in growing polymer. The developed polymer OLHP (oxygen linked heptazine polymer) attains high hydrogen production efficiency likely due to high O-content and efficient charge separation evident from PL spectra compared to g-CN. This heptazine based precursor design also eliminates the possibility of presence of triazine based moiety defects in g-C 3 N 4 polymers. [ABSTRACT FROM AUTHOR]