Photocatalytic Abstraction of Hydrogen Atoms from Water Using Hydroxylated Graphitic Carbon Nitride for Hydrogenative Coupling Reactions

Abstract

Employing pure water, the ultimate green source of hydrogen donor to initiate chemical reactions that involve a hydrogen atom transfer (HAT) step is fascinating but challenging due to its large HÀ O bond dissociation energy (BDE H-O = 5.1 eV). Many approaches have been explored to stimulate water for hydrogenative reactions, but the efficiency and productivity still require significant enhancement. Here, we show that the surface hydroxylated graphitic carbon nitride (gCNÀ OH) only requires 2.25 eV to activate HÀ O bonds in water, enabling abstraction of hydrogen atoms via dehydrogenation of pure water into hydrogen peroxide under visible light irradiation. The gCNÀ OH presents a stable catalytic performance for hydrogenative NÀ N coupling, pinacol-type coupling and dehalogenative CÀ C coupling, all with high yield and efficiency, even under solar radiation, featuring extensive impacts in using renewable energy for a cleaner process in dye, electronic, and pharmaceutical industries.

Mesoporous Carbon Nitride with π-Electron-Rich Domains and Polarizable Hydroxyls Fabricated via Solution Thermal Shock for Visible-Light Photocatalysis

“…The vibrational bands at ca. 1160 cm –1 for tsCN- x originate from the presence of C–O bonds . With increasing the amount of glucose, the stretching mode of C–N undergoes an apparent redshift from 1233 to 1250 cm –1 (Figure c).…”

“…The XPS spectra of the C 1s orbital can be divided into three peaks centered at 284.8, 286.5, and 288.4 eV, belonging to C–C, C-NH x /C–O, and NC–N, respectively. , With increasing the content of glucose, the peak area ratios of C–C to NC–N and C-NH x /C–O to NC–N increase gradually (Figure d), suggesting that hydroxyls are formed and nitrogen atoms in NC–N are displaced by carbon atoms. The XPS spectra of the N 1s orbital can be divided into three peaks at 398.6, 399.9, and 401.0 eV, corresponding to the C–NC, N–C 3 , and C-NH, respectively . The peak area ratios of C–NC to N­(C) 3 decrease from 5.0 for CN-bulk to 4.0 for tsCN-50 (Figure e), indicating that the proportion of C–NC bonds decreases.…”

“…1160 cm −1 for tsCN-x originate from the presence of C−O bonds. 32 With increasing the amount of glucose, the stretching mode of C−N 33 undergoes an apparent redshift from 1233 to 1250 cm −1 (Figure 3c). What's more, the intensity of the −NH 2 stretching mode at 3200 cm −1 decreases, while the intensity of the −OH stretching mode at 3300 cm −1 increases.…”

“…The XPS spectra of the N 1s orbital can be divided into three peaks at 398.6, 399.9, and 401.0 eV, corresponding to the C−N�C, N−C 3 , and C-NH, respectively. 32 The peak area ratios of C−N�C to N(C) 3 decrease from 5.0 for CN-bulk to 4.0 for tsCN-50 (Figure 3e), indicating that the proportion of C−N�C bonds decreases. Therefore, the carbon-doping site is the N of C−N�C in heptazine within tsCN-x skeletons, confirming the introduction of π-electron-rich domains into the heptazine-based frameworks.…”

Cyanamide-defect-induced built-in electric field in crystalline carbon nitride for enhanced visible to near-infrared light photocatalytic activity

“…16,17 Due to these attractive properties, especially its easy operability, a great deal of research into CN has been reported for photocatalytic applications, such as water splitting, industrial chemical synthesis, environment protection, etc. 18,19 However, the unmodified CN has low polymerization and low crystallinity, along with sluggish photogenerated electron and hole dynamics. Effective methods to overcome these drawbacks have been realized by regulating the electronic structure of carbon nitride by methods such as copolymerization with small organic molecules and assembly with other semiconductors to construct heterojunction or D-A systems.…”