Guest water-controlled reversible crystalline-to-amorphous transition and concomitant fluorescence shift in a polar open coordination polymer

Abstract

This work presents a polar porous coordination polymer with new topological prototype, named {[Zn(ndca)(bpp)]·(H2O)5}n (H2ndca=5-norbornene-2,3-dicarboxylic acid and bpp=1,3-bis(4-pyridyl) propane). Each the borehole-shaped linear channel is encapsulated with one spiral water tape built by alternate array of the quadrangular and hexagon water clusters. The crystals display a reversible crystal-to-amorphous transformation through subtly manipulating over the evacuation and uptake of the guest water tapes confined in the channels upon performing the dehydrated-rehydrated process and I2-exchanged experiment. The results show that the polar crystalline structure is stabilized by the well-orientated H-bonds between the host framework and guest water tape, which are also responsible for the prefect host-guest chiral matching. The most distinguished feature for this material is attribuated to the reversible crystalline-to-amorphous phase transition that is accompanied with a significant fluorescence shift by 31nm, implying its great potential in fluorescence sensing of the environment humidity.