One-pot synthesis of rationally-designed flexible, robust, and hydrophobic ambient-dried molecularly-bridged silica aerogels with efficient and versatile oil/water separation applications

The implementation of silica aerogels (SAs) in numerous applications remains limited due to their costly fabrication process and poor mechanical properties. In order to address these issues, herein, we report the rational design and synthesis of twist-able, stretchable, compressible, and highly hydrophobic bridged SAs (BSAs) through an environmentally friendly one-pot process and cost-effective ambient pressure drying. The green thiol-ene reaction was employed to synthesize bis-silane precursors using different linkers. These molecular spacers influenced the sol-gel process and the resulting BSAs' physico-chemical, morphological, and surface properties, including ultra-low density, high porosity, and large specific surface area. Therefore, comprehensive analyses were conducted to better understand their structure-properties relationship. Owing to the flexible molecular bridges and abundant methyl groups introduced in the silica network, BSAs are mechanically resilient and can withstand 200 cyclic fatigue tests at a compressive strain of 80% without fracture. BSAs also exhibited excellent stretchability, achieving up to 47% elongation at break. Ascribed to the hydrophobic bridges' segments and methyl groups, BSAs are superoleophilic and highly hydrophobic (water contact angle: up to 146.5°). Squeezable and shapable BSAs provided outstanding oil sorption and (continuous) oil/water separation performances, including fast sorption rate, large capacity, ultrahigh flux, and efficient demulsification. BSAs' robustness, evidenced by their remarkable recyclability and stability under simulated harsh conditions, demonstrates great potential for large-scale oil spill cleanup operations.