In situ Stöber templating: Facile synthesis of hollow mesoporous carbon spheres from silica-polymer composites for ultra-high level in-cavity adsorption

Hollow structuring of carbon materials with mesoporous walls has been shown to enhance performance in a range of adsorption-based applications. However, utilization of the in-cavity volume towards the maximum capacity offered by hollow nano-reservoirs is yet to be demonstrated. To achieve this goal, further development in the control of nanostructure in porous hollow carbons is paramount. Herein, we demonstrate a facile in situ Stöber templating approach for the synthesis of hollow mesoporous carbon spheres from silica/polydopamine composites. We present a conclusive mechanism for the assembly of such surfactant-free silica/polymer systems, based on the dynamic and controllable self-assembly between the silica core, silica primary particle and polymer precursors in a mixed Stöber system. We employ this new understanding for the generation of novel hollow mesoporous carbon spheres with tunable pore sizes, high pore volumes and controllable shell thicknesses tailored for high-level in-cavity adsorption. When used as an adsorbent for a wastewater pollutant di-(2-ethylhexyl)phthalate, our hollow mesoporous carbon spheres achieve an ultra-high adsorption capacity of 5084 mg g^-1, more than 10 times higher than previous reports. For the first time, we demonstrate that the cavity space offered by hollow structures can facilitate near-100% volumetric uptake in adsorption applications. These developments shed new light on the mechanism of silica-polymer composite assembly and the designed synthesis of functional nanoporous materials with versatile applications.