Synthesis, characterization and sensing applications of TiO2 doped MOF composites for selective detection of ammonia at room temperature

Abstract

Herein, we have developed a highly sensitive chemiresistive TiO2 doped metal–organic framework(MOF) composite-based sensor for ammonia detection at room temperature. Two novel Ti-MOFs@TiO2 composites are developed employing terephthalic acid and 2-amino terephthalic acid as organic linkers with Titanium tetra isopropoxide (TTIP) as a metal source by solvothermal technique. The morphology and crystallinity of synthesized compounds were characterized by using Field-emission scanning electron microscopy (FE-SEM) with EDX analysis, X-ray diffraction (PXRD), XPS and Brunauer–Emmett–Teller (BET) analysis techniques. MIL-125@TiO2 sensors exhibited a more specific surface area (374.74 m2 g−1) than the other three compounds. For gas-sensing applications, all composite materials were exposed to different gas vapours like ammonia, formaldehyde, acetic acid, ethyl alcohol, acetone, xylene, toluene and benzene at room temperature. The sensing results indicate that the sensors exhibit excellent response at low concentrations of ammonia, formaldehyde and acetic acid gases (1 ppm level). The enhanced sensor response was attributed to MIL-125@TiO2 (85 response at 50 ppm) and NH2-MIL-125@TiO2 (71 response at 50 ppm) towards ammonia gas and shows a better selectivity, sensitivity and repeatability to ammonia gas. All the materials exhibited less response times (between 8 and 45 sec) and more recovery times (between 13 and 125 sec).