| Structure–Performance Relationships in Metal–Organic Frameworks for Selective Nitrate Adsorption |
| کد مقاله : 1065-ICOC |
| نویسندگان |
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فاضل قهرمانی فرد *1، زهرا صفایی مقدم2، راضیه صفایی مقدم3 1گروه آموزش شیمی، دانشگاه فرهنگیان، تهران، ایران 2گروه آموزش شیمی، دانشگاه فرهنگیان، تهران ایران 3دانشگاه زاهدان |
| چکیده مقاله |
| Nitrate contamination in aquatic systems represents a critical public health concern, primarily due to its microbial reduction to nitrite, which triggers methemoglobinemia and facilitates endogenous formation of carcinogenic N-nitroso compounds [1]. To address this challenge, we investigate the performance, adsorption mechanisms, and structure–function relationships of advanced metal–organic frameworks (MOFs) for selective nitrate removal from water. A series of MOFs—including MOF-5, HKUST-1(Cu3(BTC)2), TUW-1(Cu2(Hbtc)2(bpe)2) and TUW-2 (Cu2(Hbtc)2(4,4’-bipy)2(H2O)2) were systematically evaluated under controlled conditions to identify key determinants of adsorption efficiency. Our experimental and comparative analysis demonstrates that ligand functionalization critically governs nitrate affinity. TUW-1 and TUW-2, incorporating tricarboxylic acid ligands with exposed –COOH groups, achieved record adsorption capacities of 119.42 and 105.93 mg/g, respectively—over 12 times higher than HKUST-1 (9.6 mg/g). This stark contrast arises from the availability of free acidic sites in TUW-1/2, enabling strong hydrogen bonding and monolayer Langmuir-type chemisorption, whereas HKUST-1 exhibits only weak electrostatic surface interactions due to fully coordinated carboxylates. Kinetic studies confirm pseudo-second-order behavior for TUW-1/2 and Fe-MIL-88B, indicating chemisorption-dominated mechanisms. Notably, TUW-1 and TUW-2 reached equilibrium within 30 minutes and retained structural integrity after 365 days in aqueous media, while HKUST-1 degraded within 72 hours. Mechanistic insights reveal three synergistic pathways: (i) electrostatic attraction between protonated frameworks (pH < pHzpc) and NO₃⁻, (ii) surface complexation via hard–hard interactions (e.g., Fe³⁺ with NO₃⁻), and (iii) hydrogen bonding with –COOH/–OH functionalities. This work establishes design principles for next-generation nitrate adsorbents: (1) incorporation of free acidic ligands, (2) optimization of pore accessibility, and (3) selection of hard Lewis acidic metal nodes. Our findings provide a robust foundation for scalable, field-deployable MOF-based water treatment systems. |
| کلیدواژه ها |
| Metal-organic frameworks, nitrate ion, water purification |
| وضعیت: پذیرفته شده |