This illustration shows simultaneous photocatalytic hydrogen generation and dye degradation using a visible light-active metal-organic framework. Image: Alina-Stavroula Kampouri/EPFL.Some of the most useful and versatile materials today are metal-organic frameworks (MOFs). This class of material demonstrates structural versatility, high porosity, and fascinating optical and electronic properties, all of which makes MOFs promising candidates for a variety of applications, including gas capture and separation.
Because MOFs are so versatile in both their structural design and usefulness, material scientists are currently testing them for a number of chemical applications. One of these is photocatalysis, which involves exciting a light-sensitive material with light to dislocate electrons from their atomic orbits and leave behind ‘electron holes’. The generation of such electron-hole pairs is a crucial step in any light-dependent energy process, and, in this case, allows MOFs to catalyze a variety of chemical reactions.
A team of scientists at EPFL Sion in Switzerland, led by Kyriakos Stylianou at the Laboratory of Molecular Simulation, has now developed a MOF-based system that can perform not one but two types of photocatalysis simultaneously: producing hydrogen and cleaning pollutants from water. The material, which is described in a paper in Advanced Functional Materials, contains cheap and abundantly available nickel phosphide (Ni2P), and was found to carry out efficient photocatalysis under visible light, which accounts for 44% of the solar spectrum.
The first type of photocatalysis, hydrogen production, involves a reaction called ‘water-splitting’. As the name suggests, this reaction splits water molecules into hydrogen and oxygen. One of the main applications for water-splitting is in producing the hydrogen for fuel cells, which are already used in satellites and space shuttles but could one day also power motor vehicles.
The second type of photocatalysis is ‘organic pollutant degradation’, which refers to processes that break down the pollutants present in water. Stylianou and his team investigated the ability of this innovative MOF-based photocatalytic system to degrade the toxic dye rhodamine B, which is commonly used to simulate organic pollutants.
They performed tests of both types of photocatalysis in sequence, showing that the MOF-based system was able to integrate the photocatalytic generation of hydrogen with the degradation of rhodamine B in a single process. This means it is now possible to use this photocatalytic system to clean pollutants out of water while simultaneously producing hydrogen that can be used as a fuel.
"This noble-metal free photocatalytic system brings the field of photocatalysis a step closer to practical 'solar-driven' applications and showcases the great potential of MOFs in this field," says Stylianou.
This story is adapted from material from EPFL, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.