Polymer-derived ceramics produced by vat photopolymerization deliver a novel way to create complex monolithic structures with hierarchical porosity. In this work, polysiloxane-derived silicon oxycarbides (SiOCs) are combined with a sacrificial monomer and shaped via vat photopolymerization, during which a photopolymerization-induced phase separation occurs. Through subsequent pyrolysis, ceramic SiOC materials can be obtained. The obtained hierarchical porosity can be functionalized to clear wastewater from organic dyes or heavy metals.

By choice of polysiloxane compounds of different carbon content, maximum pyrolysis temperature, and complexity of the monolith geometry, functionalities of the ceramic like hydrophilicity, pore size, permeability, and carbon content can be manipulated. These characteristics can be adjusted to suit applications such as wastewater purification. Here, the functional group of polysiloxanes was varied between a phenyl-/methyl group, to manipulate the amount of carbon introduced into the system. The pyrolysis temperature was varied between 600-800 °C, whereby the polymer-to-ceramic conversion is only fully completed at the high end of the temperature range. In terms of part geometry, both simple cylinders and more complex scaffold structures could be fabricated. Methylene blue was chosen as adsorbent to observe the potential for water purification. The concentration of the dye was measured via UV-VIS spectroscopy.

With increasing pyrolysis temperatures exceeding, hydrophilicity of the surfaces as well as overall permeability were found to increase, while carbon content decreases. Pore size distribution was found to remain constant. By variation of different ratios of the polysiloxane derivates, carbon content could be controlled between 27 and 47 %, and the modal pore size ranged from 0.05 to 0.5 µm.

The system established in this work can be used to suit specific wastewater removal applications such as problematic organic or metal compounds and can be tailored to suit various complex spatial requirements via vat photopolymerization.