Scientists have developed a light-responsive crystalline material, which has the ability to change its porous nature. This porous framework with the structural flexibility of that provides a highly efficient photochemical electrocyclization in a single-crystal-to-single-crystal manner.

The innovational development was made by the scientific group from the Kyoto University in collaboration with the University of Tokyo.

Photochromic molecules are substances, which display colour changes upon photoirradiation. They are characterized by changes of geometric structures, electronic states, and chemical and physical properties. These molecules are an important element in creating of different photoresponsive materials such as polymers, gels and liquid crystals. Photochromic molecules are highly-useful as they can be applied in medicine. For example, it can help to control drug release in the complicate medicine delivered mechanism or to generate dynamic scaffolds for tissue engineering. Furthermore, porous coordination polymers (PCPs) or metal-organic frameworks (MOFs) represent a highly-demand new class of porous materials with crystalline frameworks.

Consequently, scientists managed to develop a framework with the flexibility, which provides a sufficient room for structural changes of the dithienylethene (DTE) moieties for quantitative conversion during photoisomerization. The crystal also contains zinc ions (Zn2+) and 1,4-benenzenedicarboxylate.

The team created a PCP, which demonstrates a highly effective isomerization and cooperative structural transformations by combining flexible frameworks with DTE derivatives. The synthesis and characterization of a photoresponsive PCP with a twofold interpenetrated framework composed of a DTE-based ligand. Taking advantage of the flexible nature of the entangled framework, the porous crystal shows a quantitative and reversible isomerization upon UV and visible light irradiation, which is applicable to reversible photomodulation of its gas sorption properties. The material is able to absorb CO2, nitrogen at various temperatures, under the influence of visible and ultraviolet light.

Due to the flexibility of the structure, channels have changed under the influence of light. The distance between the 2 layers decreased with ultraviolet irradiation, then expanded with the light of visible light.