Direct ink writing of hierarchically porous MOF@carbon monoliths for Joule heating assisted carbon capture

In the last decades, metal-organic frameworks (MOFs) have emerged as promising adsorbents in fields like atmospheric water harvesting and carbon capture. Despite their excellent sorption performance, most MOFs have yet to make their way from research laboratories into industrial processes. A big hurdle for the industrial application of MOFs is their microcrystalline nature, which leads to processing issues and high pressure drops in flow-based systems. In this study, we present a direct ink writing based 3D printing approach that combines MOF powders with carbons to produce hierarchically porous electrically conductive monolithic MOF@carbon composites with a tunable shape. Two MOFs, namely CAU-10-H and CALF-20 were combined with graphite and activated carbon (AC) respectively, to yield CAU-10@graphite and CALF-20@AC monoliths with quadratic macropore channels. The monoliths have a size of ca. 30 x 30 × 50 mm 3 with high MOF loadings of 47.2 wt %. PXRD and sorption analysis showed, that the microporosity and crystallinity of both MOFs remained intact after the 3D printing process. Investigations of their CO 2 adsorption capacity using static and dynamic methods resulted in uptake values of 0.5 and 1.4 mmol/g at 25 °C and 0.3 bar CO 2 partial pressure for CAU-10@graphite and CALF-20@AC, respectively. Joule heating was used to internally heat the monoliths to over 60 °C, reducing the CO 2 desorption time by up to a third.