A MS-16 micro reactor was loaded with 48.3 grams of the TCMCFL sample, and the reactor was coupled with a custom high-pressure PCT system capable of measurements up to approximately 1000 bar (see Supplementary Information for additional details). The reactor was leak checked, calibrated, and then the sample was activated at 200 • C in vacuum. An initial set of isotherms were measured (Figure ), that demonstrate the promise of this material for high pressure compression applications. The material exhibits a reasonably flat plateau at 20 • C and minimal hysteresis, achieving an absorption capacity of 1.5 wt% at a pressure of 400 bar. Accessing the full plateau at 151 • C would exceed the pressure limitations of the PCT machine (>1000 bar), but we observe a capacity of 0.5 wt% at a desorption pressure of 875 bar. Therefore, as much as 1.0 wt% can be compressed from 400 to 875 bar via a 20 ↔ 151 • C temperature swing. At a reduced desorption temperature of 103 • C, 0.7 wt% could be pressurized from 400 to 750 bar. This material also maintains a long shelf-life, with no major change observed in the PCT isotherm after 12 months maintained under inert atmosphere. Taken 12 months after Figure , Figure shows additional PCT measurements at additional temperatures for performing the van't Hoff analysis (using fugacity, f , instead of pressure ) in Figure . The observed value of ∆H d = 14.1 kJ mol -1 indeed represents a 2.5 kJ mol -1 decrease compared to the base TCMFL and is qualitatively consistent with the expected decrease according Table . However, the observed value ∆S d = 95.8 J mol -1 K -1 represents an accompanying decrease of 8.4 J mol -1 K -1 in the desorption entropy compared to the base TCMFL. This enthalpy-entropy compensation is common in materials design, and often limits the extent to which one can freely tune the free energy of the hydriding reaction by modulating ∆H. Systems-level modeling of high-pressure compressor operation. To show the potential for the TCMCFL material in a realistic compressor application, a systemlevel dynamic model of a metal hydride-based compressor was used to predict 2-stage and 3-stage compressor performance using the TCMCFL hydride for the high-pressure stage. Such modeling has been performed by others to take into account the complex process involving chemical kinetics and thermodynamics coupled with heat and mass transfer as multiple metal hydride beds undergo synchronized hydrogen absorption and desorption in a realistic system geometry. Here we use a model developed at Sandia using Matlab products Simulink and Simscape and described in detail elsewhere and summarized in the SI.