Environmental catastrophes have not been relegated to the developing world. Industrial contamination has affected millions of people, highlighting the need for simple and cost-effective methods to detect and remove harmful pollutants from water and soil. To investigate solutions, we have designed and synthesized novel luminescent metal-organic frameworks (LMOFs) by incorporating a strongly emissive molecular fluorophore with functionally diverse colinkers into Zn-based materials. LMOF-263, a member of a series of isoreticular compounds generated to analyze interactions with heavy metal ions in water, exhibits a sensitive response to Hg2+ and Pb2+ (3.3 ppb Hg2+, 19.7 ppb Pb2+). LMOF-263 is selective for Hg2+ over light metals, exhibiting detection ratios of 167.4 and 209.5 for Hg2+/Ca2+ and Hg2+/Mg2+, respectively. The quenching efficiencies determined for Hg2+ and Pb2+ (KSV values for Hg2+—459,446 M-1 and Pb2+—55, 017 M-1) were the second-highest and highest recorded values, respectively, among LMOFs at the time of publication. LMOF-263 also selectively extracts Hg2+ from water (maximum adsorption capacity—380 mg Hg2+/g), removing 99.1% of the metal within 30 min. High performances in both detection and extraction are invaluable in environmental remediation. Selectivity is a vital trait of LMOF sensors, especially if toxicity changes depending on slight structural differences. LMOF-271 is another dual-ligand material that selectively interacts with the organic contaminant carbon tetrachloride over similarly structured compounds chloroform and dichloromethane. The high quenching efficiency of LMOF-271 (KSV = 48,903 M-1, detection limit = 22 ppb) represents a benchmark as the first LMOF to effectively detect carbon tetrachloride via luminescence intensity changes. Dual-ligand LMOFs provide a unique scaffolding to monitor ultra-low concentrations of various environmental contaminants and aid remediation efforts.

Dual-ligand luminescent metal-organic frameworks towards environmental remediation efforts

255th National Meeting (2018)

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