NSF Nanoscale Science and Engineering Grantees Conference, Dec 3-5, 20058

Grant # : 0707610

NANO HIGHLIGHT

Precise Building Blocks for Hierarchical Nanomanufacturing of Membranes with Molecular Resolution

NSF NIRT Grant CMMI-0707610

PIs: Michael Tsapatsis, Marc Hillmyer, Alon V. McCormick, R. Lee Penn, Andreas Stein

Department of Chemical Engineering and Materials Science and Department of Chemistry, University of Minnesota, Minneapolis, MN


Zeolites are microporous materials that find numerous applications in catalysis, separations, ion exchange, etc. They have pores of the order of 1nm and can discriminate molecules based on size and shape. However, because of this small pore size they also exhibit mass transfer limitations (diffusion of molecules is slow).

The combination of ordered microporosity and mesoporosity is a possible solution in order to obtain materials that exhibit the molecular sieving properties of zeolites without the mass transfer limitations. An analogy would be that of freeways and streets, with the mesopores being freeways and the zeolite micropores being the streets. All the action takes place at the streets. However, in the absence of freeways, access to the streets and the corresponding action may be difficult. Therefore, numerous efforts in the last 15 years are aiming in this direction.

Recently published work1 form this team shows that ordered mico-meso-porous materials can be made by growing zeolite crystals in an ordered porous carbon scaffold (see schematic). After the zeolite is grown, the scaffold can be removed to generate larger highly interconnected pores precisely located to allow for fast transport of molecules to the molecular sieving areas. It is expected that these three dimensionally ordered mesoporous (3DOm) zeolites will exhibit faster reaction rates for reactions involving molecules that diffuse slowly in the zeolite pores.

The team demonstrated not only the imprinting of ordered mesoporosity, but also the synthesis, under appropriate conditions, of single isolated nanocrystals bearing size and shape perfection as well as unusual morphologies that cannot be accomplished otherwise. These precisely shaped zeolite nanoparticles can be used to form coatings for molecular sieve membrane applications.

Reference

W. Fan, M. Snyder, S. Kumar, P.-S. Lee, W.C. Yoo, A.V. McCormick, R.L. Penn, A. Stein and M. Tsapatsis, Nature Materials, Published Online, DOI:10.1038/nmat2302

For more information link to: http://www.cems.umn.edu/research/tsapatsis/NIRT_ZGCS/index.php or

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