Browsing by Author "Feldmann, Wesley K."

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    Direct determination of enthalpies of sorption using pressure-gradient differential scanning calorimetry: CO2 sorption by Cu-HKUST
    (Wiley, 2020-06-01) Feldmann, Wesley K.; White, Kerry-Anne; Bezuidenhout, Charl X.; Smith, Vincent J.; Esterhuysen, Catharine; Barbour, Leonard J.
    Enthalpy of sorption (ΔH) is an important parameter for the design of separation processes using adsorptive materials. A pressure-ramped calorimetric method is described and tested for the direct determination of ΔH values. Combining a heatflow thermogram with a single sorption isotherm enables the determination of ΔH as a function of loading. The method is validated by studying CO2 sorption by the well-studied metal–organic framework Cu-HKUST over a temperature range of 288–318 K. The measured ΔH values compare well with previously reported data determined by using isosteric and calorimetric methods. The pressure-gradient differential scanning calorimetry (PGDSC) method produces reliable high-resolution results by direct measurement of the enthalpy changes during the sorption processes. Additionally, PGDSC is less labor-intensive and time-consuming than the isosteric method and offers detailed insight into how ΔH changes over a given loading range.
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    Pressure-gradient sorption calorimetry of flexible porous materials : implications for intrinsic thermal management
    (Wiley, 2020-08) Feldmann, Wesley K.; Esterhuysen, Catharine.; Barbour, Leonard J.
    Thermal management is an important consideration for applications that involve gas sorption by flexible porous materials. A pressure-gradient differential scanning calorimetric method was developed to measure the energetics of adsorption and desorption both directly and continuously. The method was applied to the uptake and release of CO2 by the well-known flexible metal–organic frameworks MIL-53(Al) and MOF-508b. High-resolution differential enthalpy plots and total integral enthalpy values for sorption allow comprehensive assessment of the thermal behavior of the materials throughout the entire sorption process. During adsorption, the investigated materials display the ability to offset exothermic adsorption enthalpy against endothermic structural transition enthalpy, and vice versa during desorption. The results show that flexible materials offer reduced total integral heat over a working range when compared to rigid materials.