Emissive Substoichiometric Covalent Organic Frameworks for Water Sensing and Harvesting.

Emissive covalent organic frameworks (COFs) have recently emerged as next-generation porous materials with attractive properties such as tunable topology, porosity, and inherent photoluminescence. Among the different types of COFs, substoichiometric frameworks (so-called Type III COFs) are especially attractive due to the possibility of not only generating unusual topology and complex pore architectures but also facilitating the introduction of well-defined functional groups at precise locations for desired functions. Herein, the first example of a highly emissive (PLQY 6.8%) substoichiometric 2D-COF (COF-SMU-1) featuring free uncondensed aldehyde groups is reported. In particular, COF-SMU-1 features a dual-pore architecture with an overall bex net topology, tunable emission in various organic solvents, and distinct colorimetric changes in the presence of water. To gain further insights into its photoluminescence properties, the charge transfer, excimer emission, and excited state exciton dynamics of COF-SMU-1 are investigated using femtosecond transient absorption spectroscopy in different organic solvents. Additionally, highly enhanced atmospheric water-harvesting properties of COF-SMU-1 are revealed using FT-IR and water sorption studies.The findings will not only lead to in-depth understanding of structure-property relationships in emissive COFs but also open new opportunities for designing COFs for potential applications in solid-state lighting and water harvesting.

Uranyl uptake into metal-organic frameworks: a detailed X-ray structural analysis.

Metal-organic frameworks (MOF) are a subclass of porous framework materials that have been used for a wide variety of applications in sensing, catalysis, and remediation. Among these myriad applications is their remarkable ability to capture substances in a variety of environments ranging from benign to extreme. Among the most common and problematic substances found throughout the world's oceans and water supplies is [UO2]2+, a common mobile ion of uranium, which is found both naturally and as a result of anthropogenic activities, leading to problematic environmental contamination. While some MOFs possess high capability for the uptake of [UO2]2+, many more of the thousands of MOFs and their modifications that have been produced over the years have yet to be studied for their ability to uptake [UO2]2+. However, studying the thousands of MOFs and their modifications presents an incredibly difficult task. As such, a way to narrow down the numbers seems imperative. Herein, we evaluate the binding behaviors as well as identify the specific binding sites of [UO2]2+ incorporated into six different Zr MOFs to elucidate specific features that improve [UO2]2+ uptake. In doing so, we also present a method for the determination and verification of these binding sites by Anomalous wide-angle X-ray scattering, X-ray fluorescence, and X-ray absorption spectroscopy. This research not only presents a way for future research into the uptake of [UO2]2+ into MOFs to be conducted but also a means to evaluate MOFs more generally for the uptake of other compounds to be applied for environmental remediation and improvement of ecosystems globally.

Deep eutectic solvents comprising creatine and citric acid and their hydrated mixtures.

We report the phase diagram for the binary creatine-citric acid mixture which features a stable and broad eutectic region. Combinations containing 10-60 mol% creatine yield a deep eutectic solvent with a glass transition temperature at 270 K. Addition of up to 70 mol% water to the binary mixture affords retention of the eutectic nature and a handle to vary solvent viscosity and polarity.