Advances in ZIF-8 variants: Synthesis, design, and applications in gas sensing

Zeolitic imidazolate framework-8 (ZIF-8), a subgroup of metal-organic frameworks, has garnered significant focus due to its remarkable structural tunability, chemical stability, and high surface area. These attributes make ZIF-8 and its derivatives desirable materials for drug delivery, catalysis, absorption of different gases, and gas sensing applications. This review comprehensively explains the current advances in the synthesis of ZIF-8 and its derivatives, emphasizing the various approaches, including solvothermal, mechanochemical, sonochemical, and seed-assisted methods, etc. The influence of critical parameters like linkers, solvents, pH, temperature, reaction flow rate, viscosity, interfacial tension, and reaction conditions on the morphology and performance of ZIF-8 is systematically analyzed. Furthermore, it explores the roles of ZIF-8-based materials in electrochemical sensing, highlighting their performance in sensing gases such as CO₂, NH₃, H₂S, volatile organic compounds, NO₂, and H₂. The mechanisms behind the sensing capabilities of pure, composite, and hybrid ZIF-8 are explained, emphasizing the structure-property relationship and the development of composites. Challenges such as reproducibility, scalability, and environmental stability are also addressed, alongside prospects for integrating ZIF-8 into next-generation gas sensors. This review provides insight into the synthesis-application nexus, aiming to guide future research towards the rational design of ZIF-8-based gas sensors with improved performance and practical utility.