Co3O4@Zn-BTC MOF as a novel nano-photocatalyst for degradation of toluene from ambient air

The present work aimed to synthesise and utilise a novel Co3O4@Zn-BTC Metal-Organic Framework (MOF) photocatalyst to decompose toluene in a dynamic stream under visible light. Nano-catalyst was prepared by a simple and facile solvothermal procedure and was characterised via various techniques included of PXRD, FE-SEM, TEM, BET, UV-VIS with DRS, and FT-IR. To optimise the effects of process parameters, namely relative humidity, toluene input concentration and flow rate on toluene degradation efficiency, the process was modelled using response surface methodology based on central composite design (RSM-CCD). RSM-CCD approach developed a quadratic polynomial model with R2 = 0.9989, adjusted R2 = 0.9980 and p-value <0.001. The optimal values of the input variables based on the obtained model were found to be 20 ppm vapour concentration, 30% RH and 15 ml/min. Under this condition, 40% Co3O4@Zn-BTC MOF showed the highest photocatalytic efficiency (64.1%) in toluene mineralisation compared to other photocatalysts (40% > 60% > 20% > 10% Co3O4@Zn-BTC > Zn-BTC). Among the studied variables, humidity (%) had the greatest efficacy on the decomposition efficiency of toluene. These outcomes could be attributed to the assembly of Co3O4 nanoparticles with Zn-BTC to form a heterogeneous structure of Co3O4@Zn-BTC MOF that expands the light absorption in the visible scope. The findings also demonstrated that the 40% Co3O4@Zn-BTC MOF photocatalyst possesses excellent stability in long-term exposure to toluene removal. Also, any by-products at the output of the photocatalytic system were not detected by GC-MS. The study shows promising ability of the MOF in photocatalytic oxidation of toluene and provides valuable information for further practical applications of the system in air purification.