The layered silicate COK-5 has been used for an interlayer expansion reaction with dichlorodimethylsilane (DCDMS) at 180 °C to interconnect neighboring layers, yielding a new and crystalline microporous framework. The samples containing the methyl functional groups in the as-made form and having OH groups in the calcined form were designed as COE-5 and calcined COE-5. These samples were characterized with X-ray diffraction (XRD), N 2 sorption isotherms, inductively coupled plasma optical emission spectrometry (ICP-OES), infrared spectroscopy (IR), high-resolution transmission electron micrograph (HRTEM), thermogravimetry-differential thermal analysis (TG-DTA), and 29 Si and 13 C solid-state magic-angle spinning nuclear magnetic resonance (MAS NMR), as well as the contact angle techniques. XRD patterns and HRTEM images suggest that the sample interlayer spacing has been expanded by nearly 0.5 Å. The N 2 sorption isotherms of the materials show the BET surface areas are 165 m 2 /g for COE-5 and 340 m 2 /g for calcined COE-5. 29 Si and 13 C MAS NMR as well as IR spectroscopy confirm the insertion of the linker group -Si(CH 3 ) 2 - connecting neighboring layers. Interestingly, calcined COE-5 shows enhanced catalytic performance in the acetalisation of glycerol with acetone to produce solketal, compared with COK-5.
In the interlayer expansion of the layered zeolite precursor COK-5, a Sn, salt, bis(2,4-pentanedionate)-dichlorotin [Sn(acac) 2 Cl 2 ], instead of a silylating agent was used to link the layers at 180 °C. The obtained material, which is designed as Sn-COE-5, shows a shift of the first XRD reflection, which is very similar to that of COK-5 interlayer expanded with dichlorodimethylsilane (DCDMS), indicating an increase in interlayer distance . X-ray diffraction (XRD), N 2 sorption isotherms, inductively coupled plasma (ICP), and X-ray photoelectron spectroscopy (XPS) support the incorporation of isolated Sn sites in the sample. In the conversion of glucose to levulinic acid, Sn-COE-5 exhibits much higher activity than COK-5, which is due to the presence of Lewis acidic sites in the Sn-COE-5.
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