Vapor-Phase Strategy to Pillaring of Two-Dimensional Zeolite

Abstract

Two-dimensional (2D) layered zeolites are new forms of 3D zeolite frameworks. They can be pillared to form more open porous structures with increased access for reactants that are too big for the micropores of zeolites. The current pillaring procedure, however, requires intercalation of pillaring precursors by dispersing 2D zeolite in an alkoxide liquid and hydrolizing entrapped alkoxide to form inorganic oxide pillars in an aqueous alkaline solution. Both steps use excess solvents, generate significant waste, and require multiple synthesis and separation steps. Here we report a vapor-phase pillarization (VPP) process to produce pillared zeolites from 2D layered zeolite structures. The VPP process has ∼100% efficiency of alkoxide usage in the intercalation step, requires less (and, in some cases, zero) water addition in the hydrolysis step, does not require separation for product recovery, and generates no liquid waste. Furthermore, synthesis of pillared zeolites via the VPP process can be accomplished within a single apparatus with one-time operation. The pillared zeolite prepared by the VPP method preserved the zeolitic layered structure as well as acidity and showed enhancement in catalytic alkylation of mesitylene with benzyl alcohol compared to 2D layered zeolite without pillarization treatment.

Two-Dimensional Zeolite Materials: Structural and Acidity Properties

“…In 2017, Fan's group reported the exfoliation of multilamellar MFI by suspending the layered zeolite precursors in telechelic liquid polybutadiene followed by brief shearing or sonication at room temperature [20]. The intercalation of TEOS into the multilamellar MFI zeolites followed by hydrolysis has been used to produce SiO 2 -pillared MFI [35,179]. Other metal oxide pillared cases have also been reported, such as titanosilicate [42], magnesium oxide, zinc oxide [180], and tin-silica [176].…”

Enhanced Surface Activity of MWW Zeolite Nanosheets Prepared via a One-Step Synthesis

“…32 Recently, Liu et al developed a novel vapor-phase pillarization (VPP) process to produce pillared 2D zeolite materials with ∼100% efficiency. 33 Interestingly, postsynthetic processes have been extended to borosilicates, where single-step exfoliation along with isomorphous substitution of boron with aluminum has been demonstrated on ERB-1 (MWW type; borosilicate counterpart). 34 Exfoliation has also been used in related processes referred to as ADOR (assembly−disassembly−organization− reassembly) to construct new frameworks.…”

“…Roth et al obtained the first pillared zeolitic material, MCM-36, where swollen layers are intercalated by silica species . Recently, Liu et al developed a novel vapor-phase pillarization (VPP) process to produce pillared 2D zeolite materials with ∼100% efficiency . Interestingly, postsynthetic processes have been extended to borosilicates, where single-step exfoliation along with isomorphous substitution of boron with aluminum has been demonstrated on ERB-1 (MWW type; borosilicate counterpart) .…”

Few‐Unit‐Cell MFI Zeolite Synthesized using a Simple Di‐quaternary Ammonium Structure‐Directing Agent

“…Zeolites composed of one‐ to few‐unit‐cell domains,[ 1 , 2 , 3 , 4 ] exhibit distinct, and for some uses superior, catalytic and adsorption performance compared to conventional zeolites. [ 5 , 6 , 7 , 8 , 9 , 10 ] In this context, the quest for synthetic methods to minimize the size of crystalline zeolitic domains while accomplishing their arrangement to form hierarchical porous materials and thin film membranes persists. [11] Of particular importance is the synthesis of MFI with crystalline domains on the order of one to few unit cells (ca.…”