Advancing n-π* electron transition of carbon nitride via distorted structure and nitrogen heterocycle for efficient photodegradation: Performance, mechanism and toxicity insight

To adequately utilize solar energy for water pollution remediation, tailoring graphite carbon nitride (CN) with sufficient active sites exposure, visible-light harvest and eminent charge separation/migration/recombination efficiency, has long been pursuing. Herein, a pyrazine doped distorted architecture CN with advancing n-π* electron transition was tailored via one-pot thermal-melting assemble following thermal-induce copolymerization of pyrazine-2,3-dicarboxylic acid and urea. Various characterizations verify the successful construction of distorted porous thin wall CN. The nitrogen adsorption-desorption, photoelectric and band structure analysis manifest that the optimized 20-PACN sample possesses propelled visible-light capture ability with wavelength above 500 nm, more active sites exposure with high specific surface area and hybrid electron structure with distinctly improved charge separation/migration/recombination efficiency. More importantly, 10 mg of 20-PACN can photodegradation 97 % of tetracycline (91 % of rhodamine B or 91 % of methylene blue) within 100 min, which is 7.1 times of bulk counterparts. ESR and quenching tests confirm that apart from h+, ⋅O2- and 1O2 significantly assist to the photodegradation reaction, which profit from upshifted CB and the appearance of intermediate state. The mass spectrum, toxicity prediction and on-line infrared spectroscopy explicated intermediates, routes and toxicity, as well as real-time monitor the variation of functional groups during photodegradation reaction. At last, combined the above test characterization and density functional theory analysis, a potential propelled mechanism of photodegradation was proposed.