Visible‐light‐driven CO2 reduction to valuable chemicals without sacrificial agents and cocatalysts remains challenging, especially for metal‐free photocatalytic systems. Herein, a novel donor–acceptor (D–A) covalent organic framework (CT‐COF) was constructed by the Schiff‐base reaction of carbazole‐triazine based D–A monomers and possessed a suitable energy band structure, strong visible‐light‐harvesting, and abundant nitrogen sites. CT‐COF as a metal‐free photocatalyst could reduce CO2 with gaseous H2O to CO as the main carbonaceous product with approximately stoichiometric O2 evolution under visible‐light irradiation and without cocatalyst. The CO evolution rate (102.7 μmol g−1 h−1) was 68.5 times that of g‐C3N4 under the same conditions. In situ Fourier‐transform (FT)IR analysis indicated that CT‐COF could adsorb and activate the CO2 and H2O molecules and that COOH* species may be a key intermediate. DFT calculations suggested that nitrogen atoms in the triazine rings may be photocatalytically active sites.
A simple one‐step pyrolysis process (compared with the routine method of liquid exfoliation and impregnation) was designed to synthesize Fe‐doped graphitic carbon nitride (g‐C3N4) nanosheets with NH4Cl as dynamic gas template and FeCl3 as the Fe source. Results of XPS and DRS indicated that the Fe species might exist at the state of Fe3+ and form Fe−N bonds with N atoms, thereby expanding visible light absorption regions and reducing the band gap of g‐C3N4 nanosheets. Doping certain amounts of Fe could promote the exfoliation and further increase the specific surface area, while excessive Fe might break the sheet structure. The specific surface area of the optimized Fe‐doped g‐C3N4 nanosheets reached 236.52 m2 g−1, which was 2.5 times higher than that of g‐C3N4 nanosheets. Among various photocatalysts prepared, the sample (0.5 wt % FeCl3) exhibited maximum photocatalytic performance in degradation of Methylene Blue and water splitting under visible light irradiation. The degradation rate of MB was about 1.4 and 1.7 times higher than that of pure g‐C3N4 nanosheets and bulk g‐C3N4, respectively. The H2 production rate was 536 μmol h−1 g−1, which was 1.8 and 6 times higher than that of pure g‐C3N4 nanosheets and bulk g‐C3N4, separately.
To tackle severe environmental pollution, a search for materials by economical and eco-friendly preparations is demanding for public health. In this study, a novel in situ method to form silver nanoparticles under mild conditions was developed using biomimetic reducing agents of polydopamine coated on the rodlike mesoporous silica of SBA-15. The synthesized SBA-15/polydopamine (PDA)/Ag nanocomposites were characterized by a combination of physicochemical and electrochemical methods. 4-Nitrophenol (4-NP) and methylene blue (MB) were used as models for the evaluation of the prepared nanocatalysts of SBA-15/PDA/Ag in which the composite exhibited enhanced catalytic performance toward degrading 4-NP in solution and MB on the membrane, respectively. Additionally, compared with that of solid core-shell SiO/PDA/Ag, tubular SBA-15/PDA/Ag showed the prolonged inhibitory effect on microbial growth as typified by Escherichia coli (60 h), Staphylococcus aureus (36 h), and Aspergillus fumigatus (60 h), which demonstrated efficient control of silver nanoparticles release from the mesopores. The constructed dual-functional SBA-15/PDA/Ag as the long-term antimicrobial agent and the catalyst of industrial products provides an integrated nanoplatform to deal with environmental concerns.
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