The co-micelle/emulsion templating route to tailor nano-engineered hierarchically porous macrospheres

Here we present a new class of nano-engineered hierarchically porous materials in which the entire framework is mesoporous. This material is engineered into macrospheres of controllable size with a highly interconnected macropore network to facilitate molecular diffusion access. To achieve this, a new co-micelle/emulsion templating (co-MET) technique was developed. In this technique a block copolymer plays the dual roles of emulsion stabilization and micelle formation within the aqueous phase of that emulsion to produce the hierarchical structures. The emulsion templating provides the macroporous structure while the mesoporous structure is formed by hydrolyzation of silica around block copolymer micelles. Increasing the copolymer concentration improves the mesoporosity up to a certain concentration where the emulsion phase behavior changes and the macroporosity is affected. Unlike other hierarchically porous materials, the walls of the co-MET macrospheres are entirely mesoporous, which provides high surface areas (>500 m2 g−1) and pore volumes (>1 cm3 g−1) and narrow mesopore size distributions (∼10 nm). This interconnected hierarchical meso/macroporous structure combined with the controlled particle size makes this new class of materials promising for applications requiring high diffusion and throughput rates, alleviating the problems of using typical fine particle mesoporous materials.

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► Simultaneous templating on micelles and emulsion droplets.
► Independent control of particle size and porosity.
► Hieracrchical macro- and meso-porosity.
► Highly interconnected and tunable.