Combined Adsorption And Photocatalytic Degradation Of Formaldehyde Over TiO₂@Titanium-Organic Framework Composite Photocatalysts

Formaldehyde?HCHO?,as the main pollutant in indoor air,has caused great harm to the human health.Therefore,the elimination of formaldehyde has become a key topic for indoor air pollution control.With the continuous research on photocatalytic technology in indoor air treatment,especially,the research on TiO₂ is the most extensive,and its disadvantages is also constantly emerging.The pure TiO₂ tends to aggregate,resulting in poor adsorption capacity and low utilization rate of active sites.In order to overcome these shortcomings,this paper load TiO₂ onto a metal-organic framework with a microporous structure,and the composite photocatalyst exhibits strong adsorption capacity and high photocatalytic performance,resulting on a higher degradation efficiency for indoor pollutants,thus the treatment of HCHO has a potential practical significance.The TiO₂@NH₂-MIL-125 composite catalyst was synthesized by in-situ solvothermal method.The samples were characterized by thermogravimetry,XRD,FT-IR,UV-vis,N₂adsorption/desorption,XPS,Mott-Schottky and electron spin resonance.The photocatalytic activity of TiO₂@NH₂-MIL-125 was evaluated for thee removal of formaldehyde as the target pollutant.The results showed that photocatalytic activity of samples highly depended on the TiO₂ content and method for preparing samples.The optimal catalyst?sample 46TiO₂@54NM in this study,90% of HCHO remval?could effectively degrade HCHO by a factor 6 than pure NH₂-MIL-125?15% of HCHO removal?and the photocatalytic activity remains unchanged after 122 h of photocatalytic reaction under UV irradiation.The excellent photocatalytic performance of TiO₂@NH₂-MIL-125 could be ascribed to the synergistic effect between adsorbability of NH₂-MIL-125 and efficient interfacial charge transfer between TiO₂ and NH₂-MIL-125.In order to study the effect of titanium-based metal organic frameworks prepared by different titanium sources on the photocatalytic activity,this paper prepared TiO₂@NH₂-MIL-125 composites by solvothermal method and the photocatalytic activity for HCHO removal was investigated,and the effects of composite materials prepared by different precursors on morphology and photocatalytic activity were discussed.The results showed that NH₂-MIL-125and TiO₂@NH₂-MIL-125 prepared by using butyl titanate as titanium source showed highest catalytic performance.This is because the NH₂-MIL-125-TBOT had a higher valence band value,thereby having a higher oxidizing power for HCHO removal.Moreover,a certain proportion of and mespore volume are favorable for mass transfer during the reaction,and the photocatalytic activity of the material can be further improved.