Highly Selective Water Adsorption in a Lanthanum Metal-Organic Framework

• Published in: Chemistry : a European journal Vol. 20; no. 26; pp. 7922 - 7925
• Main Authors: Plessius, Raoul, Kromhout, Rosa, Ramos , André Luis Dantas, Ferbinteanu, Marilena, Mittelmeijer-Hazeleger, Marjo C., Krishna, Rajamani, Rothenberg, Gadi, Tanase, Stefania
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 23.06.2014; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Subjects: Adsorption; Alcohols; Channels; Chemistry; desiccant; Desiccants; Diffraction; lanthanides; Lanthanum; Metal-organic frameworks; Metalorganic compounds; Methyl alcohol; Water chemistry; adsorption; desiccant; lanthanides; metal-organic frameworks
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201403241

We present a new metal–organic framework (MOF) built from lanthanum and pyrazine‐2,5‐dicarboxylate (pyzdc) ions. This MOF, [La(pyzdc)1.5(H2O)2]⋅2 H2O, is microporous, with 1D channels that easily accommodate water molecules. Its framework is highly robust to dehydration/hydration cycles. Unusually for a MOF, it also features a high hydrothermal stability. This makes it an ideal candidate for air drying as well as for separating water/alcohol mixtures. The ability of the activated MOF to adsorb water selectively was evaluated by means of thermogravimetric analysis, powder and single‐crystal X‐ray diffraction and adsorption studies, indicating a maximum uptake of 1.2 mmol g−1 MOF. These results are in agreement with the microporous structure, which permits only water molecules to enter the channels (alcohols, including methanol, are simply too large). Transient breakthrough simulations using water/methanol mixtures confirm that such mixtures can be separated cleanly using this new MOF. Soak up the water: A new lanthanide MOF, [La(pyzdc)1.5(H2O)2]⋅2 H2O (pyzdc=pyrazine‐2,5‐dicarboxylate), is thermally and hydrothermally stable at high temperatures. It has hydrophilic 1D tetragonal channels with a window size of about 3.8×3.5 Å, just large enough for water molecules, and shows highly selective water adsorption. It opens exciting opportunities for developing new desiccants for removing small amounts of water from water/alcohol mixtures and wet gases (see figure).