The interface effect of MOF-derived Pr6O11/SnO2 composite materials enhances oxygen vacancies for achieving highly sensitive detection of n-butanol gas

Abstract

Sn-MOF and Pr-MOF were synthesized respectively by using room temperature stirring and water bath heating. Pr₆O₁₁ and SnO₂ were obtained by separately calcining the synthesized MOF precursors. The x at% Pr₆O₁₁/SnO₂ composite material (x is the atomic ratio of Pr to Sn), a highly sensitive sensing material for detecting n-butanol, was fabricated by simply ultrasonically mixing Pr₆O₁₁ and SnO₂. The response value of the 6 at% Pr₆O₁₁/SnO₂ gas sensor to 100 ppm n-butanol at 220 °C is as high as 13 457. When the relative humidity reaches 80%, the response still maintains a high level of 6341, indicating impressive anti-humidity of the sensor. The sensor's cross-selection coefficient is greater than 4, so the sensor also has good selectivity. These sensing materials from the MOF retain their high specific surface area and highly ordered pore structure, which is conducive to the adsorption, diffusion and reaction of gases. The enhanced performance of the 6 at% Pr₆O₁₁/SnO₂ gas sensor is also due to the synergistic effect of the heterojunction, oxygen vacancies, and Pr³⁺/Pr⁴⁺ redox pairs. The heterojunction formed between Pr₆O₁₁ and SnO₂ improves the charge transfer efficiency, effectively suppresses the recombination of electrons and holes, and induces the generation of more oxygen vacancies. Oxygen vacancies can reduce the material band gap and the activation energy of the n-butanol reaction, and promote the reaction between oxygen molecules and electrons to generate more reactive oxygen species. The moisture resistance is attributed to the significant elimination of the influence of water molecules by the Pr³⁺/Pr⁴⁺ redox pairs.