Ultra sensitive ammonia sensing using TDA Schiff base MOFs: complementary strategy for gas detection at room temperature

The prompt and effective identification of ammonia (NH 3 ), classified as a hazardous volatile organic compound (VOC), is essential for the purposes of environmental monitoring and ensuring industrial safety. In the present investigation, a Schiff base ligand, TDA [terephthalylidene diisophthalic acid], was used to synthesize Zn( TDA ) and Co( TDA ) metal-organic frameworks (MOFs), through a solvothermal approach. Zn( TDA )MOF demonstrated a notable gas-sensing response (S = 137.1) to NH 3 at a concentration of 50 ppm, exhibiting an impressive detection range extending from 1 ppm to 50 ppm under ambient temperature conditions. The enhanced sensing performance of Zn MOF is attributed to the highly porous structure, with an average pore size of 29.9 nm and a significant surface area of 138.2 m 2 /g, which enhances gas adsorption and diffusion. The sensing mechanism follows a chemisorption-driven charge transfer process, in which NH 3 molecules engage with the Zn 2+ metal centers and Schiff base (-C N-) moieties. The robust electronic interaction markedly enhances sensitivity, concurrently reducing cross-sensitivity to other VOCs. Furthermore, the high porosity facilitates rapid diffusion of NH 3 molecules, leading to quick adsorption/desorption, which accelerates response and recovery kinetics and gas sensing stability studies of Zn(TDA)MOF as a promising candidate for detecting low-concentration NH 3 and enabling real-time applications. Zn( TDA )MOF showed a good response at 1 ppm to 50 ppm (Response S = 137.1 at 50 ppm) towards ammonia gas due to its high porosity (29.99 nm) and large surface area (138.134 m 2 /g). This study highlights the capabilities of Schiff base-derived MOFs as innovative gas sensors characterized by enhanced sensitivity and stability, thereby facilitating the development of advanced technologies for environmental monitoring. • A novel Schiff-based Zn/Co(TDA) MOF was synthesized via solvothermal method for room temperature NH 3 sensing. • Zn( TDA ) MOF exhibited ultra-senstive NH 3 detection (137 s) from 1 to 50 ppm at ambient temperature. • A strong interaction between the electron-rich aromatic framework and the analyte molecules is responsible for the remarkable sensitivity and selectivity of the MOF toward ammonia, acetic acid and formaldehyde. • Zn( TDA ) MOF exhibited remarkable sensitivity due to its high porosity(29.9 nm) and large surface area (138.1 m 2 /g). • The sensor showed excellent selectivity, reproducibility, and long-term stability over 30 days.