U.S. patent application number 17/130220 was filed with the patent office on 2021-04-15 for adsorbent-assisted stabilization of highly reactive gases.
The applicant listed for this patent is NUMAT TECHNOLOGIES, INC.. Invention is credited to Jose ARNO, Omar K. FARHA, Paul Wai-Man SIU, Glenn M. TOM, Ross VERPLOEGH.
Application Number | 20210106940 17/130220 |
Document ID | / |
Family ID | 1000005300224 |
Filed Date | 2021-04-15 |
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United States Patent
Application |
20210106940 |
Kind Code |
A1 |
TOM; Glenn M. ; et
al. |
April 15, 2021 |
ADSORBENT-ASSISTED STABILIZATION OF HIGHLY REACTIVE GASES
Abstract
A method of adsorbing a highly reactive gas onto an adsorbent
material comprising adsorbing the highly reactive gas to the
adsorbent material. The absorbent material comprises at least one
Lewis basic functional group, or pores of a size to hold a single
molecule of the highly reactive gas, or inert moieties which are
provided to the adsorbent material at the same time at the same
time as the highly reactive gas, prior to adsorbing the highly
reactive gas or after adsorbing the highly reactive gas, or the
highly reactive gas reacts with moieties of the adsorbent material
resulting in passivation of the adsorbent material. A rate of
decomposition of the adsorbed highly reactive gas is lower than a
rate of decomposition for the neat gas at equal volumetric loadings
and equal temperatures for both the adsorbed highly reactive gas
and the neat gas.
Inventors: |
TOM; Glenn M.; (Bethany
Beach, DE) ; SIU; Paul Wai-Man; (Evanston, IL)
; ARNO; Jose; (Portland, OR) ; FARHA; Omar K.;
(Morton Grove, IL) ; VERPLOEGH; Ross; (Buffalo
Grove, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NUMAT TECHNOLOGIES, INC. |
Skokie |
IL |
US |
|
|
Family ID: |
1000005300224 |
Appl. No.: |
17/130220 |
Filed: |
December 22, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16139958 |
Sep 24, 2018 |
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17130220 |
|
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62562718 |
Sep 25, 2017 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B01D 2257/204 20130101;
B01J 20/226 20130101; B01D 2253/102 20130101; B01D 53/02 20130101;
B01J 20/20 20130101; B01D 2257/93 20130101; B01D 2253/25 20130101;
B01D 2253/204 20130101; B01D 2257/40 20130101; B01D 53/0415
20130101; B01D 2257/553 20130101; B01J 20/28078 20130101; F17C
11/00 20130101; B01D 2253/308 20130101 |
International
Class: |
B01D 53/02 20060101
B01D053/02; B01J 20/20 20060101 B01J020/20; B01J 20/22 20060101
B01J020/22; B01D 53/04 20060101 B01D053/04; F17C 11/00 20060101
F17C011/00; B01J 20/28 20060101 B01J020/28 |
Claims
1. A method of adsorbing a highly reactive gas onto a metal-organic
framework (MOF) comprising: providing the highly reactive gas to
the MOF, wherein the gas and the MOF form a labile Lewis acid-base
adduct which lowers a rate of decomposition of the highly reactive
gas relative to a rate of decomposition of the neat highly reactive
gas at the same temperature and same volumetric loadings.
2. The method of claim 1, wherein the highly reactive gas acts as
an electron donor Lewis base.
3. The method of claim 2, wherein the Lewis base is a heterocyclic
molecule selected from 5 or 6 member rings having 1-3 non-carbon
atoms.
4. The method of claim 1, wherein the highly reactive gas acts as
an electron acceptor Lewis acid.
5. The method of claim 1, wherein the adsorbed highly reactive gas
is arsine (AsH.sub.3), stibine (SbH.sub.3), phosphine (PH.sub.3),
borane (BH.sub.3), diborane (B.sub.2H.sub.6), halides, germane,
digermane, silane, disilane, hydrazine or nitrogen trifluoride.
6. A method of adsorbing a highly reactive gas onto a metal-organic
framework (MOF) comprising: providing the highly reactive gas to
the MOF, wherein, the pores of the MOF are sized to hold one
molecule of the highly reactive gas.
7. The method of claim 6, wherein the adsorbed highly reactive gas
is arsine (AsH.sub.3), stibine (SbH.sub.3), phosphine (PH.sub.3),
borane (BH.sub.3), diborane (B.sub.2H.sub.6), halides, germane,
digermane, silane, disilane, hydrazine or nitrogen trifluoride.
8. A method of adsorbing a highly reactive gas onto a metal-organic
framework (MOF) comprising: reacting a fluid different from the
highly reactive gas with the adsorbent material, wherein the fluid
passivates the adsorbent such that a rate of decomposition of the
reactive adsorbed gas is lower than a rate of decomposition for the
neat gas at equal volumetric loadings and equal temperatures for
both adsorbed gas and neat gas; and adsorbing the highly reactive
gas to the MOF.
9. The method of claim 8, further comprising removing byproducts
formed by the reaction of the fluid with the MOF prior to adsorbing
the highly reactive gas to the MOF.
10. The method of claim 8, further comprising raising at least one
of temperature or pressure to accelerate passivation of the
MOF.
11. The method of claim 8, wherein the fluid comprises a strong
oxidizer or a reducing agent.
12. The method of claim 8, wherein: the oxidizer comprises oxygen,
chlorine, fluorine, or hydrogen peroxide; and the reducing agent
comprises hydrogen, ammonia or sulfur dioxide.
13. A method of adsorbing a highly reactive gas onto an adsorbent
material comprising: adsorbing a highly reactive gas to the
adsorbent material; and adsorbing inert moieties to the absorbent
material at the same time as the highly reactive gas, prior to
adsorbing the highly reactive gas or after adsorbing the highly
reactive gas, wherein a rate of decomposition of the adsorbed
highly reactive gas is lower than a rate of decomposition for the
neat gas at equal volumetric loadings and equal temperature for
both the adsorbed highly reactive gas and neat gas.
14. The method of claim 13, wherein the adsorbent material
comprises a MOF, a porous carbon, a POP, or combinations
thereof.
15. The method of claim 13, wherein the highly reactive gas is
arsine (AsH.sub.3), borane (BH.sub.3), diborane (B.sub.2H.sub.6),
phosphine (PH.sub.3), stibine (SbH.sub.3), halide, germane,
digermane, silane, disilane, hydrazine, or nitrogen
trifluoride.
16. The method of claim 13, wherein the inert moieties do not
chemically react with the highly reactive gas.
17. The method of claim 16, wherein the inert moieties comprise
helium, nitrogen, aliphatic alkanes that comprise only of carbon
and hydrogen atoms, aromatic rings that comprise only of carbon and
hydrogen atoms, or combinations thereof.
18. The method of claim 17, wherein the highly reactive gas is
diborane.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 16/139,958, filed Sep. 24, 2018, which claims the benefit of
U.S. Provisional Application No. 62/562,718, filed Sep. 25, 2017,
both are hereby incorporated by reference in their entirety.
FIELD
[0002] The present invention is directed to the adsorption-based
storage of highly reactive gases which provide stabilization and
lowers the rate of gas decomposition and in-situ impurity
generation. As an example, the embodiments are directed toward the
stabilization of highly reactive gases including arsine
(AsH.sub.3), phosphine (PH.sub.3), stibine (SbH.sub.3), borane
(BH.sub.3), diborane (B.sub.2H.sub.6), halides, germane, digermane,
silane, disilane, hydrazine and nitrogen trifluoride.
BACKGROUND
[0003] Highly reactive gases currently require storage at diluted
concentrations or storage at cryogenic temperatures to mitigate
decomposition, explosion, or deflagration. Dilution is the most
often preferred method of storage and can be achieved either by
using diluted gas mixtures, as is the case with 5% diborane stored
in bulk hydrogen, or by gas storage at low pressures, as in germane
or digermane. As a result of highly reactive gas dilution, the
volumetric loading of the highly reactive gas is limited.
SUMMARY
[0004] An embodiment is drawn to a method of adsorbing a highly
reactive gas onto an adsorbent material comprising adsorbing the
highly reactive gas to the adsorbent material. The absorbent
material comprises at least one Lewis basic functional group, or
pores of a size to hold a single molecule of the highly reactive
gas, or inert moieties which are provided to the adsorbent material
at the same time as the highly reactive gas, prior to adsorbing the
highly reactive gas or after adsorbing the highly reactive gas, or
the highly reactive gas reacts with moieties of the adsorbent
material resulting in passivation of the adsorbent material. A rate
of decomposition of the adsorbed highly reactive gas is lower than
a rate of decomposition for the neat gas at equal volumetric
loadings and equal temperatures for both the adsorbed highly
reactive gas and the neat gas.
[0005] Another embodiment is drawn to a method of adsorbing a
highly reactive gas onto a metal-organic framework (MOF) including
providing the highly reactive gas to the MOF, wherein the gas and
the MOF form a labile Lewis acid-base adduct which lowers a rate of
decomposition of the highly reactive gas relative to a rate of
decomposition of the neat highly reactive gas at the same
temperature and same volumetric loadings.
[0006] Another embodiment is drawn to a method of adsorbing a
highly reactive gas onto a metal-organic framework (MOF) comprising
providing the highly reactive gas to the MOF, wherein, the pores of
the MOF are sized to hold one molecule of the highly reactive
gas.
[0007] Another embodiment is drawn to a method of adsorbing a
highly reactive gas onto a metal-organic framework (MOF) comprising
reacting an initial dose of the highly reactive gas with the MOF,
wherein the initial dose of the highly reactive gas passivates the
MOF during the first adsorption cycle so that a rate of
decomposition of the adsorbed gas during subsequent adsorption
cycles is lower than a rate of decomposition of the adsorbed gas
during the first adsorption cycle and adsorbing an additional dose
of the highly reactive gas to the MOF subsequent to the initial
dose.
[0008] Another embodiment is drawn to a method of adsorbing a
highly reactive gas onto a metal-organic framework (MOF) comprising
reacting a fluid different from the highly reactive gas with the
adsorbent material, wherein the fluid passivates the adsorbent such
that a rate of decomposition of the reactive adsorbed gas is lower
than a rate of decomposition for the neat gas at equal volumetric
loadings and equal temperatures for both adsorbed gas and neat gas
and adsorbing the highly reactive gas to the MOF.
[0009] Another embodiment is drawn to a gas storage and dispensing
apparatus for a highly reactive gas comprising a container and an
adsorbent material located in the container. The absorbent material
comprises at least one Lewis basic functional group, inert moieties
which do not chemically react with the highly reactive gas, or
pores of a size to hold a single molecule of the highly reactive
gas, or moieties which react with the highly reactive gas resulting
in passivation of the adsorbent material.
[0010] Another embodiment is drawn to a method of adsorbing a
highly reactive gas onto an adsorbent material comprising adsorbing
a highly reactive gas to the adsorbent material and adsorbing inert
moieties to the absorbent material at the same time as the highly
reactive gas, prior to adsorbing the highly reactive gas or after
adsorbing the highly reactive gas. A rate of decomposition of the
adsorbed highly reactive gas is lower than a rate of decomposition
for the neat gas at equal volumetric loadings and equal temperature
for both the adsorbed highly reactive gas and neat gas.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a graph of the decomposition of diborane as a
function of diborane concentration.
[0012] FIG. 2 is a ball and stick model of the Van der Waals
geometry of diborane.
[0013] FIG. 3 is a graph illustrating the stability of fully
adsorbed diborane as a function of pore size.
[0014] FIG. 4 is a graph of the decomposition of adsorbed arsine
measured as a function of temperature.
[0015] FIGS. 5A-5B are ball and stick illustrations of some
metal-organic frameworks (MOFs) with preferred pore sizes for
stabilizing diborane, and FIG. 5C is a ball and stick illustration
of a MOF with Lewis base groups.
[0016] FIGS. 6A-6E are ball and stick illustrations of the
crystalline structures of other metal-organic frameworks
(MOFs).
[0017] FIG. 7 is a graph of sample cell pressure change over time
for a POP comprised of a polymerization product from styrene and a
cross-linking agent filled with B.sub.2H.sub.6.
DETAILED DESCRIPTION
[0018] Highly reactive gases can be defined as a category of gases
which spontaneously decompose upon shock, high pressure, or high
temperature. These gases can include: arsine (AsH.sub.3), stibine
(SbH.sub.3), phosphine (PH.sub.3), borane (BH.sub.3), diborane
(B.sub.2H.sub.6), halides, germane, digermane, silane, disilane,
hydrazine or nitrogen trifluoride. For example, diborane, widely
used as a dopant in semiconductor fabrication, is a highly reactive
molecule that readily decomposes and reacts at ambient temperature
to form higher order boranes, such as B.sub.5H.sub.9 and
B.sub.10H.sub.14, as well as hydrogen gas. As a result, neat
diborane is typically shipped and stored under significant
refrigeration (<-75.degree. C.) to slow the inherent thermal
decomposition. Another decomposition mitigation method includes
storing diborane by diluting it with hydrogen or nitrogen,
typically to 5% B.sub.2H.sub.6 or less by volume. The decomposition
of diborane increases as the concentration of diborane increases as
illustrated in FIG. 1, which is a plot of the estimated diborane
concentration versus time at various diborane concentrations. As a
result of the needed dilution to mitigate decomposition, storage
capacity is lost as is the ability to customize higher diborane
mixtures for end users.
[0019] In an embodiment, a highly reactive gas is adsorbed onto a
porous material. As a result of adsorption, the rate decomposition
of the highly reactive gas is lower than the rate of decomposition
of the neat highly reactive gas, at similar volumetric loadings and
similar temperatures. In effect, the adsorption of the highly
reactive gas acts to stabilize and mitigate inherent decomposition.
This effect is shown in the relative rate of the decomposition of
adsorbed arsine as illustrated in FIG. 4 as a function of an
estimated arsine pressure change versus time at various
temperatures. Arsine thermally decomposes into arsenic and hydrogen
according to Equation 1 below.
2 AsH 3 .DELTA. 2 As + 3 H 2 Equation 1 ##EQU00001##
[0020] The activation energy for the decomposition of arsine at a
bulk density of 5.5 mmol/mL and at 25.degree. C. is 150 kJ/mol and
134 kJ/mol for adsorbed arsine and neat arsine, respectively.
[0021] In preferred embodiments, the type of adsorbent used is a
metal-organic framework (MOF). MOFs are a class of sorbents, much
like zeolites or activated carbon. However, MOFs are composed of
metal nodes and organic linkers, as shown in FIGS. 5A-5C and 6A-6E.
In the various embodiments described herein, the MOFs of FIGS.
5A-5C and 6A-6E can be used or any other suitable MOFs can be used.
The combination of metal nodes and organic linkers provide a vast
array of near countless types of possible structures. For example,
the MOFs shown in FIGS. 5A-5C may be used to stabilize
B.sub.2H.sub.6 (or other reactive gases) while the MOFs shown in
FIGS. 6A, 6D and 6E may be used to stabilize other reactive gases.
In other embodiments, other adsorbents, such as activated (i.e.,
porous) carbon or porous organic polymers (POP) may be used.
[0022] In an embodiment, the adsorbent material comprises a porous
organic polymer (POP) comprising a polymerization product from at
least a plurality of organic monomers and comprising at least a
plurality of linked organic repeating units. In an alternative
embodiment, the adsorbent material comprises a porous carbon.
However, in preferred embodiments the adsorbent material comprises
a MOF.
[0023] In a first embodiment, a Lewis acid or Lewis base on gas
storage sites in the MOF is provided. In particular, the tunability
of the organic linker allows for the adsorption surfaces of the
MOFs or POPS or activated carbon to include various Lewis acidic
and/or Lewis basic functional groups. In an embodiment, the MOF,
POP or activated carbon includes one or more Lewis basic functional
groups and the highly reactive gas acts as a Lewis acid. In this
embodiment, the Lewis basic functional group in the MOF donates
electrons to the highly reactive gas, forming a dative bond and
thereby stabilizing the highly reactive gas. Lewis basic functional
groups may include, but are not limited to, any form or types of
amines, amides, imines, azo groups, azides, ethers, carbonyls,
alcohols, alkoxides, thiols, thiolates, isothiocyanates, sulfides,
sulfates, sulfites, sulfoxides, sulfones, disulfides, nitriles,
isonitriles, carboxylates, nitro groups, phosphates, phosphines,
phosphinates, borates, halides, aromatic groups (such as
heterocycles) alkynes, or alkenes. Exemplary heterocycles (i.e.
heterocyclic molecules) include 5 or 6 member rings having 1, 2 or
3 non-carbon atoms selected from one or more of P, Se, Sb, N, S,
Bi, O or As on the ring.
[0024] The addition of uniform, well placed Lewis acidic and/or
Lewis basic functional groups enables the stabilization of highly
reactive gases. Such is the case with diborane. When in the
presence of a Lewis base on the MOF, POP or activated carbon
storage site, diborane will homolytically cleave into two borane
molecules and form two Lewis acid-Lewis base pair that are more
stable than an uncleaved diborane molecule. This is observed in
borane adducts such as BH.sub.3.THF (tetrahydrofuran), a liquid
typically stored between 0-50.degree. C. to mitigate decomposition.
Analogously, borane adducts formed on the functionalized surfaces
of metal-organic frameworks lower the rate of decomposition of the
diborane precursor. Upon exposure to external stimuli, including
mild heat and/or vacuum, the borane adducts cleave, the borane
recombines to form diborane, and diborane is released or desorbed
from the sorbent. FIG. 5C illustrates an exemplary MOF
Zn.sub.4(O)(BDCNH.sub.2).sub.3, where BDC is benzene dicarboxylate,
which contains a Lewis base.
[0025] In another embodiment, the stabilization of adsorbed highly
reactive gases is accomplished through molecular segregation. In
this embodiment, the MOF, POP or activated carbon is engineered to
have at least some pores which hold a maximum of one molecule of
reactive gas. That is, at least some of the pores in the MOF, POP
or activated carbon have a pore size that is greater than the
diameter of the reactive gas molecule and less than twice the
diameter of the reactive gas molecule, such as between 1.1 and 1.5
times the diameter of the reactive gas molecule. Given the
crystalline nature of MOFs, pore sizes can be precisely tuned to
accommodate only one molecule of highly reactive gas.
Accommodation, for example, a single molecule of diborane results
in the stabilization of diborane. As mentioned above, diborane
thermally decomposes and reacts with other diborane molecules to
form higher order borane compounds and hydrogen gas (see equation 2
below and FIG. 1).
5 B 2 H 6 .DELTA. 2 B 5 H 9 + 6 H 2 Equation 2 ##EQU00002##
[0026] By segregating the diborane molecules, chemical collisions
are diminished and the rate of diborane decomposition is reduced.
Diborane has a van der Waals diameter of 3.6 .ANG., but the width
of diborane is approximated at 3.0 .ANG., as illustrated in FIG. 2.
As a result of the size of diborane, the stability of adsorbed
diborane is illustrated in FIG. 3 as a conceptual illustration as a
function of the pore size where the diborane fully fills the pore
of the adsorbent. As shown in FIG. 3, the stability of the highly
reactive diborane gas increases as the pore size increases. The
maximum stability is estimated to be at a pore size of
approximately 5 .ANG.. Once the pore size increases beyond 7.2
.ANG., the pore may accommodate multiple diborane molecules and
therefore the stability decreases. Thus, the preferred pore size
for diborane is 4-6 .ANG.. Examples of MOFs having a suitable pore
size include the following MOFs shown in FIGS. 5A, and 5B:
Mn.sub.3(BDC).sub.3 and Mg(pyrazole dicarboxylate).
[0027] In another embodiment, the stability of the adsorbed highly
reactive gas increases after the adsorbent material is passivated.
In an embodiment, this is achieved by treating the adsorbent
material with the highly reactive gas to modify sensitive moieties
in the adsorbent material to make the adsorbent less reactive to
the highly reactive gas. This method may comprise reacting an
initial dose of the highly reactive gas with the MOF, POP or
activated carbon to passivate the MOF, POP or activated carbon
during the first adsorption cycle followed by removing passivation
byproducts formed by reaction of the highly reactive gas with the
MOF, POP or activated carbon along with the sensitive moieties of
the MOF, POP or activated carbon. After removing the passivation
byproducts the method includes adsorbing additional highly reactive
gas to the MOF, POP or activated carbon subsequent to the initial
dose to store the gas in the MOF, POP or activated carbon. In an
embodiment, elevated temperatures (e.g. higher than room
temperature) and/or higher pressures (e.g. higher than 1 atm) can
be used to accelerate the passivation reactions.
[0028] Example sensitive moieties may include, but are not limited
to: 1) acidic moieties such as open-metal coordination sites,
carboxylic acid sites, or acidic cluster sites; 2) reducing agents
such as amines, incorporated metals, oxalic acid, formic acid, or
phosphites; and 3) oxidizing agents such as oxygenated clusters,
metal oxides, or peroxides. With the sensitive moieties passivated,
the highly reactive gas and other potential impurities are
desorbed. After subsequent highly reactive gas adsorption cycles,
the rate of decomposition is diminished given the passivation of
the sensitive adsorption moieties.
[0029] In an alternative embodiment, the passivation can be
achieved by using a different fluid, such as a strong oxidizer
(such as, but not limited to, oxygen, chlorine, fluorine, or
hydrogen peroxide) or reducing agent (such as, but not limited to,
hydrogen, ammonia, sulfur dioxide) rather than the reactive gas
used for storage. This method includes reacting the fluid (e.g. a
gas) different from the highly reactive gas with the adsorbent
material to passivate the adsorbent and then subsequently adsorbing
the highly reactive gas to the adsorbent material. Selection of the
desired concentration, pressure and temperature can be used to
modulate the reaction rates. Modulation of the reaction rates may
be used to achieve a desired passivation time or to prevent too
aggressive of a reaction that would undesirably degrade the MOF,
POP or activated carbon. The passivating fluid is preferably
selected based on its ability to produce reaction byproduct with
the sensitive moieties that can be removed easily. Once the MOF,
POP or activated carbon is passivated, the reactive fluid and any
reaction byproducts are removed from the vessel. In an embodiment,
removal of the byproducts may be aided by application of a vacuum
and/or application of heat. The vessel can be filled with the
highly reactive gas to adsorb it to the MOF, POP or activated
carbon after removal of the byproducts.
[0030] As an example, fluorine gas at a reduced concentration (5
vol %) may be introduced at a pressure of 1 atmosphere in the
vessel containing a MOF. Fluorine gas is a strong oxidizer that
reacts with reactive C--OH moieties present on the MOF surfaces to
produce gaseous HF and OF.sub.2 reaction products, resulting in the
replacement of the MOF C--OH sites with more stable C--F bonds.
[0031] In another embodiment, molecular segregation of a highly
reactive gas in an adsorbent material, such as a MOF, POP or
activated carbon, is accomplished by providing inert moieties into
the pores of the adsorbent material in addition to the reactive
gas. As used herein, an inert moiety is an atom or molecule which
does not chemically react with the highly reactive gas. As used
herein, "moieties" means plural atoms or molecules having the same
composition or different composition.
[0032] In one embodiment, the inert moieties are adsorbed in (e.g.,
onto) the pores by van der Waals forces. Preferably, the inert
moieties are not chemically bound to the adsorbent material.
[0033] The inert moieties are selected based on the reactivity of
the adsorbed highly reactive gas and the lack of chemical reaction
with the highly reactive gas. By way of example, examples of inert
moieties for diborane may include, but are not limited to hydrogen,
helium, nitrogen, aliphatic alkanes that comprise only of carbon
and hydrogen atoms, such as hexane, and aromatic rings that
comprise only of carbon and hydrogen atoms, such as benzene. In
addition to van der Waal forces, some inert moieties (e.g., inert
molecules) may fill the empty space due to capillary
condensation.
[0034] Without wishing to be bound by a particular theory, the
present inventors believe that the presence of inert moieties in
the pores of the adsorbent material diminishes the chemical
collisions between the highly reactive gas molecules (e.g., between
diborane molecules) and the rate of decomposition of the highly
reactive gas is reduced. In other words, it is believed that the
inert moieties (e.g., helium atoms) limits the movement of the
highly reactive gas molecules (e.g., diborane molecules).
[0035] Without wishing to be bound by a particular theory, the
present inventors believe that the presence of the inert moieties
increases the free energy of disassociation of the highly reactive
gas, which reduces the rate of decomposition of the highly reactive
gas. For example, biased Born-Oppenheimer molecular dynamic (BOND)
simulations with energies computed from density functional theory
(DFT) can be used to calculate the free energy necessary for the
dissociation of diborane into boranes (Equation 3) within the pores
of the adsorbent material:
B.sub.2H.sub.6.fwdarw.2BH.sub.3 Equation 3
[0036] This is believed to be the first step in the thermal
decomposition of diborane and that a higher free energy barrier
would result in a lower rate of decomposition. Introduction of
inert moieties, such as helium molecules, into an adsorbent
material, such as a MOF, is believed to increase the free energy
required to dissociate diborane by 10-20 kJ/mol relative to only
diborane adsorbed onto the same adsorbent material.
[0037] The highly reactive gas and the inert moieties may be added
to the adsorbent material in any order. In one embodiment, the
highly reactive gas is provided into the adsorbent material first,
for example to a maximum adsorption capacity of the adsorption
material for the highly reactive gas, followed by providing the
inert moieties into the adsorbent material. However, in other
embodiments, the highly reactive gas and the inert moieties are
provided into the adsorbent material at the same time, or the inert
moieties are provided into the adsorbent material prior to the
highly reactive gas.
[0038] In one embodiment, the pore size of at least some of the
pores of the adsorbent material is selected to fit only one
molecule of the highly reactive gas and one or more inert moieties
(e.g., one or more helium atoms), as described in a prior
embodiment.
[0039] In one or more of the above described embodiments, the
highly reactive gas stored (e.g., adsorbed) in an adsorbent
material contains at least one Lewis base, contains at least some
pores that are sized to fit only one highly reactive gas molecule,
is passivated and/or is filled with the inert moieties exhibits a
lower pressure change over time than neat highly reactive gas. For
example, the highly reactive gas stored (e.g., adsorbed) in an
adsorbent material exhibits at least 50% less, such as 50% to 200%
less pressure change (e.g., increase or decrease in pressure) over
8 days, than the same neat highly reactive gas at the same (i.e.,
equal) temperature (e.g., room temperature), the same (i.e., equal)
volumetric loading and the same (i.e., equal) initial pressure.
[0040] In one embodiment, the highly reactive gas stored (e.g.,
adsorbed) in the above described adsorbent material has a less than
25%, such as 0% to 25%, for example 5% to 20% pressure change from
an initial pressure over 8 days. In another embodiment, the highly
reactive gas stored (e.g., adsorbed) in the above described
adsorbent material does not exhibit an increase in pressure over at
least 8 days, such as 8 to 14 days, at room temperature.
[0041] In one non-limiting example, a stainless-steel sample cell
equipped with a pressure transducer and an isolation valve was
loaded with a POP comprising a polymerization product of styrene
and a divinyl benzene cross-linking agent. The POP is believed to
include at least some pores that are sized to fit only one diborane
molecule. Furthermore, the styrene POP precursor provides phenyl
groups that are believed to behave as an aromatic Lewis base. The
container was filled with B.sub.2H.sub.6 to 18.6 psia at ambient
temperature (22.degree. C.), resulting a volumetric loading of 1.4
mmol B.sub.2H.sub.6 per mL of POP. The sample cell was isolated
from the B.sub.2H.sub.6 source and the sample pressure was
monitored over time, as shown in FIG. 7. The effective pressure
change was determined to be 0.6 psia M.sup.-1 day.sup.-1 which was
lower than that of a neat B.sub.2H.sub.6 sample (1.6 psia M.sup.-1
day.sup.-1). The lower pressure change is believed to be evidence
of a lower decomposition of diborane stored in a POP containing a
Lewis base and at least some pores that are sized to fit only one
diborane molecule.
[0042] Although the foregoing refers to particular preferred
embodiments, it will be understood that the invention is not so
limited. It will occur to those of ordinary skill in the art that
various modifications may be made to the disclosed embodiments and
that such modifications are intended to be within the scope of the
invention. All of the publications, patent applications and patents
cited herein are incorporated herein by reference in their
entirety.
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