Butova Vera V, Zdravkova Videlina R, Burachevskaia Olga A, Tereshchenko Andrei A, Shestakova Pavletta S, Hadjiivanov Konstantin I
Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria.
The Smart Materials Research Institute, Southern Federal University, Rostov-on-Don 344090, Russia.
Nanomaterials (Basel). 2023 May 18;13(10):1675. doi: 10.3390/nano13101675.
Three UiO-66 samples were prepared by solvothermal synthesis using the defect engineering approach with benzoic acid as a modulator. They were characterized by different techniques and their acidic properties were assessed by FTIR spectroscopy of adsorbed CO and CDCN. All samples evacuated at room temperature contained bridging μ-OH groups that interacted with both probe molecules. Evacuation at 250 °C leads to the dehydroxylation and disappearance of the μ-OH groups. Modulator-free synthesis resulted in a material with open Zr sites. They were detected by low-temperature CO adsorption on a sample evacuated at 200 °C and by CDCN even on a sample evacuated at RT. However, these sites were lacking in the two samples obtained with a modulator. IR and Raman spectra revealed that in these cases, the Zr defect sites were saturated by benzoates, which prevented their interaction with probe molecules. Finally, the dehydroxylation of all samples produced another kind of bare Zr sites that did not interact with CO but formed complexes with acetonitrile, probably due to structural rearrangement. The results showed that FTIR spectroscopy is a powerful tool for investigating the presence and availability of acid sites in UiO-66, which is crucial for its application in adsorption and catalysis.
采用缺陷工程方法，以苯甲酸为调节剂，通过溶剂热合成制备了三个UiO-66样品。通过不同技术对它们进行了表征，并通过吸附CO和CDCN的FTIR光谱对其酸性进行了评估。所有在室温下抽空的样品都含有与两种探针分子相互作用的桥连μ-OH基团。在250°C下抽空会导致μ-OH基团脱羟基并消失。无调节剂合成得到了一种具有开放Zr位点的材料。通过在200°C下抽空的样品上进行低温CO吸附以及即使在室温下抽空的样品上通过CDCN都检测到了这些位点。然而，在使用调节剂获得的两个样品中缺乏这些位点。红外光谱和拉曼光谱表明，在这些情况下，Zr缺陷位点被苯甲酸盐饱和，这阻止了它们与探针分子的相互作用。最后，所有样品的脱羟基产生了另一种裸露的Zr位点，这些位点不与CO相互作用，但与乙腈形成络合物，这可能是由于结构重排所致。结果表明，FTIR光谱是研究UiO-66中酸位点的存在和可用性的有力工具，这对其在吸附和催化中的应用至关重要。
