3D-Printed ZnO/SiOC Gyroid Monoliths as Efficient Photocatalysts for Continuous-Flow Operation

The development of photocatalysts that combine structural robustness with geometrical tunability is pivotal for advancing sustainable water treatment technologies. Here, we report the design and fabrication of 3D-printed ZnO-functionalized SiOC ceramic monoliths for the efficient photodegradation of organic dyes under UV irradiation. The SiOC scaffolds were produced via the polymer-derived ceramics (PDCs) route coupled with Digital Light Processing (DLP) 3D printing, enabling precise control over three-dimensional geometry, pore interconnectivity, and mechanical integrity under flow conditions. ZnO nanoparticles were subsequently deposited by spray-coating, yielding a homogeneous catalytic surface layer while preserving the architecture of the printed monoliths. Structural and morphological analyses (SEM, TEM, XRD, XPS) confirmed the uniform anchoring of ∼10 nm ZnO nanoparticles onto the SiOC surface, forming a stable interface favorable for charge transfer. Photocatalytic activity was evaluated in a continuous-flow reactor using both cationic (methylene blue) and anionic (methyl orange) dyes as model pollutants. The ZnO/SiOC gyroid monolith achieved 90% MB degradation after 120 min, comparable to that of ZnO powder, while offering markedly superior stability and recyclability. After ten consecutive cycles, the monolithic catalyst maintained nearly constant photocatalytic activity, showing no significant loss in efficiency, whereas ZnO powder suffered ∼20% efficiency loss due to nanoparticle agglomeration and surface deactivation. These results demonstrate that integrating additive manufacturing with polymer-derived ceramics enables the engineering of durable, reactor-ready photocatalysts, paving the way toward scalable continuous-flow water treatment technologies.