Tag Archives: zeolites

New design strategy for synthesizing metal-organic frameworks (MOFs)

A Jan. 24, 2017 news item on Nanowerk announces new research from South Korea,

The accurate interpretation of particle sizes and shapes in nanoporus materials is essential to understanding and optimizing the performance of porous materials used in many important existing and potentially new applications. However, only a few experimental techniques have been developed for this purpose.

A team of researchers, led by Professor Wonyoung Choe of Natural Science and Professor Ja Hun Kwak of Energy and Chemical Engineering [ at Ulsan National Institute of Science and Technology {UNIST}] has recently developed a novel design strategy for synthesizing various forms of functional materials, especially for metal-organic materials (MOMs).

The research team expects that this synthetic approach might open up a new direction for the development of diverse forms in MOMs, with highly advanced areas such as sequential drug delivery/release and heterogeneous cascade catalysis targeted in the foreseeable future.

A Jan. 6, 2017 UNIST press release, which originated the news item, provides more detail,

In the last decades, much research has been developed to the synthesis and design of functional materials, but only a few of them could control the walls of the interior of the particles within the nanoporous materials.

In the study, Professor Choe and his team denomstrated sequential self-assembly strategy for synthesizing various forms of MOM crystals, including double-shell hollow MOMs, based on single-crystal to single-crystal transformation from MOP to MOF.

Schematic representation of various forms of micro-/nanostructures. From left are Solid, core-shell, hollow, matryoshka, yolk-shell and multi-shell hollow structures.

Porous materials are highly utilized as catalysts or gas capture materials because they supply abundant surface active sites for chemical reaction. Although materials, like Zeolites, which can be obtained from nature, have the ability to act as catalysts for chemical reactions, they suffer from the difficulty of controlling pore sizes and shapes.

As one solution, scientists have developed self-assembled porous materials using organic molecules and metals. Metal-Organic Frameworks (MOFs) and Metal-Organic Polyhedral (MOPs) are notable examples and they both have holes all over their surfaces. MOPs dissolve easily in chemical solvent, while MOFs are practically insoluble.

“MOFs take the form of three-dimensional (3D) structure, linking metals with organic molecules, while MOPs agglomerate together to form larger clusters,” says Jiyoung Lee, the first contributor of the study and a graduate student in the combined master-doctoral program from Chemistry department.

Schematic illustration of form evolution.

Schematic illustration of form evolution.

According to the research team, this synthetic strategy also yields other forms, such as solid, core-shell, double and triple matryoshka, and single-shell hollow MOMs, thereby exhibiting form evolution in MOMs.

“The best feature of this technique is that it allows two very different substances to coexist within a single crystal,” says Professor Choe. “This technique also permits greater control over size and shape of the pore, which can be then used to regulate the entrance and exit of molecules.”

This particular synthetic approach also has the potential to generate new type of porous materials containing micropores with diameters less than 2nm, macropores with diameters between 20 to 50nm, as well as pores of larger than 50 nm. Such hierarchical pore structure plays a critical role during catalysis, adsorption, and separation processes.

Here’s a link to and a citation for the paper,

Evolution of form in metal–organic frameworks by Jiyoung Lee, Ja Hun Kwak & Wonyoung Choe. Nature Communications 8, Article number: 14070 (2017) doi:10.1038/ncomms14070 Published online: 04 January 2017

This is an open access paper.

Smart nanofibers could make kidney dialysis machines obsolete

Kidney dialysis machines may become obsolete with the development of a specialized composite. From a March 4, 2014 news item on Nanowerk,

A simple way to treat kidney failure. A new technique for purifying blood using a nanofiber mesh could prove useful as a cheap, wearable alternative to kidney dialysis.

Kidney failure results in a build up of toxins and excess waste in the body. Dialysis is the most common treatment, performed daily either at home or in hospital. However, dialysis machines require electricity and careful maintenance, and are therefore more readily available in developed countries than poorer nations. Around one million people die each year worldwide from potentially preventable end-stage renal disease.

In addition to this, in the aftermath of disasters such as the Japanese earthquake and tsunami of 2011, dialysis patients are frequently left without treatment until normal hospital services are resumed. …

The March 4, 2014 International Center for Materials Nanoarchitectonics (MANA) research highlight, which originated the news item, describes the work in detail,

… Mitsuhiro Ebara and co-workers at the International Center for Materials Nanoarchitectonics, National Institute for Materials Science in Ibaraki, Japan, have developed a way of removing toxins and waste from blood using a cheap, easy-to-produce nanofiber mesh1. The mesh could be incorporated into a blood purification product small enough to be worn on a patient’s arm, reducing the need for expensive, time-consuming dialysis.

The team made their nanofiber mesh using two components: a blood-compatible primary matrix polymer made from polyethylene-co-vinyl alchohol, or EVOH, and several different forms of zeolites – naturally occurring aluminosilicates. Zeolites have microporous structures capable of adsorbing toxins such as creatinine from blood.

The researchers generated the mesh using a versatile and cost-effective process called electrospinning – using an electrical charge to draw fibers from a liquid. Ebara and his team found that the silicon-aluminum ratio within the zeolites is critical to creatinine adsorption. Beta type 940-HOA zeolite had the highest capacity for toxin adsorption, and shows potential for a final blood purification product.
Although the new design is still in its early stages and not yet ready for production, Ebara and his team are confident that a product based on their nanofiber mesh will soon be a feasible, compact and cheap alternative to dialysis for kidney failure patients across the world.

The word “soon” may not mean the same thing to the research team as it does to a patient using kidney dialysis machines and, unfortunately, the researchers don’t offer specifics as to when this mesh might be available.

Here’s a link to and a citation for the researchers’ paper,

Fabrication of zeolite–polymer composite nanofibers for removal of uremic toxins from kidney failure patients by Koki Namekawa, Makoto Tokoro Schreiber, Takao Aoyagi and Mitsuhiro Ebara.  Biomater. Sci., 2014, Advance Article DOI: 10.1039/C3BM60263J First published online 31 Jan 2014

It is an open access paper although you will need to ‘log in’ in some fashion.