Stomata-like metal peptide coordination polymer

The water-triggered reversible transformation plays a significant role in bio-systems. To develop artificial materials with reversible structural transformability under mild conditions would be helpful to understand how bio-systems work. Here we report on a flexible coordination polymer, Cu–(Gly–Thr)·2H2O, whose structure can be controlled by humidity or temperature. This porous coordination polymer shows reversible single-crystal to single-crystal transformation with surprisingly high thermal stability. It was found that the ordered transformation occurs via coordination bonds breaking and reforming without changing the coordination numbers and valence of the copper ion. This reversible transformation makes it especially efficient at taking up CO2 under wet conditions, which is similar to the function of plant stomata.