Isothermal Titration Calorimetry to Investigate Uremic Toxins Adsorbing onto Metal-Organic Frameworks

Summary Recent efforts have examined metal-organic frameworks (MOFs) as sorbents for removing pollutants and trace chemicals, such as pharmaceuticals, from aqueous media. To date, few studies have investigated the energetics of interactions between toxic species and MOF-based sorbents. To this end, we elected to use isothermal titration calorimetry (ITC) to quantify the thermodynamic parameters associated with the adsorption of uremic toxins, namely p-cresyl sulfate and indoxyl sulfate, onto zirconium-based MOFs. NU-1000, a mesoporous MOF comprising a pyrene-based linker, possesses two distinct adsorption sites that display dramatically different enthalpic and entropic parameters. ITC measurements further reveal that a concerted interaction that embodies both favorable enthalpic and entropic contributions is critical for designing a high-capacity MOF-based adsorbent.