Sensitive Current Sensor Based on a Lanthanide Framework with Lewis Basic Bipyridyl Sites for Cu 2+ Detection.

A new Yb-based three-dimensional metal-organic framework with free Lewis basic sites, [Yb 2 (ddbpdc) 3 (CH 3 OH) 2 ] (referred to as ACBP-6), from YbCl 3 and (6 R ,8 R )-6,8-dimethyl-7,8-dihydro-6 H -[1,5]dioxonino[7,6- b :8,9- b ']dipyridine-3,11-dicarboxylic acid (H 2 ddbpdc) was synthesized by a conventional solvothermal method. Two Yb 3+ are connected by three carboxyl groups to form the [Yb 2 (CO 2 ) 5 ] binuclear unit, which is further bridged by two carboxyl moieties to produce a tetranuclear secondary building unit. With further ligation of the ligand ddbpdc 2- , a 3-D MOF with helical channels is constructed. In the MOF, Yb 3+ only coordinates with O atoms, leaving the bipyridyl N atoms of ddbpdc 2- unoccupied. The unsaturated Lewis basic sites make this framework possible to coordinate with other metal ions. After growing the ACBP-6 in situ into a glass micropipette, a novel current sensor is formed. This sensor shows high selectivity and a high signal-to-noise ratio toward Cu 2+ detection with a detection limit of 1 μ M, due to the stronger coordination ability between the Cu 2+ and the bipyridyl N atoms.