The researchers note that most porous materials are made from linkers and connecting units—metal-organic frameworks are one example. Such frameworks are often custom-developed to allow for storing other material, such as hydrogen, in the pores. The downside to such an approach is the multitude of options available, which requires researchers to spend time screening for the optimal structure. In this new effort, the researchers report on the development of a new porous material made from a single synthesized molecule. They claim it is possible to create a complex, useful type of material without a complex set of building blocks.
The molecule the team made had a symmetrical outer shell, giving it a shape akin to a propeller. It consisted of three polar dipyridylphenyl parts hooked to a middle non-polar mesitylene. In the presence of isopropanol or acetonitrile, it assembled automatically into a network that was held together by hydrogen bonds (non-classical). The researchers note that the bonds were weaker than normal hydrogen bonds but were stable up to 202°C. They further note that other similar-purpose crystals begin to degrade at temperatures of 130°C. Above the stable point, the pores in the crystal started to collapse causing the material to become non-porous—suggesting a means for delivering a material that it has been holding. Interestingly, the researchers found that the pores could be regenerated by cooling the material and treating it with acetonitrile vapor—a form of self-healing.
Image courtesy of phys.org