Graphical Sheet-like zeolite TS-1 was synthesized under hydrothermal conditions by adding seed and urea. Liquid seed and pre-crystallization could adjust thickness of sheet-like sample in b-axis direction. Epoxidation of 1-hexene with H 2 O 2 catalyzed by sheet-like TS-1 gave high selectivity of 1,2-epoxyhexane. In zeolite TS-1, the straight channel parallelled to the b-axis direction has larger pore size and thus is main diffusion channel for molecules. Shorter b-axis brings about shorter diffusion channel, which can leads to higher adsorption and diffusion rate. Therefore, with regard to the morphology modification of MFI zeolites, many studies touch on short b-axis zeolites have been reported. Unfortunately, most of the preparation processes require harsh synthesis conditions and complex organic templates, and they are not conducive to large-scale applications. In this work, cheap organic additive urea and seed crystals were added to synthesize sheet-like TS-1, which boasts short b-axis. At the same time a pre-crystallization was performed at the aging solution stage. In the b-axis direction, the zeolite TS-1 prepared in this way had a minimum thickness of about 50 nm. This is because urea can inhibit the growth of crystals in the b-axis direction, and the guiding effect of the seed liquid also plays the function of adjusting the b-axis thickness. In the epoxidation of 1-hexene with H 2 O 2 when catalyzed by sheet-like TS-1, the selectivity of the target product 1,2-epoxyhexane was significantly improved.
Freeze-casting (ice templating) is generally used to prepare super-macroporous materials. However, water solubility limits the application of freeze-casting in hydrophobic material fabrication. In the present work, inexpensive and low-toxic sulfolane was used as a novel crystallization-induced porogen (sulfolane crystal templating) to prepare super-macroporous hydrophobic monoliths (cryogels) with tunable polarity. The phase transition of sulfolane consisted of reversible processes in the liquid, semi-crystalline, and crystalline states. Because of the density change during phase transition, liquid sulfolane experienced a 16.4% volume shrinkage per unit mass. Thus, the cryogels obtained using the conventional freezing method contained obvious hollow-shaped defects. Furthermore, a novel route of pre-cooling, pre-crystallization, crystal growth, freezing, and thawing (PPCFT) was employed to prepare cryogels with defect-free macroscopic morphology and uniform pore structure. The as-obtained cryogels were composed of a super-macroporous structures and interconnected channels, and their porosity ranged between 85 and 97%. Moreover, the cryogels manifested good hydrophobicity (contact angle = 120–130°) and had absorption capacities greater than 10 g g–1 for oils and organic liquids. The maximum absorption capacities of the resultant cryogels in dichloromethane, ethyl acetate, and liquid paraffin were 60.3, 35.8, and 15.2 g g–1, respectively. Moreover, sulfolane could conveniently dissolve hydrophobic and hydrophilic monomers to generate amphiphilic cryogels (contact angle = 130–0°). Therefore, sulfolane crystal templating is a potential fabrication method for super-macroporous hydrophobic materials with tunable polarity.
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