  The fundamental understanding of water confined in porous coordination
polymers (PCPs) is significantly important not only for their applications such
as gas storage and separation, but also for exploring the confinement effects
in the nanoscale spaces. Here, we report the observation of an exotic water in
the well-designed hydrophilic nanopores of PCPs. Single-crystal X-ray
diffraction found that nanoconfined water has an ordered structure that is
characteristic in ices, but infrared spectroscopy revealed a significant number
of broken hydrogen bonds that is characteristic in liquids. We found that their
structural properties are quite similar to those of solid-liquid supercritical
water predicted in hydrophobic nanospace at extremely high pressure. Our
results will open up not only new potential applications of exotic water in
PCPs to control chemical reactions but also experimental systems to clarify the
existence of solid-liquid critical points.
