05-O-05-Very open microporous materials: from concept to reality

Cheetham, A. K.; Fjellvg, H.; Gier, Thurman E.; Kongshaug, Kjell Ove; Lillerud, Karl Petter; Stucky, Galen D.

doi:10.1016/s0167-2991(01)81268-4

Cited by 95 publications

(82 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…These results suggested that one way of preparing low framework density zeolites could be to build structures with four-and three-rings. Following this suggestion and the recognition that several beryllium-containing natural zeolites, such as lovdarite and nabesite, have three-rings in their structures, Cheetham et al (6) prepared a large pore (14 × 8 × 8) zeolite with Be that contains three-rings. Previously, Davis et al considered using zinc as a framework cation to promote the formation of three-rings, and while three zincosilicates containing three-rings were subsequently synthesized, none of them contain extra-large pores (7)(8)(9).…”

mentioning

confidence: 99%

Extra-large pore zeolite (ITQ-40) with the lowest framework density containing double four- and double three-rings

Corma

Díaz–Cabañas

Jiang

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

158

132

View full text Add to dashboard Cite

The first zeolite structure (ITQ-40) that contains double four (D4) and double three (D3) member ring secondary building units has been synthesized by introducing Ge and NH 4 F and working in concentrated synthesis gels. It is the first time that D3-Rs have been observed in a zeolite structure. As was previously analyzed [Brunner GO, Meier, WM (1989) Nature 337:146-147], such a structure has a very low framework density (10.1 T∕1,000 Å 3 ). Indeed, ITQ-40 has the lowest framework density ever achieved in oxygen-containing zeolites. Furthermore, it contains large pore openings, i.e., 15-member rings parallel to the [001] hexagonal axis and 16-member ring channels perpendicular to this axis. The results presented here push ahead the possibilities of zeolites for uses in electronics, control delivery of drugs and chemicals, as well as for catalysis.double three-rings in zeolites | low framework density zeolites | germanosilicate zeolites T here is an increasing interest in the synthesis of zeolites with low framework density and extra-large pores (>12 tetrahedral atoms). The preparation of such materials will increase the use of zeolites in catalysis (1, 2) while further expanding their possibilities in microelectronics by preparing materials with low values of the high-frequency dielectric constant, or for uses related with controlled delivery of chemicals and diagnostic treatment (3, 4).In 1989, Brunner and Meier performed a topological analysis on synthesized zeolites and aluminophosphates with four-connected frameworks (5). They found that when the frameworks were grouped as a function of the smallest ring present in the structure, the minimum framework density calculated for each of the groups decreases with the smallest ring size. These results suggested that one way of preparing low framework density zeolites could be to build structures with four-and three-rings. Following this suggestion and the recognition that several beryllium-containing natural zeolites, such as lovdarite and nabesite, have three-rings in their structures, Cheetham et al. (6) prepared a large pore (14 × 8 × 8) zeolite with Be that contains three-rings. Previously, Davis et al. considered using zinc as a framework cation to promote the formation of three-rings, and while three zincosilicates containing three-rings were subsequently synthesized, none of them contain extra-large pores (7-9). Later, we have shown by theoretical and experimental work, that Ge has a directing effect toward the formation of double four-rings (D4Rs) (10, 11), and the presence of these secondary building units (SBUs) has allowed the synthesis of several large and extra-large pore zeolites (12-15). Among those, Instituto de Tecnologia Química number 33 (ITQ-33) contains D4Rs and three-ring units in the structure and has a low framework density (12.3 T∕1;000 Å 3 ). Very recently, an interrupted zeolite with a three-dimensional mesoporous channel system (ITQ-37) has been presented (16), which contains D4Rs and has the lowest framework density reported (10.3 T∕1000...

show abstract

mentioning

confidence: 99%

Extra-large pore zeolite (ITQ-40) with the lowest framework density containing double four- and double three-rings

Corma

Díaz–Cabañas

Jiang

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

158

132

View full text Add to dashboard Cite

show abstract

“…The high levels of beryllium present in the frameworks found in this work, Table 1, leads to OH − :O 2 − ratios greater than unity, such that the stoichiometry of each of these frameworks tends towards a nanoporous polymorph of Be(OH) 2 . In addition a high level of 3Rs in a zeotype structure is known to lead to a low FD, the number of tetrahedral atoms (T) per 1000 Å 3 ; this is exemplified by the beryllosilicate zeotypes OSO and OBW with FDs of 13.3 and 12.7, respectively 23 . Table 1 also summarizes the FDs of the BET, BEE and BOT structures, which show the expected low values.…”

Section: Discussionmentioning

confidence: 99%

“…This presents the intriguing possibility of producing porous zeotype analogues of the stoichiometry 'Be(OH) 2 ' , which, because of the low atomic mass of beryllium, would be of significantly lower density than silicon-based structures; materials of this type should also have extremely high levels of strongly acidic Brönsted acid sites, T-OH-T. Previously reported zeotypes containing some BeO 4 tetrahedra include beryllosilicates, beryllophosphates and beylloarsenates [23][24][25][26] . The majority of these do not demonstrate Be:T' ratios (where T' is Si, P or As) above unity partly because, with oxygen as the bridging anion, the framework would develop a very high negative charge and the bridging oxygen is under-bonded when connected solely to two Be 2 + ions.…”

mentioning

confidence: 99%

Lightweight nanoporous metal hydroxide-rich zeotypes

Littlefield

Weller

2012

Nat Commun

View full text Add to dashboard Cite

nanoporous materials have important industrial applications as molecular sieves, catalysts and in gas separation and storage. They are normally produced as moderately dense silicates (sio 2 ) and aluminosilicates making their specific capacities for the uptake and storage of gases, such as hydrogen, relatively low. Here we report the synthesis and characterization of lightweight, nanoporous structures formed from the metal hydroxide Be(oH) 2 in combination with relatively low levels of framework phosphate or arsenate. Three new zeotype structures are described, constructed mainly of Be(oH) 4 tetrahedra bridged through hydroxide into threemembered rings; these units link together to produce several previously unknown zeotype cage types and some of the most structurally complex, nanoporous materials ever discovered. These materials have very low densities between 1.12 and 1.37 g cm − 3 and theoretical porosities of 63-68% of their total volume thereby yielding very high total specific pore volumes of up to 0.60 cm 3 g − 1 .

show abstract

“…Cheetham et al reported the preparation of a beryllosilicate, being the only one example of a framework containing three-membered rings combined with extra large pores (14-membered rings). [66] The presence of three-membered rings has also been suggested to be advantageous in the quest for crystalline mesoporous materials. [50] The lack of crystallinity, which is a general feature of this class of materials, has been ascribed to their low framework density.…”

Section: Extra-large Pore Zeolitesmentioning

confidence: 99%