Synchrotron based absorption edge tomography for the analysis of 3D printed polymer embedded MOF

Absorption edge tomography (AET), also known as differential tomography at absorption edges, is a method which exploits the sudden change of the attenuation coefficient, when the photon energy crosses the absorption edge of an element [1]. Synchrotron radiation is the best source for absorption edge tomography, because of its small bandwidth, high intensity and easily adjustable photon energy [2]. The synchrotron beamline BAMline at the synchrotron radiation facility BESSY II in Berlin, which is operated by the Bundesanstalt für Materialforschung und -prüfung (BAM), provides a monochromatized beam in a photon energy range from 5 keV up to 80 keV with a bandwidth of 2%, when the double multilayer monochromator is used [3]. Together with the microtomography setup, this enables differential tomography with submicron resolution at the K edge of the elements [4] from chromium up to the lanthanides, and up to uranium, when the L edges are used as well. In this work, mechanochemically synthesized metal-organic framework (MOF) material HKUST-1 in combination with acrylonitrile- butadiene styrene (ABS) polymer was used to form a polymer MOF composite material by a simple extruder. This composite filament was used for 3D printing. Absorption edge tomography facilitated the evaluation of the 3D distribution of the MOF material both in the filament and the resultant printed sample up to μm resolution. Our very first data indicate, that HKUST-1 is mainly homogeneously dispersed in both polymer bulk materials. In addition, a few clusters having significantly higher Cu concentration were found. AET in combination with data fusion also allows for the calculation of the MOF amount located on the external polymer surface.