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

•A porous coordination polymer has reversible crystalline-to-amorphous transition (CAT).•The CAT is subtly controlled by the evacuation and implantation of the guest waters.•A significant fluorescence shift by 31 nm is firstly observed in coordination polymers.•The coordination polymer implys its great potentials as sensing materials.

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 31 nm, implying its great potential in fluorescence sensing of the environment humidity.

Graphical abstractAn extremely rare reversible crystal-to-amorphous transition accompanying with significant fluorescence shift is subtly controlled by the evacuation and implantation of the guest waters in a porous 2D CP, implying its great potential in humidity sensing.Figure optionsDownload full-size imageDownload as PowerPoint slide