Water Adsorption on MOFs Studied by NMR Relaxometry.
The 5th International Simposium om Innovative Materials and Processes in Energy Systems
20-23 Oct 2019
|| Pizzanelli Silvia
, Freni Angelo
, Gordeeva Larisa Gennadievna
, Forte Claudia
Istituto di Chimica dei Composti OrganoMetallici
Boreskov Institute of Catalysis SB RAS
The development of effective and stable Metal-organic frameworks (MOFs) for adsorption heat
transformation (AHT) and heat storage is a major trend of research in the field . MOFs are microporous
materials made of metal ions and organic linkers that create an open crystalline structure, offering high
porosity, large surface area and adjustable ad/desorption behavior . Among various MOFs, NH2-MIL-125,
with specific surface area ≈ 1300 m2/g and micro-pore volume ≈ 0.56 cm3/g, is considered one of the most
promising MOF materials for heat transformation purposes [3,4]. The water adsorption isotherms
demonstrated that this compound offers free openings, can adsorb a large amount of water (up to 0.42 g/g)
and exhibits S-shaped isotherms , which is convenient for practical use in AHT cycles .
In the present paper, NH2-MIL-125 was synthesized according to the procedure described in the
literature  and its interaction with water was thoroughly investigated by solid state Nuclear Magnetic
Resonance (NMR) spectroscopy and Fast Field Cycling (FFC) relaxometry. With this aim, several MOF
samples were prepared with different levels of hydration, ranging from 0.04 g/g (corresponding to few water
molecules adsorbed on the surface of the pores) to 0.45 g/g (i.e., water filling the pores).