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Polymeric graphitic carbon nitride (g-CN) has attracted tremendous attention as a promising visible-light-responsive photocatalyst. Although the degree of polymerization (DP) of g-CN is the foundation to determine its physicochemical properties, its effect on the photocatalytic activity still remains elusive. Herein, a well-controlled synthetic route was employed to prepare pristine g-CN with DPs regulated to a certain extent but excludes additional factors like heteroatom doping, surface area, and structural modification. In particular, we updated the X-ray photoelectron spectroscopy analysis based on the recent theoretical/experimental results, providing a reasonable identification of specific chemical bonding states that are in line with the corresponding DP variations. This allows us to correlate the DP evolution of pristine g-CN with its photocatalytic activity, unveiling the trade-off mechanism between visible-light absorption and defective catalytic sites. The average DPs of the synthesized g-CN samples have been roughly estimated based on the molecular formula of (C 6 N 7 ) n (NH 2 ) n +2 (NH) n −1, which is supposed to be adjusted in the range of 4 ≤ n ≤ 10 by changing the condensation time from 1 to 12 h. The sample thermally condensed for 4 h exhibits an optimal visible-light activity for degradation of dyes, with a rather low average DP estimated to be n = 4–5.
Li et al. (Tue,) studied this question.