Fast fabrication, gas sense characteristics and kinetics of cubic Ti-BIPA-TC-MOF film composite optical waveguides

Abstract A cubic Ti-MOF ([Ti2-(TpA)2-H2BIPA]), constructed from a titanium metal center and a benzo-imidephenanthroline tetracarboxylic acid (H4BIPA-TC) ligand was photo-inductively grown on the surface of a titanium dioxide (TiO2) composite optical waveguide (COWG) substrate and the influence of photo-inductive growth period on the [Ti2-(TpA)2-H2BIPA] film surface morphology, optical properties and gas adsorption/sensing characteristics was investigated. The results showed that [Ti2-(TpA)2-H2BIPA] formed a cubic structure after grew for only 5 minutes. As an ideal gas adsorbent, it exhibits a specific response to ethylenediamine (EDA) among various benzene, amine and acid gases, due to the intrinsic electron deficiency, rich COOH active sites of the Ti-BIPA-TC-MOF-5 frame and the higher molar refractive indexes (RDs) or dipoles of EDA than other gases. In the EDA concentration range from 10 ppt to 100 ppm, the Ti-BIPA-TC-MOF-5 film COWG exhibited a rapid, repeatable response. Moreover, the Ti-BIPA-TC-MOF-5 film COWG was relatively stable, within 17 days of EDA detection, the response intensity was almost constant and slightly decreased within 40 days. In a static gas adsorption stage at 283-313 K, the EDA gas adsorption behaviour of the Ti-BIPA-TC-MOF-5 film is consistent with the pseudo-second-order (PSO) kinetic model.