Peculiar phenomena of structural transformations triggered from a nickel coordination polymer

Structural transformation has aroused wide interest and has emerged as a promising approach for the design and synthesis of novel coordination polymers. In this work, we found interesting structural transformation phenomena triggered from a nickel coordination polymer (CP). Two temperature-dependent two-dimensional (2D) CPs, 1 and 2 were synthesized from hydrothermal reactions, while the other two CPs, 2D 3 and 3D 4 were the products of the in situ thermal decomposition of 1. Interestingly, 1 could undergo methanol-mediated transformation to afford 2 and 2 might convert to 1 under the condition of adding bipy in water. The multi-step conversions from 1 to 3 and 3 to 4 triggered by heat treatment in the solid state accompany the very rare dynamic response of a sequential release of coordinated water and partial organic ligands. More importantly, the mechanism of the transformation has also been studied in detail. Moreover, 3 could revert back to 1 quickly upon exposure to air, and this reversible process of dehydration-rehydration could be repeated at least ten times, which could highlight the application for their use in moisture sensors.