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A trinuclear nickel cluster is the basis for a porous material with a highly connected and symmetric structure

Credit: © 2009 Wiley

Porous coordination polymers have simple and highly connected networks that form extremely open framework materials. Most of them are formed by four- or six-coordinate metal ions in a square planar, octahedral or trigonal prismatic environment.

Now, Xiao-Ming Chen, Jie-Peng Zhang and colleagues from Sun Yat-Sen University in Guangzhou have made a porous coordination polymer that has a three-metal-centred nine-connected building unit. The central cluster is a tricapped trigonal prism with dicarboxylate and pyridyl benzoate linkers. These units join together through the linkers to form tetrahedra whose faces are capped with trigonal pyramids, forming a 'triakis tetrahedron'.

The overall structure can be described as a body-centred, caesium-chloride-like, arrangement of these tetrahedra. The void around these that is accessible by solvent makes up over 21% of the crystal volume. The surface area of the material is over 2,000 m² g⁻¹, and the pore volume is 0.95 cm³ g⁻¹. The channel system contains three cavity types connected by three types of passages, and Chen and co-workers hope that these will lead to useful and interesting adsorption properties.