(532a) How Reliable Are Isotherm Measurements in Metal-Organic Frameworks?

Metal-organic frameworks (MOFs) are a class of crystalline porous materials which are of interest for adsorption applications. The high level of interest in these materials has resulted in the collection of many gas adsorption isotherms in many MOFs via both experimental measurements and computational simulations. These adsorption isotherms, however, are often reported without any standard metric to identify how reliable or reproducible they are. Therefore, discussion of precision or deviations between independently measured gas adsorption isotherms within MOFs has been uncommon in the adsorption community. Without a standard of comparison for MOF materials, there are cases where previously reported adsorption properties are not in qualitative agreement with newly reported data – a point which often goes unaddressed. It raises a fundamental question about how reliable gas adsorption measurements can be in MOFs at similar adsorption conditions and how we as a community should quantify agreement in adsorption behavior. Our work presents a meta-anlyasis of experimental CO₂ adsorption isotherms in numerous MOFs via the NIST/ARPA-E Adsorption Database. We have devised an adsorbate- and adsorbent-independent algorithmic procedure to quantify the reliability of CO₂ adsorption in a collection of MOFs at specific adsorption conditions. Our systematic assessment evaluates the level of agreement between existing adsorption isotherms, even in the absence of an absolute reference adsorption isotherm, by means of hierarchical statistical methods. Through this work, we have probed the state of our collective knowledge about adsorption in MOFs and identified MOF/adsorbate pairs of reliable comparison as well as pairs where no such consensus yet exists.