Self‐Induced and Progressive Photo‐Oxidation of Organophosphonic Acid Grafted Titanium Dioxide

• Published in: ChemPlusChem (Weinheim, Germany) Vol. 88; no. 3; pp. e202200441 - n/a
• Main Authors: Gys, Nick, Pawlak, Bram, Marcoen, Kristof, Reekmans, Gunter, Velasco, Leticia F., An, Rui, Wyns, Kenny, Baert, Kitty, Zhang, Kaimin, Lufungula, Léon Luntadila, Piras, Alessandra, Siemons, Laurens, Michielsen, Bart, Van Doorslaer, Sabine, Blockhuys, Frank, Hauffman, Tom, Adriaensens, Peter, Mullens, Steven, Meynen, Vera
• Format: Journal Article
• Language: English
• Published: Germany 01-03-2023
• Subjects: ageing; organophosphonic acids; photo-oxidation; surface chemistry; titanium dioxide; titanium dioxide; ageing; surface chemistry; photo-oxidation; organophosphonic acids
• ISSN: 2192-6506; 2192-6506
• DOI: 10.1002/cplu.202200441

While synthesis‐properties‐performance correlations are being studied for organophosphonic acid grafted TiO2, their stability and the impact of the exposure conditions on possible changes in the interfacial surface chemistry remain unexplored. Here, the impact of different ageing conditions on the evolution of the surface properties of propyl‐ and 3‐aminopropylphosphonic acid grafted mesoporous TiO2 over a period of 2 years is reported, using solid‐state 31P and 13C NMR, ToF‐SIMS and EPR as main techniques. In humid conditions under ambient light exposure, PA grafted TiO2 surfaces initiate and facilitate photo‐induced oxidative reactions, resulting in the formation of phosphate species and degradation of the grafted organic group with a loss of carbon content ranging from 40 to 60 wt %. By revealing its mechanism, solutions were provided to prevent degradation. This work provides valuable insights for the broad community in choosing optimal exposure/storage conditions that extend the lifetime and improve the materials′ performance, positively impacting sustainability.
The progressive degradation of organophosphonic acid grafted TiO2 under ambient light in the presence of moisture is reported in this work. The P−C bonds are cleaved in tandem with phosphate formation and oxidation of the carbon chain, while the Ti−O−P bonds remain unaffected.