Pre-Concentrating and Detecting Natural-Water Heavy Metals by Sulfur-Equipped Porous Crystals

To advance the technologies for environmental pollution monitoring, we here propose crystalline metal-organic frameworks (MOFs) combining robust porous, high-surface-area structures and extensive sulfur functions that proffer highly strong and selectivebinding affinities for convenient enrichment and sensing of heavy metal species in natural waters. For this, we will synthesize molecular building blocks equipped with two distinct sets of organic functions: one is the chemically hard and hydrophilic carboxylsthat favor chemically hard metal ions (e.g., Zr4+); the other is the chemically soft sulfur (thioether and thiol) function that does prefer heavy metal species. Thus, the hard carboxyl groups can be first engaged with a hard metal ion to form single crystals ofporous network based on the reversible metal-carboxylate coordination bonds, while the soft sulfur groups remain free-standing inside the pores. Because of the large surface area of the porous crystal, heavy metal species from water will be able to quickly diffuseinto the pores and access the chemical groups to trigger the color/emission changes for detection purposes. Moreover, the heavy metal species thus trapped and concentrated can be conveniently eluted by the very cheap I2/NaI solution for further quantificationand for recycling the original sorbent material.