Animated organic-inorganic hybrid materials and their use as catalyst scaffolds

For the past two decades, organic-inorganic hybrids (OIHs) have been researched extensively and tailored in a facile manner to suit a wide variety of applications due to their highly functional and tunable nature. The molecular scale mixing of the organic and inorganic components imparts unique properties to these materials. Stimuli-responsiveness or animated nature is one such property, resulting from the non-covalent interactions of the organic groups present in close proximity with the inorganic (-Si-O-Si-) framework. In this article, we provide a comprehensive review of the animated silica-based OIHs synthesized by sol-gel technique. The earlier sections of the review focus on the development and synthesis of animated materials derived from bis-[3-(trimethoxysilyl) propyl] ethylenediamine (enTMOS) and bis-trimethoxysilylethyl benzene (BTEB). Their response to stimuli and the principles governing their animated nature along with the effect of synthesis parameters on their properties have been discussed. The latter portion of the article offers a detailed overview of the application of swellable organically modified silica (SOMS) supported Pd catalysts for aqueous phase hydrodechlorination of the toxic organic contaminant, trichloroethylene, which is commonly found in groundwater. The affinity of SOMS to organics and its ability to swell and adsorb organics from aqueous solutions impacted the accessibility of the active Pd sites and imparted resistance to deactivation against anionic species encountered in groundwater. Finally, other catalytic applications of SOMS and an outlook on the future research avenues and applications of SOMS have been presented.