Roth Wieslaw J, Gil Barbara, Mayoral Alvaro, Grzybek Justyna, Korzeniowska Aleksandra, Kubu Martin, Makowski Wacław, Čejka Jiří, Olejniczak Zbigniew, Mazur Michal
Faculty of Chemistry, Jagiellonian University in Kraków, Gronostajowa 2, 30-387 Kraków, Poland.
Dalton Trans. 2018 Feb 27;47(9):3029-3037. doi: 10.1039/c7dt03718j.
Layered zeolite materials with FER layer topology can produce various condensed and expanded structures including zeolite frameworks, FER and CDO, their interlayer expanded forms (IEZ), and organic-intercalated and pillared derivatives. This work concerns pillaring of the surfactant-swollen derivative with a gallery height of ca. 2.5 nm between layers by treatment with tetraethylorthosilicate (TEOS) at room and elevated temperatures. The materials obtained at 100 °C and higher showed unusual properties including 2 nm pores on the micro/mesoporous border and disordered layer packing indicated by the absence of distinct low angle interlayer peaks at d-spacing >3 nm (∼3° 2θ Cu Kα radiation) in the X-ray diffraction pattern (XRD). TEOS treatment at room temperature produced a pillared molecular sieve with the expected mesoporous characteristics, namely a pore size of around 3 nm and a high intensity low angle (001) peak at 2.3° 2θ, and a d-spacing of 3.8 nm, in the XRD. The characterization aiming to elucidate the nature of the obtained unusual products included gas adsorption isotherms, aberration corrected (C-corrected) Scanning Transmission Electron Microscopy (STEM) studies and Si solid state NMR. BET surface area values decreased with the temperature of TEOS treatment from approximately 1200 m g to ∼900 and 600 m g, at room temperature, 100 °C, and 120 °C, respectively. The Si solid state NMR revealed the presence of both Q ((SiO)SiOX, X = H or minus charge) and Q ((SiO)Si) centers giving separated signals up to the pillaring step. After pillaring at 100 °C and calcination, the nominal intensity ratios Q : Q were 2.17 and 2.61 but the signals were merged into one broad peak indicating the structural heterogeneity of Si-O coordination. The microscopy showed the presence of FER layers in the samples but the overall structure and composition were not well-defined. The observed unusual disorganization and possible partial degradation of layers during pillaring may result from the combination of high temperature, alkalinity (surfactant hydroxide) and siliceous composition of the layers. The obtained pillared products are of interest for the preparation of larger pore catalysts and sorbents or controlled drug delivery.
具有FER层拓扑结构的层状沸石材料可以产生各种凝聚和膨胀结构，包括沸石骨架、FER和CDO、它们的层间膨胀形式（IEZ）以及有机插层和柱撑衍生物。这项工作涉及通过在室温和高温下用正硅酸四乙酯（TEOS）处理，对层间间距约为2.5 nm的表面活性剂溶胀衍生物进行柱撑。在100°C及更高温度下获得的材料表现出异常特性，包括微/介孔边界处2 nm的孔以及X射线衍射图谱（XRD）中d间距>3 nm（约3°2θ Cu Kα辐射）处没有明显的低角度层间峰所表明的无序层堆积。室温下的TEOS处理产生了具有预期介孔特性的柱撑分子筛，即孔径约为3 nm，在2.3°2θ处有高强度低角度（001）峰，XRD中的d间距为3.8 nm。旨在阐明所得异常产物性质的表征包括气体吸附等温线、像差校正（C校正）扫描透射电子显微镜（STEM）研究和Si固体核磁共振。BET表面积值随着TEOS处理温度的降低而降低，在室温、100°C和120°C下分别从约1200 m²/g降至约900 m²/g和600 m²/g。Si固体核磁共振显示，在柱撑步骤之前，Q（(SiO)SiOX，X = H或负电荷）和Q（(SiO)Si）中心均存在，给出分离的信号。在100°C下柱撑并煅烧后，名义强度比Q¹：Q²分别为2.17和2.61，但信号合并为一个宽峰，表明Si - O配位的结构不均匀性。显微镜观察表明样品中存在FER层，但整体结构和组成不明确。在柱撑过程中观察到的异常无序和可能的层部分降解可能是由高温、碱性（表面活性剂氢氧化物）和层的硅质组成共同作用的结果。所得的柱撑产物对于制备更大孔径的催化剂、吸附剂或可控药物递送具有重要意义。
