A gas–liquid interface synthesis in polyoxometalate chemistry: potential bag filter for volatile organic amines

Diffusion of piperidine and pyridine into an acidified aqueous solution of ${\text{Na}}_2{\text{MoO}}_4$, yield compounds $\left[\right(\text{pipH}{)}_4\left]\right[{\text{Mo}}_8{\text{O}}_{26}]\cdot 4{\text{H}}_2\text{O}$$(\text{pip}=\text{piperidine}={\text{C}}_5{\text{H}}_{11}\text{N})$ (1) and $\left[\right(\text{pyH}{)}_4\left]\right[{\text{Mo}}_8{\text{O}}_{26}]$$(\text{py}=\text{pyridine}={\text{C}}_5{\text{H}}_5\text{N})$ (2), respectively. Compound 1 possesses supramolecular 3-D network and the relevant connectivity pattern generates channels of approximate dimensions of $10.76\times 11.57{\acute{\AA }}^2$, in which the piperidinium cations are located as guests. Multidimensional supramolecular frameworks (3-D in compound 1 and 2-D layer type of network in compound 2) have been made possible, as the organic cations and polyoxometalate (POM) anions are glued together by significant hydrogen bonding interactions. The synthesis of compounds 1 and 2 provides a unique 'gas–liquid' synthetic route in POM chemistry that result in organic–inorganic hybrid materials with structural diversities. This synthetic approach, first time in POM chemistry, can be described as a potential bag filter for volatile organic amines.

Graphical Abstract

Synopsis: Diffusion of piperidine and pyridine vapours into acidified aqueous molybdate solution leads to the formation of ion pair compounds having supramolecular framework structures. These organic amines are trapped as guest or as part of the framework making the present system a potential bag filter for the volatile organic amines. .