Synthesis and Characterization of Metal-Organic Frameworks for Fluoride Adsorption and Catalytic Applications in Water Purification

Project Abstract

This study reports the synthesis, structural characterization, and performance evaluation of a novel family of metal-organic frameworks (MOFs) designed for simultaneous fluoride removal from aqueous systems and catalytic degradation of representative organic pollutants, addressing a critical gap in integrated water purification technologies. A series of isoreticular MOFs, featuring zirconium-based clusters and carefully chosen fluorinated and non-fluorinated organic linkers, were prepared via solvothermal routes under controlled pH, temperature, and solvent composition. The resulting crystalline materials were characterized by powder and single-crystal X-ray diffraction, thermogravimetric analysis, Brunauer–Emmett–Teller surface area measurements, pore size distribution, and spectroscopic techniques including Fourier-transform infrared, Raman, and solid-state 13C and 19F NMR to confirm linker coordination and fluorine incorporation. Morphology and particle size were examined by scanning electron microscopy and transmission electron microscopy, while pore accessibility and stability in water were assessed through dynamic light scattering and zeta potential measurements. Adsorption experiments demonstrated that the MOFs exhibit high fluoride uptake capacities across a wide pH window (4–9) with rapid adsorption kinetics, achieving equilibrium within minutes to a few hours depending on initial fluoride concentration and ionic strength. Isotherm analyses revealed a combination of Langmuir and Freundlich behavior, indicating heterogeneous adsorption sites and possible chemisorption contributions at higher fluoride loadings. Thermodynamic parameters indicated an endothermic, spontaneous process with increased randomness at the solid–solution interface. The presence of competing anions (chloride, sulfate, bicarbonate) was systematically evaluated to determine selectivity, revealing that framework topology and pore environment govern fluoride affinity. In situ FT-IR and X-ray absorption spectroscopy suggested the formation of inner-sphere complexes between fluoride ions and metal nodes, supported by increased framework rigidity upon adsorption as evidenced by solid-state NMR. In parallel, the MOFs were evaluated as heterogeneous catalysts for the degradation of model organics such as methylene blue and Rhodamine B, under visible-light irradiation and in a controlled oxidant environment. Photocatalytic performance correlated with accessible photogenerated charge carriers and the presence of coordinatively unsaturated metal sites, enabling efficient electron-hole separation and reactive oxygen species generation. Catalyst stability and reusability were confirmed across multiple cycles with negligible loss of activity, and post-reaction analyses indicated minimal framework degradation and sustained structural integrity. Combined fluoride adsorption and catalytic degradation tests were conducted in sequential and simultaneous operation modes to assess integration feasibility. The results show that the MOFs maintain high fluoride removal efficiency while enabling concurrent breakdown of organic contaminants, highlighting the potential for simplified water treatment train designs. Computational modeling using density functional theory and Grand Canonical Monte Carlo simulations complemented experimental findings by elucidating adsorption energetics, pore filling, and catalytic active-site distribution. This multidisciplinary study advances the development of multifunctional MOFs tailored for simultaneous contaminant removal and pollutant mineralization, offering a scalable route toward improved water purification with reduced treatment stages.

Project Overview

What This Project Is About

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A plain-language overview of the topic and what the project investigates.

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The Problem It Addresses

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What problem or gap this project tackles and why it matters to the field or society.

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Objectives of the Project

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1. Learn how to synthesize a metal-organic framework (MOF) in simple lab steps. 2. Characterize the fabricated MOFs to confirm structure and stability. 3. Test fluoride adsorption performance from water samples. 4. Explore basic catalytic reactions using the MOFs. 5. Compare results with a known reference material.

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What You Will Do Step by Step

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1. Review basic literature on MOFs, fluoride contamination, and catalysis. 2. Prepare MOF samples using a straightforward synthesis method. 3. Characterize the materials with simple techniques (e.g., basic spectroscopy, surface area estimation). 4. Gather fluoride adsorption data from water tests at different pH and concentrations. 5. Conduct small-scale catalytic tests to see if MOFs aid a chosen reaction. 6. Analyze data to identify trends and performance differences. 7. Discuss limitations and practical considerations for real-world use. 8. Present findings in a concise written report and a short presentation.

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Expected Outcome

A clear demonstration of MOF synthesis feasibility, measurable fluoride removal efficiency, and preliminary catalytic activity, with practical notes on how to scale or improve the system.