Manufacturing of metal-organic framework monoliths and their application in CO₂ adsorption

An important class of novel mesoporous and microporous adsorbents like metal-organic frameworks (MOFs) are normally produced in powder form. This paper presents a generic method of manufacturing and characterisation of these materials into low pressure drop and energy saving monolithic structures for industrial applications. One of the MOF candidates that was considered in this study was MIL-101 (Cr) ([Cr₃O(OH)(H₂O)₂(bdc)₃].xH₂; bdc = 1,4-benzenedicarboxylate), and the model contaminant gas tested was carbon dioxide (CO₂). MIL-101 (Cr) monoliths were manufactured by paste extrusion techniques from the synthesized MIL-101 (Cr) powder. These MIL-101 (Cr) monoliths were then characterised using powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), radial compression tests and intelligent gravimetric analysis (IGA). Adsorption properties of the prepared MIL-101 (Cr) powder and monoliths were determined from their pure CO₂ sorption isotherms and dynamic adsorption breakthrough curves, that were carried out using high concentration (40% v/v) CO₂ challenge. Results have demonstrated that the resulting MIL-101 (Cr) monoliths were highly porous, mechanically strong on compressive loading, thermally regenerable with comparable CO₂ adsorption capacity to the synthesized MIL-101 (Cr) powder. From breakthrough curves, mass transfer characteristics such as mass transfer zone velocity and length of the prepared MIL-101 (Cr) monoliths have also been evaluated in this study.