Résumé
3D printing has gained a lot of interest in material science for the fabrication of complex structures that could not be produced using conventional approaches. Among 3D printing techniques, digital light processing (DLP) allows for the rapid printing of monolithic structures with high freedom of design. Printed structures can be tailored to address specific needs, for instance through the implementation of complex and well controlled macroporous networks that are a critical requirement for in-flow applications involving the transport of a fluid throughout the material. In this context, we have developed a new approach for the direct DLP printing of mesoporous parts with high specific surface area based on 10 nm-sized porous silica nanocages functionalized with methacrylate ligands [1]. In this contribution, we will show how the printed material properties (specific surface area, resolution, composition) can be modulated through nano-ink formulation and printing parameters. This method results in low-organic content formulations that are compatible with commercial 3D printers, enabling the direct printing of hierarchically porous structures without any calcination step required. This intrinsic porosity is generating important opportunities for the implementation of functionalities either directly during printing or through post-printing treatments. For instance, a large variety of metallic sites can be integrated to the silica framework by adding the corresponding salt to the ink formulation. The resulting monoliths feature metallic sites supported on silica and are of high interest as catalytic reactors. The printed structures can also be infiltrated post-fabrication with a variety of precursors. With this approach, either new compounds can be formed within the silica structure or the silica itself can be used as a reactant to obtain a different material. This was demonstrated through the in-situ growth of MOF crystals within the silica scaffold, which added microporosity next to the macro-, mesoporosity of the printed structure. These MOF loaded monoliths exhibit enhanced specific surface area, as well as good CO2 sorption capacity. In another post-fabrication approach, the 3D printed structures of amorphous silica were converted into zeolitic materials through pseudomorphic transformation. During this reaction, the porous silica monolith is dissolved and recrystallized into a zeolite [2]. While the macroscopic shape of the 3D printed object is fully preserved, micropores are generated, effectively allowing for the manufacturing of zeolite monoliths with complex geometry and shapes. Carefully adjusting the conditions further enabled the selective synthesis of various pure phases, hence allowing for a fine control of the microporous network as well.The convergence of 3D printing with porous nanomaterials is hence generating important opportunities for the manufacturing of hybrid and hierarchical monoliths. This approach is perfectly well suited to design and make complex materials with high potential in environmental applications, such as carbon capture technologies and catalytic flow reactors.References[1] T. Aubert, J. Huang, K. Ma, T. Hanrath, U. Wiesner, Porous cage-derived nanomaterial inks for direct and internal three-dimensional printing, Nat. Commun. 2020, 11, 4695.[2] B. Said, T. Cacciaguerra, F. Tancret, F. Fajula, A. Galarneau, Size control of self-supported LTA zeolite nanoparticles monoliths, Micropor. Mesopor. Mat. 2016, 227, 176.