Targeted Synthesis of Two Super‐Complex Zeolites with Embedded Isoreticular Structures

Abstract

The reagents used for zeolite syntheses included tetraethylammonium bromide (TEABr, 98%, Aldrich), NaOH (50% aqueous solution, Aldrich), Ca(NO3)2·4H2O (98%, DC Chemical), aluminum hydroxide (Al(OH)3•1.0H2O (Aldrich), colloidal silica (Ludox AS-40, DuPont), and deionized water. The final composition of the synthesis mixture was 5.2TEABr·1.9Na2O·0.5Ca(NO3)2·xAl2O3·7.2SiO2·yH2O, where x and y are varied between 0.5 ≤ x ≤ 1.5 and 150 ≤ y ≤ 390, respectively. After being stirred at 80 °C for 24 h, the synthesis mixture was charged into Teflon-lined 23-mL autoclaves and heated to 145 °C under rotation (60 rpm) for 2 days. The solid products were recovered by filtration, washed repeatedly with water, and then dried overnight at room temperature. Materials CharacterizationPowder X-ray diffraction (XRD) patterns were recorded on a PANalytical X´Pert diffractometer (Cu Kα radiation) with an X´Celerator detector. Data were collected with a fixed divergence slit (0.50°) and Soller slits (incident and diffracted = 0.04 rad). Crystal morphology and average size were determined by a JEOL JSM-6510 scanning electron microscope (SEM). The CO2, CH4, and N2 adsorption isotherms were measured at 25 °C and at pressures up to 1.2 bar using a Mirae SI nanoPorosity-XG analyzer. Prior to the experiments, zeolite sample was evacuated at 250 °C for 6 h.Synchrotron powder XRD data for the solid product (a mixture of PST-25, PST-26, and PST-28) obtained from Run 8 in Table 1 were collected on the 9B beamline equipped with a ceramic furnace of the Pohang Acceleration Laboratory (PAL; Pohang, Korea) using monochromated X-rays (λ = 1.4865 Å). The detector arm of the vertical scan diffractometer consists of seven sets of Soller slits, flat Ge(111) crystal analyzers, anti-scatter baffles, and scintillation detectors, with each set separated by 20°. Data were obtained on the sample at room temperature in flat plate mode, with a step size of 0.01° and an overlap of 0.50° to the

Automated serial rotation electron diffraction combined with cluster analysis: an efficient multi-crystal workflow for structure determination

“…We attribute this to the huge differences in reflection intensities and the large fraction of reflections with practically zero intensities because of the presence of common building units in the structures. This phenomenon has previously been identified as one of the limiting factors for direct structure solution for these and related materials (Guo et al, 2015;Shin et al, 2016).…”

Supramolecular Organization in Confined Nanospaces

“…Some natural zeolites exhibit chirality (goosecreekite) or extraordinary structural complexity, like paulingite (Figure ). A recently synthesized zeolite family was modeled upon paulingite, and key for the synthesis was the recognition that Mg and Ca cations – found in related zeolite minerals – could be used as auxiliary templating agents for the more complex members of the family …”

Structural characterisation of complex zeolite structures using electron crystallography

“…By analysing the strong reflection distributions and the weak diffraction spots between the experimental and simulated electron diffraction patterns, the structures of as-synthesized PST-26 (Im-3m, a = 75 Å) and PST-28 (Im-3m, a = 85 Å) were successfully verified. 1 This work not only demonstrated the power of electron crystallography, but also shows the possibility to combine cryo-EM and electron diffraction techniques to study electron beam sensitive materials with complex structures such as micro-sized protein crystals.…”

“…Rotation electron diffraction (RED) was thus developed with the aim of accurate determination of 3D atomic structures of crystals of sub-micrometer sizes [1][2]. RED has shown to be powerful in phase identification and structure determination.…”

“…1 The prediction of these two structures was achieved by the strong reflections approach 2 and model building, which provided essential information for targeted syntheses of these materials. 3 Due to small energy differences, PST-26 and PST-28 could only be obtained as mixtures, together with a small amount of gismondine which makes structure confirmation by powder X-ray diffraction more difficult.…”