Negative area compressibility of a hydrogen-bonded two-dimensional material.

Very few materials expand two-dimensionally under pressure, and this extremely rare phenomenon, namely negative area compressibility (NAC), is highly desirable for technological applications in pressure sensors and actuators. Hitherto, the few known NAC materials have dominantly been limited to 2D crystals bonded via coordination interactions while other 2D systems have not been explored yet. Here, we report the large NAC of a hydrogen-bonded 2D supramolecular coordination complex, Zn(CH3COO)2·2H2O, with a synergistic microscopic mechanism. Our findings reveal that such an unusual phenomenon, over a wide pressure range of 0.15-4.44 GPa without the occurrence of any phase transitions, arises from the complex cooperation of intra-layer coordination and hydrogen-bonding interactions, and inter-layer van der Waals forces. In addition, we propose that these NAC crystals could have important applications as pressure-converting materials in ultrasensitive pressure sensing devices.