COF/In 2 S 3 S-Scheme Photocatalyst with Enhanced Light Absorption and H 2 O 2 -Production Activity and fs-TA Investigation.

Photocatalytic hydrogen peroxide (H 2 O 2 ) synthesis from water and O 2 is an economical, eco-friendly, and sustainable route for H 2 O 2 production. However, single-component photocatalysts are subjected to limited light-harvesting range, fast carrier recombination, and weak redox power. To promote photogenerated carrier separation and enhance redox abilities, an organic/inorganic S-scheme photocatalyst is fabricated by in situ growing In 2 S 3 nanosheets on a covalent organic framwork (COF) substrate for efficient H 2 O 2 production in pure water. Interestingly, compared to unitary COF and In 2 S 3 , the COF/In 2 S 3 S-scheme photocatalysts exhibit significantly larger light-harvesting range and stronger visible-light absorption. Partial density of state calculation, X-ray photoelectron spectroscopy, and femtosecond transient absorption spectroscopy reveal that the coordination between In 2 S 3 and COF induces the formation of mid-gap hybrid energy levels, leading to smaller energy gaps and broadened absorption. Combining electron spin resonance spectroscopy, radical-trapping experiments, and isotope labeling experiments, three pathways for H 2 O 2 formation are identified. Benefited from expanded light-absorption range, enhanced carrier separation, strong redox power, and multichannel H 2 O 2 formation, the optimal composite shows an impressive H 2 O 2 -production rate of 5713.2 µmol g -1 h -1 in pure water. This work exemplifies an effective strategy to ameliorate COF-based photocatalysts by building S-scheme heterojunctions and provides molecular-level insights into their impact on energy level modulation.