Defect-Engineered Metal–Organic Frameworks with Coordinative Dye Modification for Cost-Effective Fluoride Detection in Water

Fluoride contamination in drinking water is a major global concern, affecting millions of individuals with varying degrees of fluorosis. The Great Rift Valley, encompassing Tanzania, Kenya, Malawi, Ethiopia, Sudan, Uganda, and Rwanda, is among the most severely impacted regions. In this work, we report a synthesis method to produce a low-cost material for fluoride detection based on defect engineering and coordinative postsynthetic modification of metal-organic frameworks (MOFs) using Rhodamine B. The method was optimized under varying conditions to enhance the material's response to fluoride ions and to elucidate the design parameters that augment sensing capabilities. The MOFs that exhibited the best response to fluoride were thoroughly characterized, and the kinetics of dye release in the presence of fluoride ions were investigated, including analyses in commercial mineral water and groundwater samples from Tanzania. The proposed methodologies were validated against standard quantification methods employing ion-selective electrodes below the maximum levels recommended by the World Health Organization (WHO) and the U.S. Environmental Protection Agency (US EPA).