The new nanosheets grow in a uniform shape making it much easier to make the membranes used in chemical purification.
The new nanosheets grow in a uniform shape making it much easier to make the membranes used in chemical purification.

VIDEO: The one-step process for growing zeolite nanosheets.


The University of Minnesota-led team has developed a one-step, crystal growth process for making zeolite nanosheets (ultra-thin layers of material with molecular-sized pores) and demonstrated their use by making ultra-selective membranes for chemical separations.

These new membranes can separate individual molecules based on shape and size, which could improve the energy efficiency of chemical separation methods used to make everything from fuels to chemicals and pharmaceuticals.

The researchers have filed a provisional patent on the technology.

“Overall, we’ve developed a process for zeolite nanosheet crystal growth that is faster, simpler, and yields better quality nanosheets than ever before,” claims Michael Tsapatsis, a University of Minnesota chemical engineering and materials science professor and lead researcher on the study.

“Our discovery is another step toward improved energy efficiency in the chemical and petrochemical industries.”

High separation values

Today, most chemical and petrochemical purification processes are based on heat-driven processes like distillation. These processes are very energy intensive. For example, chemical separations based on distillation represent nearly 5% of the total energy consumption in the United States.

Several companies and researchers are developing more energy-efficient separations based on membranes that can separate molecules based on size and shape. One class of these membranes is based on zeolites, silicate crystals that have pores of molecular dimensions. However, the multi-step processes required for their manufacture are costly and difficult to scale up, and commercial production remains a challenge.

In this new discovery, researchers claim to have developed the first ever, bottom-up process for direct growth of zeolite nanosheets. These nanosheets can be used to make high quality molecular sieve membranes. The new material is only about five nanometers in thickness and several micrometers wide (10 times wider than previous zeolite nanosheets). The new nanosheets also grow in a uniform shape making it much easier to make the membranes used in chemical purification.

“With our new material it's like tiling a floor with large, uniform tiles compared to small, irregular chips of tile we used to have,” reports Mi Young Jeon, a University of Minnesota chemical engineering and materials science PhD graduate and the first author of the study.

“Uniform-shaped zeolite nanosheets make a much higher-quality membrane with surprisingly high separation values that can sieve-out impurities.”

Molecular dynamics calculations indicate that separation values in excess of 10000 may be achieved with these nanosheets.

The research has been published in the journal Nature.