Shaping SBA-15 particles into highly porous macro-mesoporous monoliths by digital light processing

This study presents a simple procedure to design macro-mesoporous monoliths using well-known SBA-15 particles mixed with a commercial photocurable resin and Disperbyk-103 as dispersant to form a printable slurry for digital light processing (DLP). SBA-15 mesoporous silica rods give their well-defined and well-ordered mesoporosity to the material, while DLP allows shaping the particles in a macroporous monolith, using as example the gyroid macroporosity. SBA-15 particles were characterised before printing using a combination of SEM, SAXS and N2 sorption to characterise their shape, mesopore organisation and mesopore volume respectively. Several formulations, with different concentrations of SBA-15 (15–18 wt%) with and without the presence of additives (non-porous silica particles or calcium oxide), were tested. Rheological studies proved all formulations to have a shear-thinning behaviour, and only formulations with a viscosity at printing shear below 5 Pa.s were used for printing. First printing proved most formulations could be printed, but only the formulation with CaO as sintering aids gives a material that withstand calcination at 1000°C. Finally, the most suited formulation (15 wt% of SBA-15 in the total mixture; with 5 wt% of Disperbyk-103 and 1 wt% of CaO compared to SBA-15) was used to print “dense” cylinders, exhibiting only the SBA-15 mesoporosity and “macroporous” cylinders with a gyroidal macroporosity. The samples withstand sintering up to 1000°C without loss of the mesoporous organisation or an alteration of the shape of SBA-15 particles composing the monolith. This work hence shows a simple procedure to valorise SBA-15 particles into monoliths with hierarchical porosity, with possible applications as adsorbents or filters.