Porosimetry of zeolitic imidazolate frameworks using positronium probe

Metal organic frameworks (MOF) are crystalline compounds composed of metal nodes and organic moiety. Zeoliticimidazolate framework (ZIF) is a subset of MOFs having high chemical and thermal stability. Due to high porosity, ZIFs are shown to have many applications in gas storage, catalysis, sensing, CO₂ capture, heavy metal removal and antibacterial property. Gas adsorption based methods are found to be incapable for determination of their average pore size and porosity due to the flexibility of these frameworks. Recently, it has been shown that positronium probe can efficiently be used to determine the average pore size of ZIFs without any artifact from flexibility of the frameworks. In addition, positronium diffusion measurements could provide the information about the interconnectivity of pore in the frameworks. In order to validate the efficiency of Ps probe for MOFs, we have carried out PALS measurements for a number of ZIFs having different pore architecture