High-pressure, ambient temperature hydrogen storage in metal-organic frameworks and porous carbon

We investigated hydrogen storage in micro-porous adsorbents at ambient temperature and pressures up to 320 bar. We measured three benchmark adsorbents: two metal-organic frameworks, Cu$_{\mathrm{3}}$(1,3,5-benzenetricarboxylate)$_{\mathrm{2}}$ [Cu$_{\mathrm{3}}$(btc)$_{\mathrm{2}}$; HKUST-1] and Zn$_{\mathrm{4}}$O(1,3,5-benzenetribenzoate)$_{\mathrm{2}}$ [Zn$_{\mathrm{4}}$O(btb)$_{\mathrm{2}}$; MOF-177], and the activated carbon MSC-30. In this talk, we focus on adsorption enthalpy calculations using a single adsorption isotherm. We use the differential form of the Claussius-Clapeyron equation applied to the Dubinin-Astakhov adsorption model to calculate adsorption enthalpies. Calculation of the adsorption enthalpy in this way gives a temperature independent enthalpy of 5-7 kJ/mol at the lowest coverage for the three materials investigated. Additionally, we discuss the assumptions and corrections that must be made when calculating adsorption isotherms at high-pressure and adsorption enthalpies.