The Synthesis of an Extra‐Large‐Pore Zeolite with Double Three‐Ring Building Units and a Low Framework Density

Abstract

Zeolites are crystalline inorganic solids formed by TO 4 tetrahedra (T = Si, P, Al, Ge, etc.) with a well-defined system of regular pores having diameters up to about 2 nm. [1,2] The possibility of tuning pore dimensions and framework compositions have made zeolites the most successful materials for applications in gas adsorption and separation and for catalysis. [3,4] Their uses have been further expanded [3] to microelectronics for preparing materials with low values of the high-frequency dielectric constant [5] or manufacturing encapsulated light-emitting devices (LEDs), [6] to medicine for diagnostic treatments [7] and controlled drug delivery, or for release of semiotics for controlling insect populations in agricultural uses. [8] Those applications often require structures with low framework densities, large internal volumes, and preferentially, extra-large pores. However, up to now, the number of known zeolites with a low framework density (FD 12) is almost negligible, and the number with extra-large pores (! 18-R) is also extremely small. [1] Computational methods can predict a large number of thermodynamically feasible new structures, and they can stimulate and inspire the discovery of new structures. [9][10][11] For example, Foster and Treacy [10] have used a symmetry-constrained intersite bond searching method and have generated more than two million structures. With that methodology, the authors predicted a series of thermodynamically feasible extra-large-pore zeolites. Deem et al. [11] have also modeled relatively large number of low density zeolites and were able to show that the low-energy and low-density materials also tend to have desirably large rings.Among the zeolite structures with extra large pores predicted by Foster and Treacy, there is one with 18 10 10-R pore topology that could be of particular interest for catalysis, as it combines an extra-large pore (18-R) for molecular accessibility with connected 10-R pores that can introduce shape-selectivity effects. Recently, the predicted zeolite was synthesized and named ITQ-33. [12] This zeolite has 3-R and D4R units in the structure, and was at the time the silicate-based zeolite with the lowest framework density (12.3.T/1000 3 ). The pore topology of this extra-large-pore zeolite presented quite unique and interesting catalytic properties: The pore accessibility to large molecules through the 18-R was combined with shape selectivity in the 10-R pores for the primary products formed. [13] In the same data base, Foster and Treacy also predicted an extra-large-pore zeolite that was closely related to ITQ-33 (Zeolite reference 191_4_1985). In that new structure, the 10-R pores of ITQ-33 were expanded to 12-R pores connecting the larger perpendicular 18-R channels. The result was a zeolite with 18 12 12 pore topology instead of the 18 10 10 for ITQ-33. In particular, along with D4R units, the new zeolite contains D3R units that have never been seen in synthesized zeolites, which could be related to geometric strains introduced in the framework ...

An Extra‐Large‐Pore Zeolite with 24×8×8‐Ring Channels Using a Structure‐Directing Agent Derived from Traditional Chinese Medicine

“…[1] So far,afew extra-large-pore zeolites with different framework compositions have been synthesized, such as aluminophosphates/gallophosphates (VPI-5, [2] AlPO 4 -8, [3] cloverite, [4] ITQ-51 [5] ), pure silicates (UTD-1, [6] ), substituted (except Ge) silicates (OSB-1, [8] SSZ-53, SSZ-59, [9] ECR-34, [10] SSZ-61, [11] EMM-23 [12] )a nd germanosilicates (ITQ-15, [13] ITQ-33, [14] ITQ-37, [15] ITQ-40, [16] ITQ-43, [17] ITQ-44, [18] ITQ-54 [19] and NUD-1 [20] ). The framework structure was solved and refined using continuous rotation electron diffraction (cRED) data from nanosized crystals.SYSU-3 exhibits anew zeolite framework topology,w hich has the first 24 8 8-ring extra-largepore system and af ramework density (FD) as low as 11.4 T/ 1000 3 .T he unique skeleton of the OSDAp laysa ne ssential role in the formation of the distinctive zeolites tructure.T his work provides an ew perspective for developing new zeolitic materials by using alkaloids as cost-effective OSDAs.…”

“…[1] So far,afew extra-large-pore zeolites with different framework compositions have been synthesized, such as aluminophosphates/gallophosphates (VPI-5, [2] AlPO 4 -8, [3] cloverite, [4] ITQ-51 [5] ), pure silicates (UTD-1, [6] ), substituted (except Ge) silicates (OSB-1, [8] SSZ-53, SSZ-59, [9] ECR-34, [10] SSZ-61, [11] EMM-23 [12] )a nd germanosilicates (ITQ-15, [13] ITQ-33, [14] ITQ-37, [15] ITQ-40, [16] ITQ-43, [17] ITQ-44, [18] ITQ-54 [19] and NUD-1 [20] ). [1] So far,afew extra-large-pore zeolites with different framework compositions have been synthesized, such as aluminophosphates/gallophosphates (VPI-5, [2] AlPO 4 -8, [3] cloverite, [4] ITQ-51 [5] ), pure silicates (UTD-1, [6] ), substituted (except Ge) silicates (OSB-1, [8] SSZ-53, SSZ-59, [9] ECR-34, [10] SSZ-61, [11] EMM-23 [12] )a nd germanosilicates (ITQ-15, [13] ITQ-33, [14] ITQ-37, [15] ITQ-40, [16] ITQ-43, [17] ITQ-44, [18] ITQ-54 [19] and NUD-1 [20] ).…”

Rigid/Flexible Organic Structure Directing Agents for Directing the Synthesis of Multipore Zeolites: A Computational Approach

“…4 The presence of those small cages do not define the full zeolitic framework topology by themselves, but as we have reported in the last years, the presence of Ge atoms systematically allowed the crystallization of extra-large pore zeolites with pores larger than 10 Å. [5][6][7][8][9] These results are in clear agreement with the predictions performed by Brunner and Meier, who proposed that structures with large amount of 4-and 3-rings in their structure would present low framework densities (FD, measured as T-atoms/1000 Å 3 ), and consequently, large void volume or very open structures. 10 On the other hand, it is broadly described in the literature that the size, shape and rigidity of the organic molecules introduced in the synthesis gels acting as structure directing agents (SDAs), clearly influence the pore topology of the crystallized zeolites.…”

Toward Greener and Designed Synthesis of Zeolite Materials

“…Because of the flexible GeOGe or SiOGe angles, the introduction of Ge can stabilize the formation of D4R. Notably, with the preferential occupancy of germanium, ITQ-44 [6] was successfully synthesized which contains not only D4Rs but also the unusual D3Rs. A series of novel D4R-containing extra-large pore germanosilicates have been successfully prepared with designed organic SDAs and F − ions in concentrated gels.…”