Avance 3

For carbon source investigation with isotopic labelled ¹³CH₄: 20 mg Cu_0.029-def-WO₃ photocatalyst was dispersed in 3 mL H₂O, then the reactor was vacuumed for 30 min and refilled with 1 bar O₂ and 5 bar ¹³CH₄. The reaction was conducted for 6 h to gain more concentrated products for detection facilitation. As H¹³CHO tended to exist as HO¹³CH₂OH in aqueous solution, the products were identified by ¹³C NMR (AVANCE III, JEOL Ltd).
For oxygen source investigation with isotopically labelled ¹⁸O₂: 20 mg Cu_0.029-def-WO₃ photocatalyst was dispersed in 3 mL H₂O, then the reactor was vacuumed for 30 min and refilled with 1 bar ¹⁸O₂ and 19 bar CH₄. The reaction was conducted for 6 h to gain more concentrated products for detection facilitation. The as-produced HCH¹⁸O was measured with GC-MS (QP2020, Shimadzu Co., Ltd) equipped with the Cap WAX column to identify the existence of H₂¹⁸O.
For oxygen source investigation with isotopic labelled H₂¹⁸O: 20 mg Cu_0.029-def-WO₃ photocatalyst was dispersed in 3 mL H₂O, then the reactor was vacuumed for 30 min and refilled with 1 bar ¹⁸O₂ and 19 bar CH₄. The reaction was conducted for 6 h to gain more concentrated products for detection facilitation. The as-produced HCH¹⁸O was measured with GC-MS (QP2020, Shimadzu Co., Ltd) equipped with the Cap WAX column to identify the existence of H₂¹⁸O.

MS data were measured on the JEOL MS Station JMS-700 spectrometer or JEOL 600 MS Route spectrometer. High-resolution mass spectra were recorded on a Micromass-Q-TOF-Ultima-3-mass spectrometer (Waters) with lockspray interface and a suitable external calibrant. NMR spectra were recorded on a Bruker Avance III (¹H-NMR: 600 MHz and ¹³C-NMR: 151.1 MHz), JEOL spectrometers (¹H-NMR: 500 MHz and ¹³C-NMR 125 MHz), or a Bruker Avance AV-400spectrometer (¹H-NMR: 400 MHz and ¹³C-NMR 100 MHz). The chemical shifts were reported in parts per million (ppm) with TMS as internal standard. Deuterated solvents, methanol (CD₃OD), dimethyl sulfoxide (DMSO-d₆), pyridine (C₅D₅N), and chloroform (CDCl₃) were used as solvents for the NMR experiments. CC was performed with silica gel 60 F254 (70–230 mesh; Merck) and gel permeation with Sephadex LH-20 gel. TLC was carried out with precoated silica gel Kieselgel 60 F254 plates (0.25 mm thick), and spots were detected with UV light (254 and 366 nm) and further sprayed with 20% H₂SO₄ reagent followed by heating at 100°C.