Decomposition of Organochlorinated Silica Xerogels at High Temperature: A Kinetic Study

Hybrid silica xerogels functionalised with chlorinated organosilanes combine tunable porosity and surface chemistry, making them attractive for applications in sensing, membrane technology, and photonics. The main objective of this work is to investigate the thermal decomposition kinetics of organochlorinated xerogels and to establish a correlation with the released volatile compounds identified in a prior TGA/FTIR/GC–MS study. The materials were synthesised via the sol-gel process using organochlorin-ated alkoxysilane precursors and yielding highly condensed nanostructures in which the precursor nature strongly influences the morphology and textural properties. The N2 adsorption analyses reveal that increasing the precursor content decreases the spe-cific surface area and pore volume while promoting the formation of periodic domains, which are observed even at low organosilane molar percentages. The incorporation of such organic moieties imparts chemical reactivity and flexibility to the silica matrix, although it may also affect thermal stability, which is critical considering that decom-position can release hazardous volatiles such as benzene. A comprehensive thermal characterisation of a series of xerogels containing chloroalkyl and -aryl groups was conducted using TGA coupled to FT–IR and GC–MS, identifying two main decomposi-tion stages and the following order of thermal stability according to the organosilane moiety: 4-chlorophenyl > chloromethyl > 3-chloropropyl > 2-chloroethyl. Kinetic and mechanistic insights were obtained through the Flynn–Wall–Ozawa isoconversional method and Criado master plots, using TGA/DSC measurements under nitrogen at multiple heating rates (5, 10, 20, 30 and 40 K min⁻¹). These results provide a framework for designing thermally stable hybrid materials for advanced technological applications.