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Porous C

Polymeric carbon nitride (C3N4) is currently the most potential nonmetallic photocatalyst, but it suffers from low catalytic activity due to rapid electron–hole recombination behavior and low specific surface area. The morphology control of C3N4 is one of the effective methods used to achieve higher photocatalytic performance. Here, bulk, lamellar and coralloid C3N4 were synthesized using different chemical methods. The as-prepared coralloid C3N4 has a higher specific surface area (123.7 m2 · g−1) than bulk (5.4 m2 · g−1) and lamellar C3N4 (2.8 m2 · g−1), thus exhibiting a 3.15- and 2.59-fold higher photocatalytic efficiency for the selective oxidation of benzyl alcohol than bulk and lamellar C3N4, respectively. Optical characterizations of the photocatalysts suggest that coralloid C3N4 can effectively capture electrons and accelerate carrier separation, which is caused by the presence of more nitrogen vacancies. Furthermore, it is demonstrated that superoxide radicals (·O2 −) and holes (h+) play major roles in the photocatalytic selective oxidation of benzyl alcohol using C3N4 as a photocatalyst.

Porous C3N4 (PCN) is favored by researchers because it has more surface active sites, higher specific surface area and stronger light absorption ability than traditional g–C3N4. In this study, cerium dioxide nanoparticles (CeO2–NPs) with mixed valence state of Ce3+ and Ce4+ were doped into the PCN framework by a two-step method. The results indicate that CeO2–NPs are highly dispersed in the PCN framework, which leads to a narrower band gap, a wider range of the light response and an improved the separation efficiency of photogenerated charge in PCN. Moreover, the specific surface area (145.69 m2 g−1) of CeO2–NPs doped PCN is a 25.5% enhancement than that of PCN (116.13 m2 g−1). In the experiment of photocatalytic selective oxidation of benzyl alcohol, CeO2–NPs doped porous C3N4 exhibits excellent photocatalytic activity, especially Ce–PCN–30. The conversion rate of benzyl alcohol reaches 74.9% using Ce–PCN−30 as photocatalyst by 8 h of illumination, which is 25.7% higher than that of pure porous C3N4. Additionally, CeO2–NPs doped porous C3N4 also exhibits better photocatalytic efficiency for other aromatic alcohols.