Iron oxide frameworks with hierarchical pore structure from pyrolysis of Prussian blue nanocrystals
Adsorption, catalysis, or substrates for tissue growth: porous materials have many potential applications. In the journal Angewandte Chemie, a team of Chinese and Australian researchers has now introduced a method for the synthesis of ultralight three-dimensional (3D) iron oxide frameworks with two different types of nanoscopic pores and tunable surface properties. This superparamagnetic material can be cut into arbitrary shapes and is suitable for applications such as multiphase catalysis and the removal of heavy metal ions and oil from water.
Materials with hierarchically organized pore systems—meaning that the walls of macropores with diameters in the micrometer range contain mesopores of just a few nanometers—are high on the wish lists of materials researchers. The advantages of these materials include their high surface area and the easy accessibility of the small pores through the larger ones. The great desirability of these materials is matched by the degree of difficulty in producing them on an industrial scale.
Scientists at Fudan University (China) and Monash University (Australia) have now successfully produced an ultralight iron oxide framework with 250 µm and 18 nm pores in a process that can be used on an industrial scale.
A team led by Gengfeng Zheng and Dongyuan Zhao used highly porous polyurethane sponges as a “matrix”, which were soaked with yellow potassium hexacyanoferrate (K4[Fe(CN)6]). Subsequent hydrolysis resulted in cubic nanocrystals of Prussian blue (iron hexacyanoferrate), a dark blue pigment, which were deposited all over the surfaces of the sponge.
The polyurethane sponge was then fully burned away through pyroloysis and the Prussian blue was converted to iron oxide. The result is a 3D framework of iron oxide cubes that are in turn made of iron oxide nanoparticles and contain mesopores. The material is so light that the researchers were able to balance a 240 cm3 piece on an oleander blossom.
Simple modifications allow the surface of the 3D framework to be varied from strongly hydrophilic to strongly hydrophobic for different applications. The researchers demonstrated this by removing arsenic ions from contaminated water and by separating water from gasoline. In the latter experiment, the resol-coated iron oxide framework absorbed more than 150 times of its own weight in gasoline.
The resol-coated frameworks are also suitable for use as nanoreactors for catalytic multiphase reactions between hydrophilic and hydrophobic reactants, which can normally only be made miscible through addition of various phase-transfer reagents and cosolvents. With the resol-coated iron oxide framework, the reaction runs much faster and more selectively without these additives, giving high yields. This is because of the tunable hydrophilic/hydrophobic surfaces of the mesopores, which take in both reagents and bring them into contact with each other. The catalyst can be retrieved magnetically, because the iron oxide nanoparticles of the 3D frameworks are superparamagnetic.
Author: Dongyuan Zhao, Fudan University, Shanghai (China), http://www.mesogroup.fudan.edu.cn/
Title: Ultralight Mesoporous Magnetic Frameworks by Interfacial Assembly of Prussian Blue Nanocubes
Angewandte Chemie International Edition, Permalink to the article: http://dx.doi.org/10.1002/anie.201308625
Dongyuan Zhao | Angewandte Chemie
Individual Receptors Caught at Work
19.10.2017 | Julius-Maximilians-Universität Würzburg
Rapid environmental change makes species more vulnerable to extinction
19.10.2017 | Universität Zürich
University of Maryland researchers contribute to historic detection of gravitational waves and light created by event
On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...
Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.
Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....
Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).
When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...
Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.
How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...
Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.
It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...
17.10.2017 | Event News
10.10.2017 | Event News
10.10.2017 | Event News
19.10.2017 | Materials Sciences
19.10.2017 | Materials Sciences
19.10.2017 | Physics and Astronomy