ZnNi(NA) (NA= Nicotinic acid) bimetallic mesoporous MOFs as a sensing platform for ethanol, formaldehyde and ammonia at room temperature

A novel bimetallic ZnNi(NA) (NA = Nicotinic acid) MOF nanomaterials with molar ratios of 3:1; 1:1; and 1:3 are deployed as sensing materials for detection of NH3, HCHO and C2H5OH vapours at room temperature. These metal-organic frameworks (MOFs) were synthesized in 3:1 methanol and water solvents at 130 °C by solvothermal method. Several characterization techniques, like XRD, FT-IR, SEM, EDS, elemental analysis, TGA, and XPS, are used for structural illustration. Zn/Ni bimetallic MOFs exhibited smaller particle sizes and superior surface areas compared with Zn(NA) and Ni(NA) monometallic MOFs. ZnNi(NA)-1:1 showed a microporous nature, while ZnNi(NA)-3:1, ZnNi(NA)-1:3 and Zn(NA) are mesoporous nature. All the materials exhibited good thermal stability up to 450 °C temperature. The sensor-based on porous ZnNi(NA)-1:1 nanomaterial (≈2.4 nm) exhibits the best sensing performance towards ammonia at 50 ppm concentration. The ZnNi(NA)-1:1 material showed more response (Ra/Rg = 291) compared to the monometallic compounds Ni(NA) (Ra/Rg = 119) and Zn(NA) (Ra/Rg = 64). All sensors have good reproducibility and excellent long-term stability.