Review on next-generation MOF-engineered smart nano sensors for ultra-trace environmental pollutant detection.

Environmental contamination caused by heavy metals, radioactive ions, antibiotics, pesticides, dyes, and other emerging pollutants has become a significant global concern due to their high toxicity, environmental persistence, and bioaccumulative nature. Although conventional analytical techniques provide high accuracy and sensitivity, their widespread practical application is often hindered by expensive instrumentation, complex operational procedures, and limited suitability for real-time monitoring. Metal-organic frameworks (MOFs), owing to their exceptionally high specific surface area, tunable pore architecture, structural diversity, and versatile host-guest interactions, have emerged as highly promising functional materials for environmental sensing and pollutant remediation. This review critically summarizes recent advances in MOF synthesis strategies, structural engineering, and hybrid nanocomposite development for luminescent, electrochemical, and colorimetric sensing, as well as their applications in pollutant detection and environmental remediation. Particular emphasis is placed on elucidating the relationships among synthesis strategies, particle size, defect density, porosity, and the resulting sensing performance. The fundamental sensing mechanisms, including photoinduced electron transfer (PET), Förster resonance energy transfer (FRET), the inner filter effect (IFE), the analyte coordination effect (ACE), charge transfer, and host-guest interactions, are comprehensively discussed. Furthermore, recent developments in MOF-based hybrid systems integrated with MXenes, graphene, conductive polymers, and nanozymes are highlighted for their enhanced electrical conductivity, sensing sensitivity, selectivity, and long-term operational stability. The review also addresses critical challenges, including matrix interference in complex environmental samples, hydrolytic instability, and metal ion leaching, together with effective mitigation strategies such as the incorporation of high-valence metal nodes, defect engineering, and hybrid composite formation to enhance structural durability and practical applicability. In addition, emerging smart sensing platforms incorporating microfluidic technologies, wearable electronics, wireless communication, smartphone-assisted analytical systems, and Internet of Things (IoT) connectivity are highlighted as promising approaches for next-generation environmental monitoring. Overall, this review provides comprehensive insights into the design principles, current challenges, and future prospects of MOF-based technologies for sustainable environmental sensing, efficient pollutant remediation, and intelligent wastewater treatment systems, thereby facilitating the development of next-generation environmental monitoring technologies.