Epoxy-thiol crosslinking for enhanced mechanical strength in silica aerogels and highly efficient dye adsorption

Abstract

Epoxy-thiol crosslinked silica aerogels were synthesized with (3-glycidyloxypropyl)trimethoxysilane and (3-mercaptopropyl)trimethoxysilane as co-precursors in acid and base catalyzed reactions via in situ epoxy-thiol click polymerization followed by hydrolysis and condensation using tetraethylorthosilicate (TEOS) as a primary precursor. The acid and base-catalyzed aerogels were prepared by varying the TEOS and tetramethylammonium hydroxide mole ratios, while maintaining all other formulations with a constant molar ratio. The acid-catalyzed silica aerogel (TGM) had a notable specific surface area (297 m2/g) and compressive modulus ∼8.5 MPa, whereas the hybrid base-catalyzed silica aerogel (BTGM) appeared to have a relatively high specific surface area (519 m2/g) than the TGM aerogel. In particular, the robustness of BTGM aerogels exhibited a significantly enhanced compressive modulus (11 MPa), and the obtained thermal conductivity was 0.047–0.050 W.m−1.K−1, which was comparable to that of TGM-based aerogels, owing to methoxy groups being hydrolyzed at different rates. The maximum adsorption capabilities for the removal of methylene blue dye, as measured using the Langmuir adsorption model, were 1694.9 mg/g. The isotherm and adsorption kinetics both adhered to Langmuir and pseudo-second order models, respectively. The proposed approach serves as a new strategy for in situ epoxy-thiol click polymerization-based silica aerogels with improved mechanical resilience for pollutant adsorption.