Hydrogen Surface Interactions in Pores

Theoretical and modelling studies of H2 adsorption on porous materials suggest that introduction of light, non-transition metal ions, for example 

While the isosteric enthalpy of adsorption values reported so far for hydrogen adsorption on porous materials are too low for significant adsorption at ambient temperatures, high values would make hydrogen desorption very difficult. An intermediate weak nondissociative coordination or other weak chemisorption with higher isosteric enthalpy of adsorption values with facile adsorption and desorption characteristics is required for storage applications. 

Direct evidence of hydrogen in pores has been provided by X-ray diffraction studies.f ° ° Takamizawa and Nakata observed dense aggregates of adsorbed hydrogen in MOF [Rh°(bza)4(pyz)] (where bza = benzoate and pyz = pyrazine) at 90 Hydrogen molecules adsorbed 

Six D2 adsorption sites were identified in HKUST-1 (Cu3(btc)2, where btc = 1,3,5-benzenetricarboxylate) using neutron powder diffraction methods. Initial adsorption occurred on the coordinatively unsaturated axial sites of the dinuclear Cu centre [CU-D2 = 2.39(1) This 

Studies of hydrogen adsorption on Cu3[Co(CN)6]2 using high-resolution neutron powder diffraction showed that at 1,2 and 2.3 H2/CU loadings, the hydrogen was absorbed on two sites. The strongest adsorption site was an interstitial location within the structure. The second adsorption site was associated with exposed Cu ion coordination sites that result from the presence of [ColCN) ] vacancies. 

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