Regulating morphological and electronic structures of polymeric carbon nitrides by successive copolymerization and stream reforming for photocatalytic CO2 reduction

Abstract

Polymeric carbon nitrides (PCNs) are attractive candidates for diverse photoredox catalysis, but the CO₂ reduction activity of pristine PCNs is unsatisfactory, mainly due to the bulky structure and insufficient optical harvesting. In this work, a facile and efficient strategy coupling copolymerization and stream reforming is developed to exfoliate the bulky PCNs into PCN nanosheets (named PCN-T-NSs). The ameliorated morphological and electronic structures of PCN-T-NSs enable the exposure of abundant catalytically-active sites, accelerated separation of photogenerated charge carriers, and strengthened photoabsorption in the visible region. Consequently, the optimized PCN-T-NS photocatalyst shows a greatly enhanced CO₂ reduction activity, with a remarkable CO-releasing rate of 43 μmol h⁻¹, which is about 40 times greater than that of pristine PCN. Besides, a high apparent quantum efficiency (AQE) of 4.2% is realized by the PCN-T-NS catalyst under 420 nm photoirradiation with TEOA as a sacrificial reagent and Co(bpy)₃²⁺ as a cocatalyst. Moreover, the integrated copolymerization and stream reforming strategy is extendable to the assembly of several other carbon nitride nanosheets with enhanced performance for CO₂ photoreduction by employing the typical comonomers. This work may bring some fresh vitality for constructing well-tailored carbon nitride polymers with functions for sustainable solar-to-chemical energy conversion.