Synthetic Control of the Defect Structure and Hierarchical Extra-Large-/Small-Pore Microporosity in Aluminosilicate Zeolite SWY

The SWY-type aluminosilicate zeolite, STA-30, has been synthesized via different routes to understand its defect chemistry and solid acidity. The synthetic parameters varied were the gel aging, the Al source, and the organic structure directing agent. All syntheses give crystalline materials with similar Si/Al ratios (6–7) that are stable in the activated K,H-form and closely similar by powder X-ray diffraction. However, they exhibit major differences in the crystal morphology and in their intracrystalline porosity and silanol concentrations. The diDABCO-C82+ (1,1′-(octane-1,8-diyl)bis(1,4-diazabicyclo[2.2.2]octan)-1-ium)-templated STA-30 samples (but not those templated by bisquinuclidinium octane, diQuin-C82+) possess hierarchical microporosity, consisting of noncrystallographic extra-large micropores (13 Å) that connect with the characteristic swy and gme cages of the SWY structure. This results in pore volumes up to 30% greater than those measured in activated diQuin-C8_STA-30 as well as higher concentrations of silanols and fewer Brønsted acid sites (BASs). The hierarchical porosity is demonstrated by isopentane adsorption and the FTIR of adsorbed pyridine, which shows that up to 77% of the BASs are accessible (remarkable for a zeolite that has a small-pore crystal structure). A structural model of single can/d6r column vacancies is proposed for the extra-large micropores, which is revealed unambiguously by high-resolution scanning transmission electron microscopy. STA-30 can therefore be prepared as a hierarchically porous zeolite via direct synthesis. The additional noncrystallographic porosity and, subsequently, the amount of SiOHs in the zeolites can be enhanced or strongly reduced by the choice of crystallization conditions.

Partial interzeolite conversion synthesis product without the use of seeds Figure S1. PXRD pattern of the product of the seed-free partial interzeolite conversion gel composition used for the synthesis of STA-30.
Gel compositions, reagent sources and synthesis conditions

Synthesis of aluminosilicate OFF sample
The synthesis was based on the work carried out by Łukaszuk et al. 3 Sodium hydroxide, potassium hydroxide and water were mixed and then heated up to 348 K.
Aluminium isopropoxide was added and the mixture was stirred for 15 min after which the heating was stopped. The solution was added to Ludox HS-40, and the mixture was left to stir for minimum 30 min. TMACl was then added and the mixture was allowed to stir for a final hour. The gel composition was 0.04 Al2O3 : 1.0 SiO2 : 0.57 NaOH : 0.14 KOH : 0.02 TMACl : 11.3 H2O. The gel was transferred into a stainless-steel autoclave equipped with a Teflon liner and heated for 8 days at 373 K. The resulting solid was filtered and washed with DI water until the filtrate had a neutral pH. The solid was dried in a 338 K oven overnight.
The Si/Al of the product, as characterised by EDS was 3.3.   Ar adsorption isotherms at 87 K of SWY, ERI and OFF aluminosilicate materials Figure S8. Ar adsorption/desorption isotherms measured at 87 K on the H-forms of TPA_AliPr, TPA_diQuin-C8, ERI and OFF (left, insert shows an enlarged view of 10 -7 -0.1 p/po). The DFT and HK pore size distributions are also plotted (top right and bottom right). 11.9 11.9 ± 0.7 Additional FTIR spectra Figure S9. Difference FTIR spectra between the spectrum of dehydrated TPA_AliPr_H and spectra collected at temperatures between 423 K and 723 K after the structure had been loaded with NH3 (left) and the variation of the intensity of the peaks that show the interaction between NH3 and the zeolite acid sites.

Silica to Alumina ratio (SAR) by XRF and NMR
FTIR spectra of SWY, ERI and OFF aluminosilicate materials Figure S10. SiOH region of the FTIR spectra of the H-forms of TPA_AliPr, TPA_diQuin-C8, ERI and OFF, after dehydration (left) and difference FTIR spectra between the aforementioned data and the spectra of the samples upon pyridine (Py) adsorption at 473 K (right). Absorbance values were normalized, and spectra were offset for ease of visualisation. Figure S11. Py region of the difference FTIR spectra between the spectra of the dehydrated samples (H-forms of TPA_AliPr, TPA_diQuin-C8, ERI and OFF) and the spectra of the samples upon pyridine adsorption at 473 K. Absorbance values were normalised and spectra were offset for ease of visualisation. For a sample that is theoretically made up of a fraction of ideal SWY unit cells (considered below as an ideal 221 SWY supercell) and a fraction, fvacancies, of 221 SWY supercells with removed can columns, the total uptake is made up of: The experimental uptake at 0.5 relative pressure for TPA_AliPr_H was 241.4 cm 3 g -1 . By using this number in the relationship above, the fraction of ideal unit cells and 2×2×1 supercells with vacancies are: .
If ~36% of the structure of TPA_AliPr_H is described by the 221 supercell with a column of can/d6r cages removed and 3 columns intact, and the rest of the structure is described by the ideal unit cell, this means that ~9% of can/d6r cages have to be removed to introduce the additional porosity observed in TPA_AliPr_H.
The experimental uptake at 0.5 relative pressure for OSDA_Y_H was 212.3 cm 3 g −1 . By plugging this number into the total uptake equation, the fraction of ideal unit cells and 221 supercells with vacancies are: .
If ~12% of the structure of OSDA_Y_H is described by the 221 supercell with a column of can/d6r cages removed and 3 columns intact, and the rest of the structure is described by the ideal unit cell, this means that ~3% of can/d6r cages have to be removed to introduce the additional porosity observed in OSDA_Y_H.
FTIR spectra of the interaction of TPA_AliPr_H with pyridine and collidine Figure S14. SiOH region of FTIR spectrum of TPA_AliPr_H dehydrated at 723 K and offset difference spectra showing the interaction between TPA_AliPr_H with pyridine (red outline) and collidine (pink outline). Absorbance values were normalized, and spectra were offset for ease of visualisation.