Isostructural Synthesis of Porous Metal–Organic Nanotubes

Employment of semirigid
double-hinged di-1,2,4-triazoles has led
to the synthesis of an isostructural series of metal–organic
nanotubes (MONTs). The ditriazole ligands adopt a syn conformation
between rigid metal chains while an appropriate anion choice provides
a “capping” of the metal ions, leading to MONT formation.
This approach of utilizing a variety of both semirigid ligands and
metals is the first general methodology to prepare this class of 1D
nanomaterial. The local geometry at the metal center depends on the
metal ion employed, with Cu­(I) centers adopting a tetrahedral geometry,
Ag­(I) centers adopting a seesaw geometry, and Cu­(II) centers adopting
a square-pyramidal geometry upon MONT synthesis. The pore size of
the MONTs is adjusted by changing the central portion of the double-hinged
ligand, allowing for a predictable method to control the pore width
of the MONT. The adsorption properties of MONTs as a function of pore
size revealed selective uptake of CO2 and CH4, with copper MONTs exhibiting the highest uptake. In the case of
the silver MONTs, an increase in pore width improves both gas uptake
and selectivity.