Metal-organic frameworks (MOFs) have shown promising performance in separation, adsorption, reaction, and storage of various industrial gases; however, their large-scale applications have been hampered by the lack of a proper strategy to formulate them into scalable gas-solid contactors. Herein, we report the fabrication of MOF monoliths using the 3D printing technique and evaluation of their adsorptive performance in CO removal from air. The 3D-printed MOF-74(Ni) and UTSA-16(Co) monoliths with MOF loadings as high as 80 and 85 wt %, respectively, were developed, and their physical and structural properties were characterized and compared with those of MOF powders. Our adsorption experiments showed that, upon exposure to 5000 ppm (0.5%) CO at 25 °C, the MOF-74(Ni) and UTSA-16(Co) monoliths can adsorb CO with uptake capacities of 1.35 and 1.31 mmol/g, respectively, which are 79% and 87% of the capacities of their MOF analogues under the same conditions. Furthermore, a stable performance was obtained for self-standing 3D-printed monolithic structures with relatively good adsorption kinetics. The preliminary findings reported in this investigation highlight the advantage of the robocasting (3D printing) technique for shaping MOF materials into practical configurations that are suitable for various gas separation applications.

Structured adsorbents, especially in the form of monolithic contactors, offer an excellent gas-solid contacting strategy for the development of practical and scalable CO capture technologies. In this study, the fabrication of three-dimensional (3D)-printed 13X and 5A zeolite monoliths with novel structures and their use in CO removal from air are reported. The physical and structural properties of these printed monoliths are evaluated and compared with their powder counterparts. Our results indicate that 3D-printed monoliths with zeolite loadings as high as 90 wt % exhibit adsorption uptake that is comparable to that of powder sorbents. The adsorption capacities of 5A and 13X monoliths were found to be 1.59 and 1.60 mmol/g, respectively, using 5000 ppm (0.5%) CO in nitrogen at room temperature. The dynamic CO/N breakthrough experiments show relatively fast dynamics for monolithic structures. In addition, the printed zeolite monoliths show reasonably good mechanical stability that can eventually prevent attrition and dusting issues commonly encountered in traditional pellets and beads packing systems. The 3D printing technique offers an alternative, cost-effective, and facile approach to fabricate structured adsorbents with tunable structural, chemical, and mechanical properties for use in gas separation processes.

Porous solids in the form of adsorbents and catalysts play a crucial role in various industrially important chemical, energy, and environmental processes. Formulating them into structured configurations is a key step toward their scale up and successful implementation at the industrial level. Additive manufacturing, also known as 3D printing, has emerged as an invaluable platform for shape engineering porous solids and fabricating scalable configurations for use in a wide variety of separation and reaction applications. However, formulating porous materials into self-standing configurations can dramatically affect their performance and consequently the efficiency of the process wherein they operate. Toward this end, various research groups around the world have investigated the formulation of porous adsorbents and catalysts into structured scaffolds with complex geometries that not only exhibit comparable or improved performance to that of their powder parents but also address the pressure drop and attrition issues of traditional configurations. In this comprehensive review, we summarize the recent advances and current challenges in the field of adsorption and catalysis to better guide the future directions in shape engineering solid materials with a better control on composition, structure, and properties of 3D-printed adsorbents and catalysts.

Amine-based materials have represented themselves as a promising class of CO adsorbents; however, their large-scale implementation requires their formulation into suitable structures. In this study, we report formulation of aminosilica adsorbents into monolithic structures through a three-dimensional (3D) printing technique. In particular, 3D-printed monoliths were fabricated using presynthesized silica-supported tetraethylenepentamine (TEPA) and poly(ethylenimine) (PEI) adsorbents using three different approaches. In addition, a 3D-printed bare silica monolith was prepared and post-functionalized with 3-aminopropyltrimethoxysilane (APS). Characterization of the obtained monoliths indicated that aminosilica materials retained their characteristics after being extruded into 3D-printed configurations. Adsorptive performance of amine-based structured adsorbents was also investigated in CO capture. Our results indicated that aminosilica materials retain their structural, physical, and chemical properties in the monoliths. In addition, the aminosilica monoliths exhibited adsorptive characteristics comparable to their corresponding powders. This work highlights the importance of adsorbent materials formulations into practical contactors such as monoliths, as the scalabale technology platform, that could facilitate rapid deployment of adsorption-based CO capture processes on commercial scales.

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