MOFs functionalization of 3D printed mullite complex architectures for CO2 capture

Anthropogenic emissions of green-house gases and increasing CO2 atmospheric concentration are considered the major causes of global warming and ocean acidification. Carbon capture and sequestration turned out to be a valuable strategy to help mitigating these problems, making it urgent to develop novel materials able to selectively capture CO2. Thus, in the present experimental study, a new system for CO2 capture based on porous mullite (3Al2O3⋅2SiO2) substrates fabricated by Digital Light Processing and properly functionalized with Metal Organic Frameworks (MOFs) was developed. Printable ceramic pastes were obtained by mixing in proper amounts commercial mullite powders to a photocurable commercial resin with a dispersant and a sintering additive to optimize the rheological behaviour, printability, and solid loading. Then, different geometries were successfully shaped with high accuracy: bars, pellets, as well as monoliths with two structures, grid-like and Schwartz primitive triply periodic minimal surface (TPMS). After debinding and sintering of the samples, mullite substrates were successfully functionalized with HKUST-1 (Cu3(BTC)2) crystals by a two-step solvothermal synthesis process. HKUST-1 powders, as well as blank and coated lattice monoliths were tested in a catalytic bench reactor under 1% CO2 flux (99% He). Before each measurement samples were heated at 120 °C for 4 h under He flux for regeneration. The samples showed an efficient CO2 adsorption capacity, and the regeneration efficiency led to reusable and durable systems. Preliminary results showed that the TPMS structure was a more efficient substrate than grid-like architecture for capturing CO2, because of its higher surface area. Thus, this study demonstrates how the combination between additive manufacturing and MOFs technologies can set the stage to produce efficient engineered systems for CO2 capture.