Reversible switching of Cu-tetracarboxylic-based coordination polymers through in situ single-crystal-to-single-crystal structural transformation and their impact on carbon-based composite derivatives, fluorescence, and adsorption properties

Two Cu-based coordination polymers (CPs), namely, complex 1 and complex 2 , with different frameworks were chosen to study reversible switching behavior through in situ single-crystal-to-single-crystal (SCSC) structural transformation. Notably, when complex 2 was soaked under strongly alkaline conditions (pH ​= ​13 for 10 ​min and very briefly at pH ​= ​14), it was completely converted into complex 1 . After complex 1 had been exposed to hot air to yield product 2 about 1 ​min. These in situ structural transformations were thoroughly investigated via the single crystal X-ray diffraction. Remarkably, the synthesized complexes were also used as a selective fluorescent probe for the fluorescence sensing of La 3+ ions. Our findings demonstrate that both complexes and their “Graphene-Carbon Nanotube” (G-CNT) hybrid derivatives display selective adsorption capacities toward Congo Red (CR) in aqueous solutions and that these complexes can be reuse. The SCSC conversion between two ultrastable Cu-based CPs is reversible. Due to the excellent water stability, the Cu-based CPs are potential selective fluorescent sensors for La 3+ ions in aqueous solution. Moreover, the title CPs and G-CNTs can be ideal sorbents for the selective removal of CR from water. • Two Cu-CP show the first SCSC transformation which has been achieved by varying the pH. • The use of CPs as fluorescent sensors for lanthanide ions is still rare. • There is no report of non-fluorescent CP sensors for La 3+ ions. • The carbon derivatives are synthesized from the precursors of CPs by the CVD method. • Both CPs and their carbon derivatives display selective adsorption capacities toward CR.