最强固体路易斯酸的比较研究：ACF 和 HS-AlF。

Comparative study of the strongest solid Lewis acids known: ACF and HS-AlF.

机构信息

Department of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Straße 2, D-12489 Berlin, Germany.

出版信息

Dalton Trans. 2018 Nov 27;47(46):16461-16473. doi: 10.1039/c8dt03279c.

Abstract

Aluminium chlorofluoride (ACF) and high-surface aluminium fluoride (HS-AlF3) were analyzed by a set of characterization methods to assess their acidic properties: NH3-TPD, CO adsorption followed by DRIFTS, CD3CN-PAS-FTIR and MAS NMR spectroscopy after 15N-pyridine adsorption. Both catalysts contain very strong and medium-strong Lewis acid sites as confirmed by CO adsorption, in which small differences arise from the morphological properties of each catalyst, with ACF being microporous and HS-AlF3 mesoporous. Shifts of the CO vibration band of up to 77 cm-1 were observed, which account for very strong Lewis acid sites. In addition, very strong Lewis acid sites could be identified by CD3CN-PAS for both catalysts, exhibiting a shift of 95 cm-1 from free nitrile, the highest ever reported for a solid Lewis acid.

摘要

采用一系列的表征方法对氯化铝氟 (ACF) 和高比表面积氟化铝 (HS-AlF3) 进行分析，以评估它们的酸性性质：NH3-TPD、CO 吸附后 DRIFTS、15N-吡啶吸附后的 CD3CN-PAS-FTIR 和 MAS NMR 光谱。两种催化剂都含有非常强和中强的路易斯酸位，这一点通过 CO 吸附得到了证实，其中，每个催化剂的形态特性会产生细微的差异，ACF 为微孔，HS-AlF3 为介孔。观察到 CO 振动带的移动高达 77cm-1，这表明存在非常强的路易斯酸位。此外，两种催化剂都可以通过 CD3CN-PAS 识别出非常强的路易斯酸位，其特征是从游离腈的 95cm-1 位移，这是迄今为止在固体路易斯酸中报道的最高值。