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Utilizing photocatalytic CO 2 reduction presents a promising avenue for combating climate change and curbing greenhouse gas emissions. However, maximizing its potential hinges on the development of materials that not only enhance efficiency but also ensure process stability. Here, we introduce Hiroshima University Silicate-7 (HUS-7) with immobilized Ti species as a standout contender. Our study demonstrates the remarkable photocatalytic activity of HUS-7 in CO 2 reduction, yielding substantially higher carbonaceous product yields compared to conventional titanium-based catalysts TS-1 and P25. Through thorough characterization, we elucidate that their boosted photocatalytic performance is attributed to the incorporation of isolated Ti species within the silica-based precursor, serving as potent photoinduced active sites. Moreover, our findings underscore the crucial role of the Ligand-to-Metal Charge Transfer (LMCT) process in facilitating the photoactivation of CO 2 molecules, shedding new light on key mechanisms underlying photocatalytic CO 2 reduction., (© 2024 The Authors. ChemSusChem published by Wiley-VCH GmbH.)

Graphitic carbon nitride (C 3 N 4 ) was synthesised from melamine at 550 °C for 4 h in the argon atmosphere and then was reheated for 1-3 h at 500 °C in argon. Two band gaps of 2.04 eV and 2.47 eV were observed in all the synthetized materials. Based on the results of elemental and photoluminescence analyses, the lower band gap was found to be caused by the formation of vacancies. Specific surface areas of the synthetized materials were 15-18 m 2 g -1 indicating that no thermal exfoliation occurred. The photocatalytic activity of these materials was tested for hydrogen generation. The best photocatalyst showed 3 times higher performance (1547 μmol/g) than bulk C 3 N 4 synthetized in the air (547 μmol/g). This higher activity was explained by the presence of carbon (V C ) and nitrogen (V N ) vacancies grouped in their big complexes 2V C  + 2V N (observed by positron annihilation spectroscopy). The effect of an inert gas on the synthesis of C 3 N 4 was demonstrated using Graham´s law of ammonia diffusion. This study showed that the synthesis of C 3 N 4 from nitrogen-rich precursors in the argon atmosphere led to the formation of vacancy complexes beneficial for hydrogen generation, which was not referred so far., (© 2022. The Author(s).)