Designing Internal Hierarchical Porous Networks in Polymer Monoliths that Exhibit Rapid Removal and Photocatalytic Degradation of Aromatic Pollutants

This paper describes the preparation of 3D polymer monoliths containing internal hierarchical porosity. The porous networks are fabricated based on Pickering high-internal-phase emulsions (HIPEs) stabilized by microporous β-cyclodextrin-based polymer particles (CDPs) as the emulsifier; CDPs are facilely synthesized by the polyaddition reactions without the need for catalysts. The designed Pickering agents enable to form a bicontinuous internal phase in 8:2 cyclohexane–water v/v, and the oil droplets in the continuous water phase is found to be fairly stable up to 1 month. Furthermore, the addition of acrylamide and N,N'-methylenebis(acrylamide) results in polymer networks after in situ thermal polymerization at 60 °C in the water phase, and the monoliths include both interconnected macropores from the HIPE template and micro- and mesopores from the CDPs embedded at the interface. The porous monoliths rapidly absorb a variety of solvents taking advantage of multiscale porosity and amphiphilicity. Furthermore, the materials can be efficiently used for the removal of aromatic pollutants and then reused after washing and drying without the deterioration of performance. Also, they exhibit high photocatalytic capability and good recyclability as being used as a catalytic support when embedded with titanium dioxide (TiO₂).