Defects offer way to give MOFs enhanced abilities

The word ‘defect’ usually suggests some negative, undesirable feature, but researchers at the Energy Safety Research Institute (ESRI) at Swansea University in the UK have a different opinion. They’ve found that, in the realm of nanoporous materials, defects can be put to a good use, if one knows how to tame them.

A team led by Marco Taddei at Swansea University is investigating how the properties of metal-organic frameworks, a class of materials resembling microscopic sponges, can be adjusted by taking advantage of their defects to make them better at capturing carbon dioxide (CO₂).

"Metal-organic frameworks, or MOFs, are extremely interesting materials because they are full of empty space that can be used to trap and contain gases," explained Taddei. "In addition, their structure can be manipulated at the atomic level to make them selective to certain gases, in our case CO₂.

"MOFs containing the element zirconium are special, in the sense that they can withstand the loss of many linkages without collapsing. We see these defects as an attractive opportunity to play with the properties of the material."

The researchers investigated how defects take part in a process known as ‘post-synthetic exchange’, a two-step procedure whereby a MOF is initially synthesized and then modified through the exchange of some of the components of its structure. They studied the phenomenon in real time using nuclear magnetic resonance, which allowed them to understand the role of defects during the process. They report their findings in a paper in Angewandte Chemie.

"We found that defects are very reactive sites within the structure of the MOF, and that their modification affects the property of the material in a unique way." said Taddei. "The fact that we did this by making extensive use of a technique that is easily accessible to any chemist around the globe is in my opinion one of the highlights of this work."

"In ESRI, our research efforts are focused on making an impact on the way we produce energy, making it clean, safe and affordable," said co-author Andrew Barron, ESRI director. "However, we are well aware that progress in applied research is only possible through a deep understanding of fundamentals. This work goes exactly in that direction."

The study is a proof of concept, but these findings lay the foundation for future work. The researchers want to learn how to chemically manipulate defective structures to develop new materials with enhanced performance for CO₂ capture from steelworks waste gases, in collaboration with Tata Steel and University College Cork in Ireland.

"Reducing the CO₂ emissions derived from energy production and industrial processes is imperative to prevent serious consequences on climate," said co-author Enrico Andreoli, a senior lecturer at Swansea University and leader of the CO₂ capture and utilization group within ESRI. "Efforts in our group target the development of both new materials to efficiently capture CO₂ and convenient processes to convert this CO₂ into valuable products."

This story is adapted from material from Swansea University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.