Bachelor students tackle water-alcohol separation

New hybrid material published in top-tier chemistry journal

13 June 2014

Chemistry bachelor students Rosa Kromhout and Raoul Plessius have succeeded in crystallising a new hybrid porous material that can selectively adsorb water from water-alcohol mixtures. Their so-called metal-organic framework (MOF) is stable up to 400 degrees Celsius, making it an excellent candidate for application in real-life industrial separations. The research, led by Dr. Stefania Tanase Grecea of the Van 't Hoff Institute for Molecular Sciences, is part of the UvA Research Priority Area Sustainable Chemistry.

In the chemical industry separations are often more costly and more problematic than the actual chemical reactions. One of the important challenges is the separation of small amounts of water from alcohols, for which expensive and cumbersome distillation procedures are needed. Removing the last traces of water requires enormous distillation columns that consume large amounts of energy.

Now, two second-year chemistry students, Rosa Kromhout and Raoul Plessius succeeded in making and crystallising a new type of porous material that can efficiently dehydrate alcohols - without distillation.

Rosa Kromhout and Raoul Plessius

Rosa Kromhout (left) and Raoul Plessius. Photos: HCSC/HIMS

Their work, done during their four-week research project in the Heterogeneous Catalysis and Sustainable Chemistry group under the supervision of Dr Stefania Tanase Grecea and Prof. Gadi Rothenberg, has just been published as a communication in the highly respected journal 'Chemistry - A European Journal'. Plessius and Kromhout are first authors.

High-quality research

Photo of Stefania Grecea

Dr Stefania Tanase Grecea. Photograph: Roberto Calderone.

The publication shows that second-year UvA chemistry students are able to perform high-quality scientific work. Dr Grecea is proud of her pupils: 'MOF synthesis and crystallisation can be extremely frustrating. There is no guarantee that the material you want to make will actually crystallise. Rosa and Raoul worked diligently in the lab, trying literally hundreds of formulations. Finally they were rewarded with beautiful crystals'.

The experiments were complemented by advanced molecular simulations, run by Prof. Rajamani Krishna of the Computational Chemistry group, also part of the RPA Sustainable Chemistry. Krishna was able to confirm, using transient breakthrough simulations, that water-alcohol mixtures can be separated cleanly using the new MOFs.

Robust

The new lanthanide MOF is not only structurally beautiful but also highly unusual. It has a stable microporous structure with hydrophilic onedimensional tetragonal channels which are 'just right' for accommodating water molecules. Furthermore, the lanthanum ions, with their large coordination sphere and flexible coordination geometry, facilitate structural re-organization without disrupting the overall framework. This makes the porous framework highly robust, allowing multiple dehydration/hydration cycles. Unlike most MOFs, it is also hydrothermally stable at high temperatures. This makes it a realistic candidate for removing small amounts of water from water-alcohol mixtures as well as wet gases.

Grecea, Rothenberg and Krishna will continue developing this new family of materials for sustainable separations.

Lantanide based MOF for water-alcohol separation

Space-filling representation of the 3D structure of the lanthanum MOF showing the 1D channels where the water molecules are adsorbed. It is built from lanthanum cations and pyrazine-2,5-dicarboxylate anions. Illustration: HCSC/HIMS

Article

Highly selective water adsorption in a lanthanum metal-organic framework. R. Plessius, R. Kromhout, A.L. Dantas Ramos, M. Ferbinteanu, M.C. Mittelmeijer-Hazeleger, R. Krishna, G. Rothenberg and S. Tanase,Chem. Eur. J., 2014, EarlyView: DOI: 10.1002/chem.201403241

Published by  HIMS