Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


MOF co-catalyst allows selectivity of branched aldehydes of up to 90%


Approach represents a powerful tool for designing selective catalytic heterogeneous processes

Efforts to develop heterogeneous catalysts that appeal to the fine chemical industry have been limited by underwhelming results. Although some approaches have shown promising catalytic activity, "heterogenization" itself is not enough.

Micropores of MOFs with certain topologies increase the density of the olefins while partially preventing the adsorption of the synthesis gas.

Credit: @PSI

To be adopted by industry, heterogeneous catalysts must promote selectivity that is difficult or even impossible to obtain with existing catalytic systems--the chemical properties of any proposed heterogeneous catalysts must go beyond easier separation and recycling.

The chemical-flexibility, tuneable pore size and chemical and structural stability of metal-organic frameworks (MOFs) makes them ideal for designing active sites at the molecular level. Able to selectively adsorb different molecules depending on their structure, they can direct selectivity and reaction performance.

Many promising catalytic applications using MOFs as precursors for novel materials as well as model systems for understanding heterogeneous catalysis processes have been described. The field of catalysis by MOFs is still in its infancy though since most examples are proof-of-concepts and do not offer attractive advantages to existing catalysts.

In the paper Metal-organic frameworks as kinetic modulators for branched selectivity in hydroformylation, researchers from the Paul Scherrer Institute's Syncat Group, led by Marco Ranocchiari, and EPFL's Laboratory of Molecular Simulation, a computational group led by Berend Smit, used the example of hydroformylation to show how adsorption properties of MOFs can be exploited in catalysis to get results that have otherwise been inaccessible.

The methods presented can be used to predict the effect of such microporous co-catalysts in increasing selectivity in any homogeneous or heterogeneous catalytic reaction.

Hydroformylation, or oxo synthesis, is an industrial process for obtaining aldehydes from olefins. Current catalytic processes yield both linear aldehydes, which are key intermediates for the detergent and polymer industry, and branched ones, which are considered a powerful tool for the fine chemical industry because of their possible use in producing enantioenriched products, that is, products featuring a greater proportion of a given enantiomer of a chiral substance.

The linear isomers are often formed with rhodium catalysts. Branched aldehydes are formed from rhodium catalysts with bidentate ligands with directing groups to enhance selectivity. Producing the sought-after branched isomers without these directing groups is still a challenge though and can only be achieved through complex Rh catalysts.

They have been shown to result, for instance, in a selectivity for 2-methylhexanale from 1-hexene up to 75% and up to 86% for 2-methylbutanale from 1-butene.

The researchers first screened several catalytic conditions to maximize the yield of the branched product that could be obtained with homogeneous catalysis. They then showed how they could go beyond this limit and achieve much higher branched selectivity by adding MOFs to the reaction mixture. They also tested different MOF topologies to understand the role of the MOF environment in such a change in selectivity.

The group was able to show that the micropores of MOFs push the cobalt-catalyzed hydroformylation of olefins to kinetic regimes that favor high branched selectivity, without the use of any directing groups. The addition of MOFs allowed branched selectivity of up to 90% in these cases, a feat that cannot be achieved with existing catalysts.

Monte Carlo and density functional theory simulations combined with kinetic models show that the micropores of MOFs with certain topologies increase the density of the olefins while partially preventing the adsorption of the synthesis gas--this is what leads to the high branched selectivity.

Though the research focused on aldehydes, the methods presented can be used to predict the effect of microporous co-catalysts in increasing selectivity in any homogeneous or heterogeneous catalytic reaction.

Researchers can determine the microporous material that has the best chances of increasing selectivity by first choosing those that can adsorb the catalyst while being inert under reaction conditions, and by then using simulations to determine how the microporous materials might change the local concentration of the selectivity determining reactant(s) within the micropores.

Carey Sargent | EurekAlert!
Further information:

More articles from Life Sciences:

nachricht TU Dresden chemists develop noble metal aerogels for electrochemical hydrogen production and other applications
06.04.2020 | Technische Universität Dresden

nachricht First SARS-CoV-2 genomes in Austria openly available
03.04.2020 | CeMM Forschungszentrum für Molekulare Medizin der Österreichischen Akademie der Wissenschaften

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: When ions rattle their cage

Electrolytes play a key role in many areas: They are crucial for the storage of energy in our body as well as in batteries. In order to release energy, ions - charged atoms - must move in a liquid such as water. Until now the precise mechanism by which they move through the atoms and molecules of the electrolyte has, however, remained largely unknown. Scientists at the Max Planck Institute for Polymer Research have now shown that the electrical resistance of an electrolyte, which is determined by the motion of ions, can be traced back to microscopic vibrations of these dissolved ions.

In chemistry, common table salt is also known as sodium chloride. If this salt is dissolved in water, sodium and chloride atoms dissolve as positively or...

Im Focus: Harnessing the rain for hydrovoltaics

Drops of water falling on or sliding over surfaces may leave behind traces of electrical charge, causing the drops to charge themselves. Scientists at the Max Planck Institute for Polymer Research (MPI-P) in Mainz have now begun a detailed investigation into this phenomenon that accompanies us in every-day life. They developed a method to quantify the charge generation and additionally created a theoretical model to aid understanding. According to the scientists, the observed effect could be a source of generated power and an important building block for understanding frictional electricity.

Water drops sliding over non-conducting surfaces can be found everywhere in our lives: From the dripping of a coffee machine, to a rinse in the shower, to an...

Im Focus: A sensational discovery: Traces of rainforests in West Antarctica

90 million-year-old forest soil provides unexpected evidence for exceptionally warm climate near the South Pole in the Cretaceous

An international team of researchers led by geoscientists from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) have now...

Im Focus: Blocking the Iron Transport Could Stop Tuberculosis

The bacteria that cause tuberculosis need iron to survive. Researchers at the University of Zurich have now solved the first detailed structure of the transport protein responsible for the iron supply. When the iron transport into the bacteria is inhibited, the pathogen can no longer grow. This opens novel ways to develop targeted tuberculosis drugs.

One of the most devastating pathogens that lives inside human cells is Mycobacterium tuberculosis, the bacillus that causes tuberculosis. According to the...

Im Focus: Physicist from Hannover Develops New Photon Source for Tap-proof Communication

An international team with the participation of Prof. Dr. Michael Kues from the Cluster of Excellence PhoenixD at Leibniz University Hannover has developed a new method for generating quantum-entangled photons in a spectral range of light that was previously inaccessible. The discovery can make the encryption of satellite-based communications much more secure in the future.

A 15-member research team from the UK, Germany and Japan has developed a new method for generating and detecting quantum-entangled photons at a wavelength of...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

International Coral Reef Symposium in Bremen Postponed by a Year

06.04.2020 | Event News

13th AKL – International Laser Technology Congress: May 4–6, 2022 in Aachen – Laser Technology Live already this year!

02.04.2020 | Event News

“4th Hybrid Materials and Structures 2020” takes place over the internet

26.03.2020 | Event News

Latest News

TU Dresden chemists develop noble metal aerogels for electrochemical hydrogen production and other applications

06.04.2020 | Life Sciences

Lade-PV Project Begins: Vehicle-integrated PV for Electrical Commercial Vehicles

06.04.2020 | Power and Electrical Engineering

Lack of Knowledge and Uncertainty about Algorithms in Online Services

06.04.2020 | Social Sciences

Science & Research
Overview of more VideoLinks >>>