Thermodynamics of hydrogen adsorption on metal-organic frameworks.
Interaction between adsorbed hydrogen and the coordinatively unsaturated Mg(2+) and Co(2+) cationic centres in Mg-MOF-74 and Co-MOF-74, respectively, was studied by means of variable-temperature infrared (VTIR) spectroscopy. Perturbation of the H(2) molecule by the cationic adsorbing centre renders the H--H stretching mode IR-active at 4088 and 4043 cm(-1) for Mg-MOF-74 and Co-MOF-74, respectively. Simultaneous measurement of integrated IR absorbance and hydrogen equilibrium pressure for spectra taken over the temperature range of 79-95 K allowed standard adsorption enthalpy and entropy to be determined. Mg-MOF-74 showed ΔH(0)=-9.4 kJ mol(-1) and ΔS(0)=-120 J mol(-1) K(-1), whereas for Co-MOF-74 the corresponding values of ΔH(0)=-11.2 kJ mol(-1) and ΔS(0)=-130 J mol(-1) K(-1) were obtained. The observed positive correlation between standard adsorption enthalpy and entropy is discussed in the broader context of corresponding data for hydrogen adsorption on cation-exchanged zeolites, with a focus on the resulting implications for hydrogen storage and delivering.
Areán
Carlos O
CO
Department of Inorganic, Physical and Material Chemistry, NIS Center of Excellence and INSTM Unità di Torino, University of Torino, 10135 Torino, Italy.
Chavan
Sachin
S
Cabello
Carlos P
CP
Garrone
Edoardo
E
Palomino
Gemma T
GT