High Pressure Amplifying Framework Materials for Programmable Pneumatics Systems

Negative Gas Adsorption (NGA), discovered in a series of mesoporous switchable MOFs, was hitherto regarded as a curios phenomenon occurring only at pressures well below or close to atmospheric merit. Herein we demonstrate mesoporous frameworks interacting with carbon dioxide, to show stimulated breathing transitions well above 100 kPa. Reversible CO₂ adsorption-induced switching was observed in DUT-46 (DUT = Dresden University of Technology), in contrast to irreversible transitions for DUT-49 and DUT-50, as demonstrated via synchrotron in situ PXRD/adsorption experiments. Systematic physisorption experiments reveal the best conditions for high pressure NGA transitions in the pressure range of 350 - 680 kPa. The stimulated framework contraction expells CO₂ in the range of 1.1 to 2.4 mmol g^-1 leading to autonomous pressure amplification in a closed system. In a pneumatic demonstrator system we achieved pressure amplification of 90 kPa at a high operating pressure of 340 kPa. According to system level estimations even higher theoretical pressure amplification may be achieved between 535 kPa and 1011 kPa for DUT-49 using CO₂ as a non-toxic and non-flammable working gas. Operable pressure ranges exceeding 100 kPa render pressure amplifying framework materials as realistic candidates for the integration into energy autonomous responsive pneumatic systems.