A shape-shifting porous material that mimics the way proteins work looks promising as a catalyst, say researchers at the Department of Chemistry of the University of Liverpool, Liverpool, U.K. Proteins change their structures in response to their environment to carry out chemical processes. In contrast, the porous materials widely used in industry, both in catalysts for producing fuels and chemicals and in environmental remediation technologies such as adsorbers for removing harmful compounds from air and water, are rigid.
The Liverpool team has produced a flexible crystalline porous (pores <1 nm) material composed of metal ions and a small tri-peptide molecule that can change its structure in response to its environment to perform specific chemical processes.
Known as ZnGlyGlyHis (glycine, glycine and histidine – the tri-peptide), the material uses the same atomic-scale mechanisms as proteins to switch between structures.
“This offers exciting scientific possibilities, for example in catalysis, through the design of materials that can dynamically select the structure needed for a particular task,” says research lead professor Matt Rosseinsky.
Figure 1. Planned introduction of chemical functionality will allow carrying out specific catalytic and separation processes. Source: Department of Chemistry, the University of Liverpool.
“ZnGlyGlyHis is a proof-of-concept material that demonstrates key aspects of enzyme-like response in a synthetic porous material. The identification of specific applications forms part of our future development of this class of materials, as in the long term we envisage them enabling new types of catalytic and separation processes inspired by biology,” he adds.
Production involves simple solvothermal processing similar to that used in making synthetic zeolites — so, in principle, this class of material should be scalable. What will vary are the metal used and the synthesis cost and complexity of the organic molecule selected.
To understand the structural flexibility and activity of ZnGlyGlyHis, Rosseinsky’s researchers now are refining the experimental and computational techniques they developed. This should allow them to develop the next generation of functional flexible porous materials that can alter their structure in response to changes in the surrounding chemistry.
In particular, the researchers are targeting materials with larger pores to allow them to handle a wider range of molecules and chemical processes, introducing chemical functionality into the material that enables specific catalytic and separation processes, and expanding the range of molecular linkers that permit the enzyme-like response (Figure 1).
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Although the researchers haven’t developed the new material with an eye to particular industrial processes, they are in regular contact with a range of companies about the project’s progress and have industrial scientists involved in their discussions about the future direction of the work.