A compressible mesoporous SiO2 sponge supported by a carbon nanotube network

Abstract

Applications of mesoporous silica (m-SiO₂) have suffered from its fragility (monolithic m-SiO₂ easily collapses under compression) and limited internal molecular exchange through small channels. Previously reported hierarchical porous m-SiO₂ structures containing interconnected macropores could improve adsorption properties, but they were still intrinsically fragile without sufficient mechanical strength to sustain deformation. Here, we embed a three-dimensional carbon nanotube (CNT) skeleton into m-SiO₂ to fabricate bulk, robust sponges that can be compressed to large strains (60% volume reduction) repeatedly in both air and water. This is done by directly casting a uniform m-SiO₂ layer with tunable thickness onto the surface of CNTs while maintaining the original network and open porous structure, resulting in a core–shell CNT@m-SiO₂ hybrid sponge. By pumping fluid through the CNT@m-SiO₂ sponges under cyclic compression, the adsorption rate and efficiency of dye molecules can be significantly enhanced due to the mesoporous coating on CNTs and enhanced fluid exchange throughout internal pores. The CNT@m-SiO₂ sponges may be used as robust and flexible adsorption media, and chemical and biological sensors with high performance.