One pot synthesis of hybrid silica aerogels with improved mechanical properties and heavy metal adsorption: Synergistic effect of in situ epoxy-thiol polymerization and sol-gel process

Hybrid material features strongly depend on the synergy between the individual components used during synthesis. To address the current challenges preventing silica aerogels from serving as potential candidates in sustainable chemistry and engineering, we used a novel in situ sulfur-doping synthesis method for silica aerogels to improve the mechanical strength and heavy metal ion adsorption. In this study, three-dimensional monolithic silica aerogels were synthesized using an adaptable one-pot epoxy–thiol reaction to polymerize (3-glycidyloxypropyl)trimethoxysilane and (3-mercaptopropyl)trimethoxysilane, followed by the sol–gel process and supercritical drying. The synergy between the epoxy and thiol groups in the silane precursors with an optimized precursor-to-solvent ratio is crucial for enhancing compressive strength. The cross-linked aerogels had a strong silica hybrid network with high porosity (∼85%–91%), comparable bulk density, and high compressive modulus (∼6.3–20.81 MPa, which is over three orders of magnitude higher than that of traditional tetraethoxysilane-based silica aerogels). The prepared aerogels were then used to remove heavy metals, with Pd²⁺ being adsorbed approximately 100% of the time. The maximum adsorption capacity fitted using the Langmuir adsorption model was 689.65 mg/g. The proposed method offers a new strategy for synthesizing in situ sulfur-doped silica aerogels with enhanced mechanical properties for heavy metal removal.