(219d) Pore Structure Characterization of MOF-Based Materials By Gas Adsorption

Adsorption of test adsorbates, such as N₂, Ar and CO₂, is the most practical method for pore structure characterization of MOF-based materials, which in many cases display composite hierarchical structures. The pore size distribution analysis is commonly based on conventional NLDFT or QSDFT methods developed for carbon and silica microporous solids. The kernels of references isotherms employed in these methods do not take into account the specifics of MOF pore morphologies, which differ significantly from one MOF family to another. In some cases, application of these methods provides reasonable agreement with the crystallographic pore dimensions, however, in many cases the discrepancies are striking. To remedy this situation, we develop dedicated kernels of reference “fingerprint” isotherms capable of distinguishing between different MOF structures and access the defects, inter-crystalline pores, and secondary micro-mesopore structures of binding materials. The fingerprint isotherms are built from MC simulated isotherms verified by experiments on ideal non-defective MOF crystals. The efficiency of the proposed approach is demonstrated by drawing on the example of Cu-BTC composites.