Self‐Healing 2D Anion‐Organic Frameworks for Low‐Temperature Water Release

Abstract Molecular frameworks have recently shown a great potential in atmospheric water harvesting, in which the water release at low temperatures is challenging. Anion‐organic frameworks based on anion‐coordination chemistry are presented herein to meet this challenge. These frameworks are prepared as tubular single crystals in pure water from the in situ protonation and crystallization of pyridine‐terminated triphenylamine derivatives with hydrochloric or hydrobromic acid. They possess a 2D honeycombed porous structure and carry halogen anions confined within 1D hexagonal nanochannels with a modular size of 1.7–2.3 nm. They exhibit a high water uptake of up to 0.87 g g −1 and a water release onset temperature as low as −90 °C. The water uptake and release induce significant changes in the crystal morphology and absorption and emission properties of these framework crystals, providing a visual indication of their hydration states over a wide temperature range. The kinetics of dehydration at subglacial temperatures is successfully determined by emission spectral shifts. These framework crystals show a high water‐stability and can be used for repeated water capture and release thanks to a rapid and robust self‐healing capability. This discovery opens opportunities for the design and synthesis of flexible and self‐healing frameworks for porosity‐related applications.