Patent Application
20240307849
Polymeric sorbent compositions are provided based on guanidine functionalized polymers of intrinsic microporosity.
Mitigation of CO2 emissions from various types of CO2 sources (both industrial and small-scale) is an area of ongoing interest. One type of strategy for mitigation of CO2 emissions is to use an adsorbent or absorbent to remove CO2 from a potential emission gas flow, and then desorb the CO2 as part of a stream that can be processed to reduce, minimize, or eliminate the release of CO2 into the atmosphere.
One difficulty with developing adsorbents for CO2 removal from gas streams is that many streams where CO2 removal would be desirable correspond to streams having relatively low concentrations of CO2. For example, exhaust streams from natural gas-fired plants for electric power generation typically contain roughly 4-5 vol % or less of CO2. Similar difficulties are present for direct air capture methods, where CO2 concentrations can be still lower. Thus, it would be desirable to have adsorbents that can effectively adsorb CO2 from such relatively dilute streams. Additionally, it would further be desirable if such adsorbents can also release the CO2 by exposing the adsorbent to desorption conditions that can be achieved with relatively modest expenditure of energy.
Polymers of intrinsic microporosity (PIMs) are porous organic polymers based on rigid and contorted macromolecular chains. The rigid and contorted macromolecular chains do not efficiently pack in the solid state, resulting in high porosity. Some examples of functionalized polymers of intrinsic microporosity are described in an article by Mason et al. titled “Polymers of Intrinsic Microporosity Incorporating Thioamide Functionality: Preparation and Gas Transport Properties” (Macromolecules, Vol. 44, pp. 6471 (2011)).
U.S. Pat. No. 8,715,397 describes a mixed amine and non-nucleophilic base CO2 scrubbing process for improved adsorption at increased temperatures.
U.S. Pat. No. 9,034,288 describes a CO2 scrubbing process including an alkanolamine CO2 sorbent in combination with a non-nucleophilic base.
A journal article by Jue et al. describes synthesis of PIM-1 (Macromolecules 2015, 48 (16), 5780-5790).
A journal article by Mason et al. describes synthesis of PIM-1, as well as synthesis of PIM-1-amine from PIM-1 (Macromolecules 2014, 47, 1021-1029).
A journal article by Alkhabbaz et al. describes impregnation of guanidylated polyallylamine into silica mesocellular foam (Fuel 2014 121 79-85).
In an aspect, a composition is provided corresponding to a polymer including repeat units having a backbone structure of a polymer of intrinsic microporosity, wherein at least a portion of the repeat units have a substituent attached to the backbone structure corresponding to a guanidine derivative and/or an amidine derivative, the guanidine derivative optionally being a guanidinyl functional group and/or the amidine derivative optionally being an amidinyl functional group.
In another aspect, a method is provided for sorbing CO2. The method includes exposing a polymer including repeat units having a backbone structure of a polymer of intrinsic microporosity to a gas phase environment containing CO2, wherein at least a portion of the repeat units have a substituent attached to the backbone structure corresponding to a guanidine derivative and/or an amidine derivative.
All numerical values within the detailed description and the claims herein are modified by “about” or “approximately” the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art.
In various aspects, functionalized polymer compositions are provided that can have beneficial properties for CO2 sorption and/or desorption. The functionalized polymer compositions can be based on polymers of intrinsic microporosity. The polymers of intrinsic microporosity can then be at least partially reacted to form polymers functionalized with guanidine derivatives and/or amidine derivatives, where at least a portion of the polymeric repeat units have a substituent that includes a guanidine derivative/amidine derivative as a functional group. Optionally, the guanidine-functionalized and/or amidine-functionalized polymers of intrinsic microporosity can be further reacted in order to further modify the guanidine derivative/amidine derivative that is substituted at one or more locations of a polymeric repeat unit. For example, guanidine derivative-substituted polymers of intrinsic microporosity can be formed. As another example, substituted polymers of intrinsic microporosity can be formed that include guanidine derivative substituents at only a portion of the locations that can potentially be functionalized. As still another example, amidine derivative-substituted polymers of intrinsic microporosity can be formed. As yet another example, substituted polymers of intrinsic microporosity can be formed that include amidine derivative substituents at only a portion of the locations that can potentially be functionalized. By varying the amount of guanidine derivative substitution and/or amidine derivative substitution present in the polymer, compositions with differing properties for CO2 sorption and/or desorption can be formed.
Polymers of Intrinsic Microporosity (PIMs) are an emerging material of interest for gas separations. Spiro centers integrated into the polymer backbone prevent efficient packing and induce permanent microporosity in the polymer. This permanent microporosity can be advantageously used through impregnation of CO2-philic molecules while still accommodating processability into a wide range of morphologies due to the solubility of the PIM in various common solvents.
In some aspects, it has been discovered that PIMs that include a nitrile group attached to the polymer backbone can be modified by replacing at least a portion of the nitrile functional groups with guanidine. For example, a first reaction can be used to convert substantially all of the nitrile groups to amines. At least a portion of the amines can then be converted to guanidine derivatives. In some aspects, the initial PIM can correspond to a PIM structure where the carbon of the nitrile group is bonded to an atom in a ring structure that forms part of the polymer backbone.
More generally, any convenient type of PIM that can be substituted to include a guanidine derivative without modifying the fused-ring backbone of the PIM can be used. Examples of PIM structures that can be modified to include guanidine derivatives are PIMs where a nitrogen-containing functional group is present in the PIM repeat unit and does not form part of the backbone structure (as defined below) of the PIM structural repeat units. Such functional groups can be susceptible to reaction using a variety of chemistries to convert a substituent location into a guanidine derivative. For example, the nitrile functional groups present in PIM-1 are attached to the backbone structure of a PIM-1 repeat unit via a bond between the carbon in the nitrile group and a carbon in a ring that forms part of the backbone structure. Such nitrile groups can, for example, first be converted into aminomethyl groups, and then converted into guanidine derivatives. As an example, it is noted that the nitrogen atom in the pyridine ring of the Py-PIM repeat unit is part of the backbone structure.
It has been discovered that functionalization of PIMs to include guanidine derivatives as substituents and/or amidine derivatives as substituents can reduce or minimize the surface area of the resulting functionalized PIMs. It has further been unexpectedly discovered that in spite of a reduction in the surface area of the resulting functionalized PIMs, substantial enhancements and/or modifications of CO2 sorption/desorption activity can be achieved relative to the PIMs prior to incorporation of guanidine derivatives/amidine derivatives as substituents.
In some aspects, a substantial portion (such as up to substantially all) of the potential substituent sites can be converted to guanidine derivatives and/or amidine derivatives. This can result in a polymer with improved CO2 adsorption properties. In other aspects, partial functionalization with guanidine derivatives and/or amidine derivatives can provide a structure having a mixture of functional groups with different levels of activity as either Lewis bases or Brønsted bases. The overall chemistry of CO2 sorption in these materials requires both types of basicity. By controlling the degree of functionalization with guanidine derivatives and/or amidine derivatives, these two base functions can be de-coupled. This affords the possibility of fine-tuning the CO2 sorption properties by varying the Lewis and Brønsted basicities independently. Since the nucleophilicity of the Lewis base directly affects the strength of the N—C bond that forms, it can be varied to alter the energy needed to break this bond to regenerate the free amine.
In such aspects, this can result in a polymer with improved CO2 sorption properties. Additionally or alternately, this can result in a polymer with improved properties for CO2 sorption from relatively dilute streams, such as CO2-containing streams having a CO2 concentration similar to the concentration found in exhaust streams from electric power plants that are fueled by combustion of natural gas.
Without being bound by any particular theory, it is believed that sorption behavior differences between guanidine- and amine-substituted PIM-1 samples represent differences in behavior based on the chemical nature of the heteroatomic functional substituent(s) present (amine, guanidine, or mixture thereof). Efficacy of the functional groups for CO2 sorption can depend on basicity, steric hindrance, electronic character, the presence or absence of water vapor, and whether additional heteroatomic functionalities are present.
A simple amine can interact with a CO2 molecule as either a nucleophilic Lewis base (electron donor) and/or a Brønsted base (proton acceptor).
If water is present, the ammonium carbamate product(s) can further react to form ammonium bicarbonate(s). Diammonium carbonates may also be present depending on factors such as mixture pH.
More complex nitrogenous functional groups, such as guanidines and amidines, can participate in this reaction sequence, with behavioral modifications consistent with structure. Guanidines have the general structure R—N(R′)—C(═NR″)—N(R′″)(R″″), wherein R is an organic substituent connected to the amidine through a C—N bond, and R′, R″, R′″, and R″″ are hydrogen or additional organic substituents and may be the same or different. Amidines have the general structure R—C(═NR″)—N(R′″)(R″″), wherein R is an organic substituent connected to the amidine through a C—N bond, and R″, R′″, and R″″ are hydrogen or additional organic substituents and may be the same or different. Guanidines and amidines are generally more Brønsted basic and less Lewis basic than simple amines although these properties are a function of R, R′, R″, R′″, and R″″. In a CO2 sorption system with a mixture of simple amines and guanidines (or amidines), it is presumed that the most prevalent carbamate reaction products will therefore be guanidinium (or amidinium) carbamates, where the more Lewis basic (nucleophilic) amine will comprise the anionic carbamate component of the product, and the more highly Brønsted basic, less nucleophilic guanidine (or amidine) will form the protonated component as shown in
For PIMs, strong driving force for CO2 chemisorption is created when functionalities with different reaction preferences are co-located along a polymer chain, such as a “mixed base” PIM bearing both simple amine and guanidine functionalities as shown in
In various aspects, such a guanidine-functionalized polymer and/or amidine-functionalized polymer can be used in a sorption/desorption process for removal of CO2 from a gas phase environment, such as a cyclic sorption/desorption process. In such aspects, after sorption of CO2 to form a sorption-enriched polymer comprising sorbed CO2, the CO2 sorbed to the sorption-enriched polymer can be at least partially removed to form a sorption-depleted polymer. In a cyclic process, such a sorption-depleted polymer can be ready for a subsequent cycle of sorption and desorption. Desorption can be achieved in any convenient manner. This can include modification of temperature (such as a temperature swing sorption/desorption cycle), modification of total pressure (such as a pressure swing sorption/desorption cycle), or a modification of CO2 partial pressure. It is noted that one option for modifying a CO2 partial pressure can be to modify the total pressure within an environment.
CO2-containing streams can be derived from a variety of sources. Some types of CO2 capture applications correspond to direct air capture (DAC), where air is the source of CO2. Direct air capture applications typically operate with an input CO2 concentration of roughly 0.04 vol %, although higher concentrations could be present if some type of preliminary CO2 enrichment is performed. Other sources of CO2 are exhaust or flue gases from various types of commercial power plants and/or production plants. Examples include exhaust gases from gas turbines (roughly 2.0 vol % to 4.0 vol % CO2), exhaust gases from coal-fired power plants (roughly 8.0 vol % to 15 vol % CO2), and exhaust gases from production of cement or steel, which can have CO2 concentrations of up to 20 vol %, or possibly still higher. Still other sources of CO2 can correspond to biogas streams formed during upgrading to bio-derived materials. Depending on the underlying process for forming the biogas, the CO2 content of biogas can range from 10 vol % to 50 vol %.
In this discussion, the backbone structure of a polymeric repeat unit is defined to include any atoms that can form part of a continuous path for connecting atoms at opposite ends of the repeat unit. When forming such a continuous path, each atom can be used only once in forming a given continuous path. However, it may be possible to draw multiple continuous paths that include a given atom. Thus, as an example, for a repeat unit that includes a cyclic (ring) structure with a methyl side chain, the methyl side chain cannot be part of a continuous path, as any effort to include the methyl side chain as part of the path would require passing twice through the atom in the ring structure where the methyl side chain is bonded.
In this discussion, at least a portion of a ring structure is defined as being part of the backbone structure when a continuous path for connecting the atoms at the ends of a polymeric repeat unit can be formed that passes through one or more atoms participating in a ring structure. In some aspects, a backbone structure can include a plurality of atoms from a single ring structure. In some aspects, a plurality of continuous paths may be available for connecting the atoms at the ends of a repeat unit. For example, for a cyclic structure that is integral to the backbone structure, it may be possible to form separate continuous paths that differ by at least one atom from the ring structure. In such aspects, the presence of separate continuous paths can allow all atoms in a single ring structure to be part of the backbone structure, even though no single continuous path includes all of the atoms from the ring structure. As an example, in the PIM-1 repeat unit, multiple continuous paths are available for connecting atoms at the ends of the repeat unit. Based on these multiple continuous paths, all atoms within each ring structure in the PIM-1 repeat unit are part of the backbone structure under the definition provided herein.
Based on the above definitions, it is noted that for a PIM-1 repeat unit, the atoms in the repeat unit that are not part of the backbone structure correspond to a) the two nitrile groups, and b) the methyl groups on the cyclopentyl ring. Similarly, for Py-PIM, the atoms in the repeat unit that are not part of the backbone structure are a) the single nitrile unit attached to the pyridine ring, and b) the methyl groups on the cyclopentyl ring.
In this discussion, guanidine derivative substituent is defined as any side chain attached to a PIM backbone structure that includes a) a central carbon atom that is bonded to b) three separate nitrogen atoms, with at least one of the bonds to a nitrogen atom having iminic (imine or double bond) and/or aromatic character. In some aspects, a guanidine derivative can correspond to a guanidinyl functional group, so that the only modification of the functional group relative to a guanidine molecule is the modification needed to bond the guanidinyl functional group to the PIM backbone structure and/or to a side chain attached to the PIM backbone structure. Optionally, the guanidine derivative in the side chain can be separated from the backbone structure by at least one aliphatic carbon, at least one aromatic carbon, or a combination thereof. As an example, the guanidinyl-substituted PIM-1 shown in
In this discussion, a guanidine-substituted PIM is defined as a PIM where at least a portion of the repeat units are modified to include a guanidine derivative substituent. Optionally, the guanidine derivative substituent can correspond to a guanidinyl group.
In this discussion, amidine derivative substituent is defined as any side chain attached to a PIM backbone structure that includes a) a central carbon atom that is bonded to b) two separate nitrogen atoms and one carbon atom, with at least one of the bonds to a nitrogen atom having iminic (imine or double bond) and/or aromatic character. In some aspects, an amidine derivative can correspond to a amidinyl functional group, so that the only modification of the functional group relative to an amidine molecule is the modification needed to bond the amidinyl functional group to the PIM backbone structure and/or to a side chain attached to the PIM backbone structure. Optionally, the amidine derivative in the side chain can be separated from the backbone structure by at least one aliphatic carbon, at least one aromatic carbon, or a combination thereof.
In this discussion, an amidine-substituted PIM is defined as a PIM where at least a portion of the repeat units are modified to include a amidine derivative substituent. Optionally, the amidine derivative substituent can correspond to a amidinyl group.
In this discussion, a functionalization location refers to a location in a PIM repeat unit where the repeat unit can be functionalized to include a guanidine derivative and/or amidine derivative. For example, for PIMs that include one or more nitrile groups in a repeat unit, the functionalization locations can correspond to the number of locations in a PIM repeat unit that correspond to nitrile groups. Thus, PIM-1 includes two functionalization locations per repeat unit, while Py-PIM includes only one nitrile per repeat unit. The amount of functionalization of a PIM with a guanidine derivative can be characterized based on the percentage of functionalization locations that are functionalized with a guanidine derivative versus the total number of functionalization locations. This percentage corresponds to a number average across a given PIM sample. It is noted that such functionalization with guanidine derivatives and/or amidine derivatives may not be evenly distributed throughout a polymer structure. Thus, a PIM 1 structure with 50% functionalization with guanidine derivatives may include some repeat units that include two guanidine derivatives while having other repeat units that include no guanidine derivatives. A PIM structure where less than 100% of the functionalization locations are functionalized with a guanidine derivative can be referred to as a partially functionalized PIM. In some aspects, a PIM can have 20% or more of functionalization locations that correspond to a guanidine derivative, or 40% or more, or 50% or more, or 60% or more, or 75% or more, such as up to substantially all of the functionalization locations corresponding to a guanidine derivative. In some aspects, a PIM can have 20% to 75% of the functionalization locations corresponding to guanidine derivatives, or 20% to 60%, or 20% to 50%, or 20% to 40%, or 40% to 75%, or 40% to 60%, or 50% to 75%, or 60% to 75%. It is also possible to attach multi-guanidine bearing derivatives at a functionalization location. For example, in some aspects, a PIM can be functionalized so that 70% or more of the repeat units (such as up to 100%) have a substituent corresponding to a guanidine derivative, or 30% to 70%, or 40% to 60%, or 10% to 30%.
Forming Polymers of Intrinsic Microporosity Functionalized with Guanidine Derivatives
The examples below describe various methods for addition of guanidine derivative functional groups as substituents to the polymer backbone for polymers of intrinsic microporosity.
After converting the nitrile substituents to aminomethyl substituents, the resulting functionalized PIM can be separated from the solvent environment. The PIM can then be exposed to conditions for conversion of at least a portion of the aminomethyl substituents to guanidines and/or guanidine derivatives. For example, the PIM can then be reacted with 1H-pyrazole-1-carboxamidine hydrochloride and diisopropylethylamine in dimethylformamide at 70° C. for a period of a few days, then rinsed with methanol and treated with sodium methoxide in methanol at room temperature, to convert at least a portion of the aminomethyl substituents into guanidines. Alternatively, the PIM can then be reacted with cyanamide in a water/ethanol solvent environment at a temperature between 50° C. to 100° C. for a time period between 1 hour and 100 hours to convert at least a portion of the aminomethyl substituents into guanidines.
The amount of amines that are converted to guanidine derivatives is dependent on the reaction specifics. When less guanidinylating reagent is added, at least a portion of the repeat units after the reaction can correspond to repeat unit 110 in
Other types of PIMs can be used to form functionalized PIMs.
More generally, it is noted that many types of PIMs are made by polymerization using a plurality of types of monomer units to form a PIM repeat unit. One type of reaction scheme to form PIMs is to use a first type of monomer containing catechol groups and a second type of monomer containing halogens to allow for formation of a repeat unit that includes a backbone structure corresponding to a PIM. PIMs where the repeat unit is based on a monomer that includes a nitrile group are examples of PIMs that can be functionalized to include a guanidine derivative. Examples of monomer units that contain a nitrile group that can be used to form a PIM repeat unit include 1,4-cyano-2,3,5,6-fluorobenzene and 4-cyano-2,3,5,6-fluorobenzene. It is noted that other halogens could be used in place of fluorine in the nitrile-containing monomer unit. Examples of PIMs where the repeat unit can be formed using a nitrile-containing monomer unit include, but are not limited to, PIM-1, PIM-4, PIM-CO-100, PIM-CO-15, and PIM-HP3.
Additionally or alternately, various types of additional functionalization strategies can be used to make functionalized PIMs with different types of functional groups and/or mixtures of functional groups.
PIM-1 was synthesized following the literature procedure with slight modifications (Macromolecules 2014, 47, 1021-1029.). All reagents not specified otherwise were reagent grade or better and used without further purification. Dimethylformamide (DMF) used in guanidinylation reactions was anhydrous grade. Tetrahydrofuran (THF) was dried/de-oxygenated. Other solvents used in chemical reactions were HPLC grade (dried over 3 Å molecular sieves). Solvents used for material washings were of ACS grade.
A 2.0 g (4.35 mmol repeat units) portion of the synthesized PIM-1 was dissolved in 70 mL dry THF in a round-bottomed flask under inert (N2) atmosphere. The solution was cooled down to 0° C. and neat BH3·SMe2 (20.0 mL, 212.48 mmol) was added dropwise while the reaction mixture was stirred vigorously. A yellow precipitate started forming during addition of BH3·SMe2. After stirring for 5 min in an ice bath, the reaction mixture was allowed to attain room temperature, and subsequently heated to reflux (80-85° C.) overnight. The reaction was quenched by dropwise addition of methanol (MeOH) at 0° C. The yellow precipitate was collected by filtration, and thoroughly washed with THF (×2 washes), followed by MeOH (×6 washes). The solid was suspended in 10% aqueous HCl and stirred for 4 h. During this period the color of the solid changed to pale orange. The solid was collected by filtration, washed thoroughly with doubly distilled water, followed by MeOH, and subsequently was stirred in 5% aqueous NaOH for ˜40 h at room temperature to neutralize the acid. The solid was collected by filtration, washed thoroughly with water until the pH of the filtrate became neutral, was further washed with MeOH, and finally dried under dynamic vacuum at 85° C. to obtain PIM-1-CH2NH2 (“PIM-1-amine”, 1.78 g).
Subsequently, a 1.0 g/2.14 mmol portion of PIM-1-amine (2.14 mmoles repeat units) was added to a round bottomed flask under N2 atmosphere along with 1H-pyrazole-1-carboxamidine hydrochloride (“PC·HCl”, 1.63 g, 11.1 mmol) and 35 mL of anhydrous DMF. The mixture was stirred for 5-7 min at room temperature to let 1H-pyrazole-1-carboxamidine hydrochloride completely dissolve in DMF. Dry diisopropylethylamine (DIPEA) (1.94 mL, 11.1 mmol) was then added to this suspension while stirring. The reaction vessel was then transferred to an oil bath heated at 70° C. and stirred under N2 atmosphere for 3 days. After 3 days the reaction mixture was allowed to attain room temperature followed by separating the solid crude out of the reaction solution by filtration. The solid was thoroughly washed with MeOH and air-dried. To another round bottomed flask charged with 1.2 g (22.2 mmol) NaOMe, 40 ml HPLC grade MeOH was added and subsequently stirred vigorously for 10 min. To this slightly turbid solution the air-dried guanidinylated polymer solid was added and stirred for 3-4 hours to neutralize the HCl complexed with the guanidine units. At this point, the product was isolated through filtration and thorough washing with MeOH. The product was finally dried in a vacuum oven under dynamic vacuum at 115° C. to obtain guanidinylated PIM-1 (1.09 g). This structure is referred to herein as PIM-1-guan or PIM-1-guan 100.
It is noted that thermogravimetric analysis was used to investigate the stability of the PIM-1, PIM-1-amine, and PIM-1-guan.
PIM-1 bearing both amine and guanidine groups was synthesized by adding a limited amount of the guanidinylating reagent (1H-pyrazole-1-carboxamidine hydrochloride, “PC·HCl”) with respect to the starting material (PIM-1-amine) to allow good control of the average ratio of primary amine to guanidine units. Three different round bottomed flasks were prepared, each containing 800 mg (1.71 mmol repeat units) of PIM-1-amine. To each of these was added between 0.9-3.0 mmol of PC·HCl followed by addition of a near equivalent molar amount of DIPEA. Subsequently, 30 ml anhydrous DMF was added to each of the flasks under N2 atmosphere. The reaction flasks were then transferred to an oil bath heated at 70° C. and stirring was continued for 3 days. After 3 days the reaction mixture was allowed to attain room temperature followed by separating the solid crude out of the reaction solution by filtration. The solids were thoroughly washed with MeOH and air-dried. Three fresh round bottomed flasks were each charged with 4 eq. of NaOMe per equivalent of PC·HCl along with 40 mL HPLC grade methanol. The contents of each flask were subsequently stirred vigorously for 10 min giving slightly turbid solutions. To these flasks the sample of the respective air-dried solid to be free based was added and the mixture was then stirred for 3-4 hours to neutralize the HCl complexed with the guanidine units. At this point, the polymeric products were isolated through filtration and thorough washing with MeOH. The products were finally dried in a vacuum oven under dynamic vacuum at 115° C. to obtain partially guanidinylated PIM-1-amines. These samples are shown in Table 1 below.
To summarize the three syntheses of partially guanidinylated PIM-1:
Solid-state quantitative 13C NMR (nuclear magnetic resonance) spectroscopy was performed to quantify the conversion and bulk purity of the product PIM-1-guanidines. The 13C NMR was conducted using a Bruker AV3-HD 300 MHz spectrometer (providing 75 MHz for 13C NMR). Qualitative measurements were taken using a 13C CP Magic Angle Spinning (MAS) sequence at 14 KHZ with a 4 mm MAS rotor (contact time 3 mS, ramp-shaped contact pulse for 1H, 4096 scans, 4 S recycle delay, 1024 complex data points recorded, spectral width 300 ppm). Quantitative measurements were taken on the same apparatus using a composite pulse MultiCP MAS sequence (contact time 100 mS, 512 scans, 5 S recycle delay, same number of data points and spectral width, and a proton repolarization time (d11) of 2×T1 (T1 was measured in a separate experiment using a saturation recovery sequence). Data was plotted using Bruker TopSpin 3.6.2 software.
Attenuated total reflectance (ATR) infrared (IR) spectra were also obtained to show absence of any residual starting material in the fully aminated and guanidinylated products. ATR-IR solid state spectroscopy was conducted using a Perkin-Elmer Spectrum Two FTIR spectrometer in ATR mode (diamond plate) at a resolution of 4 cm−1. A total of 32 scans were collected and data was analyzed using Spectrum Two SP-10 software, Automatic Performance Variation (APV). Spectra were plotted with Origin2021.
The complete conversion of PIM-1 to PIM-1-amine was confirmed from the disappearance of the C≡N stretching frequency at 2237 cm−1 in the ATR infrared spectrum of PIM-1-amine as shown in
Complete conversion of PIM-1-amine to its guanidinylated derivative is shown in overlaid ATR infrared spectra (
For the partially guanidinylated samples of Example 2, similar 13C-NMR spectra were obtained. The 13C-NMR spectra for the partially guanidinylated samples were then used to determine the relative amounts of primary amines and guanidinyl groups in the sample. The molar content of primary amines and guanidine units was calculated by comparing the signal integration value of the broad 13C SS NMR shoulder at 119 ppm (PIM-1-amine, adjacent to the signal at 113 ppm) with the newly appeared guanidine signal at ˜157 ppm as shown in
First, PIM-1-amine fibers were formed from PIM-1 fibers. To 200 mg (0.44 mmol repeat units) of PIM-1 fibers in a sealed round-bottomed flask was added 20 mL dry diethyl ether under inert (N2) atmosphere. Prior to reaction, the PIM-1 fibers had a bright yellow color (fluorescent under UV). The solution was cooled down to 0° C. and neat BH3·SMe2 (3.5 mL, 37.3 mmol) was added dropwise while the reaction mixture was stirred vigorously. After stirring for 15 min in an ice bath, the reaction mixture was allowed to attain room temperature while stirring, and subsequently heated to reflux (65-70° C.) for 24 h. At the end, the reaction was quenched by dropwise addition of MeOH at 0° C. The fibers turned to pale yellow at the end and were collected by filtration, and thoroughly washed with MeOH (×6). The solid was suspended in 10% HCl and stirred for 5 h, during which the color of the fibers changed to pale orange. After 5 hours the pale orange fibers were collected by filtration, washed thoroughly with doubly distilled water, followed by MeOH, and subsequently stirred in 5% aqueous NaOH for ˜40 h at room temperature to neutralize the acid. At this point the color of the fibers changed back to pale yellow; they were collected by filtration, and washed thoroughly with water until the pH of the filtrate became neutral. The fibers were further washed with MeOH, and finally dried under dynamic vacuum at 85° C. to obtain pale yellow amine-functionalized PIM fibers (199 mg) which are no longer fluorescent.
Next, the PIM-1-amine fibers were converted to fibers that included a guanidine derivative. To a round bottomed flask containing fibers of PIM-1-amine (190 mg, 0.41 mmol repeat units) was added 320 mg (2.20 mmol) of PC·HCl. Subsequently, 12 ml of anhydrous DMF was added to the flask under N2 atmosphere. The mixture was stirred for 10 min at room temperature to let the PC·HCl completely dissolve in DMF. Dry DIPEA (0.38 ml, 2.20 mmol) was then added to this mixture while stirring. The reaction vessel was transferred to an oil bath, heated at 70° C., and stirred under N2 atmosphere for 3 days. After 3 days the reaction mixture was allowed to attain room temperature followed by separating the pale brown fibers out of the reaction solution by filtration. The fibers were thoroughly washed with MeOH and air-dried. Subsequently, to another round bottomed flask charged with 475.3 mg (8.8 mmol) NaOMe, 25 ml HPLC grade MeOH was added and subsequently stirred vigorously for 15 min. To this slightly turbid solution, the air-dried fibers were then added, and stirred for 4-5 hours to neutralize the HCl complexed with the guanidine units. At this point, the neutralized fibers were isolated through filtration and thorough washing with MeOH. The fibers were finally dried in a vacuum oven under dynamic vacuum at 115° C. to obtain light brown guanidinylated PIM-1 fibers (210 mg).
Table 1 summarizes all of the guanidinylated PIM-1 samples and precursors.
CO2 sorption isotherms were taken on a Micromeritics ASAP 2020 instrument running MicroActive software. The degas (evacuation) cycle was conducted at 150° C. for 720 minutes (hold pressure 100 mm Hg) with a ramp rate to this temperature of 10° C./minute. Isothermal analysis was conducted at 30° C. for 720 minutes under CO2 at gradually increasing pressures up to 1 bar. Data was plotted with Origin2021.
CO2 sorption isobars were taken using a TA Instruments Q500 QSeries Thermogravimetric Analyzer (TGA). Data was analyzed using TA Universal Analysis software. Starting at room temperature, the sample was heated to 150° C. at a ramp rate of 20° C./minute under an air flow of 90 mL/minute. It was held at 150° C. for 80 minutes as a pre-drying step under a nitrogen flow of 90 mL/minute. The adsorption portion of the isobar was taken by cooling to 30° C. at a rate of 0.5° C./minute under a CO2 flow of 25 mL/minute. The desorption portion was taken by heating to 150° C. under identical conditions.
Sorption kinetics experiments were performed using an identical instrument. The sample was first heated at 150° C. under nitrogen for 80 minutes, then cooled to 30° C. under dry nitrogen flowing at a rate of 90 mL/minute. CO2 sorption was conducted at 30° C. for 6 hours under a dry CO2 flow of 25 mL/minute, followed by desorption (under the same gas flow) by heating to 150° C. at a rate of 0.5° C./minute.
Humid sorption kinetics experiments were performed using a TA TGA500 instrument. The sample was first heated at 150° C. under nitrogen for 60 minutes, then cooled to 30° C. under dry nitrogen flowing at a rate of 90 mL/minute. The sample was then saturated with moisture through the flow of humid N2 (at 50% RH, 30° C.) for 2 hours. CO2 sorption was then conducted at 30° C. for 2 hours under a moist CO2 flow of 25 mL/minute, followed by desorption (under dry N2) by heating to 150° C. at a rate of 0.2° C./minute. The humid adsorption steps were performed by flowing the gases through a LI-COR humidifier (portable dew point generator, Model LI-610) and then through the sample.
Sample decomposition profiles were taken using an identical instrument. Starting at room temperature, the sample was heated at a rate of 15° C./minute to 800° C. in air with a 90 mL/minute flow. It was then held at 800° C. for 30 minutes under the same air flow, and cooled to 30° C. at a rate of 20° C./minute under the same air flow.
In
Material PIM-1-guan100 was further compared to its di-HCl salt, PIM-1-guan 100·HCl, based on dry isobaric CO2 sorption at 100 kPa and breakthrough at 35° C. with 4.5% CO2 in He. PIM-1-guan100·HCl corresponds to an acid neutralized version of PIM-1-guan 100. PIM-1-guan 100·HCl has its strong Brønsted base sites deactivated by formation of guanidinium hydrochlorides, unlike the free guanidinyl base in PIM-1-guan100. As a result, PIM-1-guan 100·HCl is not expected to show strong interactions with CO2. As demonstrated in
In some aspects, the benefits of having water present in a gas where CO2 is being sorbed can be achieved for relative humidity values of 5.0% or higher, or 15% or higher, such as up to 100% relative humidity. In some aspects, the relative humidity can be 5.0% to 95%, or 5.0% to 50%, or 50% to 95%.
In some aspects, the CO2 concentration in a gas where CO2 is being sorbed can be 30 vol % or less, or 20 vol % or less, or 10 vol % or less. For example, the CO2 concentration can be 0.02 vol % (i.e, 200 vppm) to 30 vol %, or 0.02 vol % to 20 vol %, or 0.02 vol % to 10 vol %, or 0.02 vol % to 6.0 vol %, or 1.0 vol % to 30 vol %, or 1.0 vol % to 20 vol % or 1.0 vol % to 10 vol %, or 1.0 vol % to 6.0 vol %, or 5.0 vol % to 30 vol %, or 5.0 vol % to 20 vol %, or 8.0 vol % to 30 vol %.
While the present invention has been described and illustrated by reference to particular embodiments, those of ordinary skill in the art will appreciate that the invention lends itself to variations not necessarily illustrated herein. For this reason, then, reference should be made solely to the appended claims for purposes of determining the true scope of the present invention.
