of 7
Accelerated screening of carbon dioxide capture by
liquid sorbents
Ryan J. R. Jones,
a
Yungchieh Lai,
a
Kevin Kan,
a
Dan Guevarra,
a
Joel A. Haber,
a
Natalia M. Ramirez,
b
Alessandra Zito,
b
Clarabella Li,
b
Jenny Y. Yang,
b
Aaron M. Appel
c
and John M. Gregoire
*
a
The ideation of carbon capture, concentration, and utilization technologies is establishing a need for carbon
dioxide sorbents with speci
fi
c binding, release, and chemical speci
fi
cations. While computational work
fl
ows
can help navigate the broad search space of molecular sorbents, automated experimental screening
platforms are relatively underdeveloped. We present a carbon capture screening instrument to characterize
the carbon dioxide binding and sorption capacity of liquid sorbent media. We discuss the extension of this
capability to characterize the loaded liquid sorbent as well as the headspace to facilitate study of the
carbon dioxide adduct, for example its electrochemical activation. The fabrication and computer
automation instructions are provided so that the experimental technique can be implemented in a broad
range of materials acceleration platforms involving gas sorption.
Introduction
The e
ffi
cient sorption of CO
2
from dilute gas streams is a crit-
ical process for enabling carbon sequestration and sustainable
energy technologies.
1,2
McDannald
et al.
3
presented the value
proposition for developing a mat
erials acceleration platform
(MAP)
4
for discovery of CO
2
sorbents, and recent advance-
ments in computational predictions
5
highlight the need for an
automated experimental screening instrument. Thermogravi-
metric analysis (TGA)
6
is a traditional method for measure-
ment of CO
2
sorption, where the weight-change of a sorbent in
aCO
2
-containing atmosphere is assumed to be due to CO
2
sorption a
er calibrating and accounting for solvent evapo-
ration. TGA is particularly convenient for studying sorbents for
thermal CO
2
release, as the temperature-dependence of CO
2
binding is readily measured
via
temperature control in the
system. For sorbents that are int
ended to be electrochemically
regenerated
7
and/or used in reactive capture and conversion
(RCC) schemes
via
electrochemical reduction to carbon-
containing chemicals or fuels,
8
it is desirable to couple the
sorption experiment with an electrochemical cell. While
awettedwallcolumn
9
system may be adapted for such
purposes, the engineering in such systems is focused on
quantitative control of the liquid
gas interface to monitor
sorption kinetics, requiring re
latively large liquid sorbent
volumes and posing challenges for rapid system cleaning. We
present herein the carbon capture screening instrument
(CCSI), which characterizes CO
2
sorption
via
an infrared
measurement of the partial pressure of gas-phase CO
2
.While
detailed infrared spectroscopy measurements can be used to
observe the speciation of sorbed CO
2
as well as molecular
CO
2
,
10
the CCSI employs a relatively inexpensive sensor from
Gas Sensing Solutions. The CCSI instrument also interfaces to
automated preparation of liquid sorbent media. The target use
is for screening of molecular sorbents. While robotic coupling
to molecular synthesis instru
ments may be developed in the
future, the present work discusses the mixture of sorbent-
loaded solvent with co-solven
ts or additives, which have
been shown to considerably mod
ify the sorption behavior.
11
A
er the custom preparation of the sorbent media and char-
acterization of its CO
2
sorption characteri
stics, the CCSI is
design to enabled automated transfer of both the liquid and
gas phases to instrumentation for further analysis. For RCC
experiments, this liquid anal
ysisisintendedtobeelectro-
chemical characterization, although that capability is not
demonstrated in the present work. Herein we introduce the
CCSI design, demonstrate its operation with hydroxide solu-
tions, and present an initial screening experiment for a phen-
oxide sorbent. The ESI
includes pseudo-code for operation,
Python code for incorporation into the HELAO-async
12
instrument control platform, a fabrication guide, machining
instructions for custom parts, computer drawings, and a parts
list with estimated pricing.
a
Division of Engineering and Applied Science, California Institute of Technology,
Pasadena, CA 91125, USA. E-mail: gregoire@caltech.edu
b
Department of Chemistry, University of California, Irvine, California 92697, USA
c
Institute for Integrated Catalysis, Paci
c Northwest National Laboratory, Richland,
Washington 99352, USA
Electronic supplementary information (ESI) available: Molecular sorbent
synthesis data, CCSI assembly instructions, CCSI automation using helao-async,
and CCSI bill of materials. See DOI:
https://doi.org/10.1039/d3dd00232b
Cite this:
Digital Discovery
,2024,
3
,
674
Received 3rd December 2023
Accepted 23rd February 2024
DOI: 10.1039/d3dd00232b
rsc.li/digitaldiscovery
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Results and discussion
The carbon capture screening instrument
The CCSI instrument is shown in Fig. 1a with the liquid and gas
handling diagram shown in Fig. 1b. The system is designed to
measure the partial pressure of CO
2
in the headspace (
p
CO
2
)
using an infrared sensor while the headspace is bubbled
through the liquid sorbent media
via
the recirculation pump,
which accelerates gas
liquid equilibration. Starting from
a given amount of CO
2
in the headspace, the CCSI can be
operated in a
constant moles
mode in which the sensor
measures the rate of sorption of CO
2
from the headspace. A
thermodynamic assessment of the CO
2
sorption in this oper-
ating mode relies on precise measurement of
p
CO
2
, especially at
low partial pressures. Alternatively, CCSI can be operated in
a
constant pressure
mode by implementing a feedback loop to
inject CO
2
into the headspace to maintain a constant
p
CO
2
. This
mode of operation is preferred for characterizing sorption
thermodynamics, as discussed further below. We also note our
anecdotal observation that reliable measurement of the low
p
CO
2
values encountered in
constant moles
mode required
frequent sensor calibration, which is undesirable for deploy-
ment of CCSI for accelerated sorbent screening. While CCSI
may accommodate experiments at various total pressures, the
present work is limited to near-ambient (1 atm) headspace
pressure. A total pressure gauge in included in the system,
although the data from this sensor is not used in the present
work.
The high-level steps of the CCSI instrument for each exper-
iment cycle are shown in Fig. 1c, and the pseudo-code showing
the granular execution of these steps is provided in the ESI.
The liquid sorbent for each CCSI experiment is automatically
prepared
via
programmed injection into the sorption chamber
from 1 or more syringe pumps. The headspace is prepared prior
to the injection of the liquid sorbent, and the sorption experi-
ment is considered to start at the initiation of the sorbent
injection into the recirculation cell. A
er liquid injection, the
recirculation pump is activated for the duration of the
measurement, which is 1 hour for most measurements in the
present work. We note that within a couple minutes, the data
exhibits whether there is substantial CO
2
sorption from the
given headspace, although for the present work we conduct
longer experiments to observe the path toward gas
liquid
equilibration. As noted in Fig. 1c, the experiment cycle
concludes by extraction of the liquid and purging of the
instrument.
The headspace for each CCSI experiment is prepared in one
of 2 ways. A gas cylinder with 9.85
±
0.2% CO
2
in N
2
from Airgas
provides the standard process gas. Flushing the system with
this gas, injecting the liquid sorbent, and sealing the system
provides the initial state where the moles of CO
2
in the system is
limited to the headspace volume at 0.099 atm CO
2
. The amount
of CO
2
sorbed by the liquid (
m
tot
) is then determined by the CO
2
added to the system
via
the mass
ow controller (MFC) to
maintain this
p
CO
2
.
Fig. 1
The Carbon Capture Screening Instrument (CCSI). (a) The computer drawing of the primary components shows the valve and pump
layout for automating headspace and liquid sorbent preparation, execution of the sorption experiment under constant partial pressure of CO
2
,
and post-sorption characterization of the sorbent and/or headspace. (b) The CCSI schematic further outlines the gas and liquid handling system
including
Syringe pump A
, which houses the primary sorbent media, and the sorbent media preparation may be expanded using additional
syringe pumps accommodated by the
fl
ow selection valve. The base solvent, which is deionized water in the present work, is heavily used during
cleaning procedures, motivating its integration with a reservoir for automated syringe re
fi
ll. The analogous gas used for system
fl
ushing and
headspace initialization is either N
2
or a chosen CO
2
gas mixture. Additionally, CO
2
and N
2
gases provided by mass
fl
ow controllers (MFCs) enable
controlled dosing of the headspace. The MFCs have integrated solenoid valves, with the CO
2
valve in an upstream con
fi
guration because this
MFC has an integrated total pressure sensor for auxiliary monitoring of the system. The primary recirculation loop for sorption measurements is
highlighted in red. The valving con
fi
guration for optional additions to the system are shown, including a recirculation loop for sorbent analysis
and a
fl
ow-through knockout drum for headspace analysis. (c) The high-level states for CCSI operation are shown where the optional post-
sorption analyses are marked (
*
). After initialization, automated execution of the sample loop can be used to characterize various sorbent
formulations, gas compositions, and or post-sorption analyses.
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If there are multiple values of
p
CO
2
that will be routinely used,
custom gases may be prepared accordingly and selected as the
source gas for this primary method of preparing the headspace.
In our standard operation, we occasionally use lower pressures
of CO
2
,
e.g.
1% or 0.1%, which we prepare
via
an alternative
method wherein the atmosphere is initialized with pure N
2
.
A
er liquid injection and sealing of the system, the feedback
loop for maintaining the setpoint
p
CO
2
is started, where low CO
2
in the headspace results in immediate CO
2
injection. From
here, the experiment proceeds as described above, and the
calculation of
m
tot
accounts for the CO
2
from the MFC that is in
the gas phase.
While
m
tot
quanti
es the amount of CO
2
in the liquid phase,
the goal of the CCSI experiment is to quantify the chemically
bound CO
2
. Thus,
m
tot
is modelled as the sum of the phys-
isorbed unbound CO
2
(
m
phys
), as dictated by Henry's Law coef-
cient for the solvent, and the chemisorbed CO
2
(
m
chem
).
Demonstration with hydroxide sorbent
To demonstrate the operation of CCSI, two syringe pumps were
loaded with deionized water and aqueous 0.2 M KOH solution.
The programmed mixing of solutions from these syringe pumps
enabled characterization of sorption from aqueous solutions
containing 0.02, 0.05, and 0.1 M KOH.
Fig. 2 shows example data for select combinations of [KOH]
and
p
CO
2
where the CO
2
sorption is evidenced by an initial
decrease in the
p
CO
2
signal, which triggers periodic injection of
CO
2
to eventually restore the headspace to its initial value of
p
CO
2
. For the aqueous KOH experiments,
m
phys
is calculated as
the product of the Henry's coe
ffi
cient for CO
2
in water (0.033 M
atm
1
) and the
p
CO
2
for the respective experiment. The reaction
of CO
2
and OH
can result in either carbonate or bicarbonate,
whose relative concentration may be determined by measuring
the pH of the liquid, where carbonate is the dominant species
above pH
10 and bicarbonate is the dominant species below
pH
10. Fig. 3 shows the value of
m
chem
with respect to the
Fig. 2
Sorption data from the CO
2
sensor (left axes) and the MFC (right axes) for 4 experiments with the noted combinations of aqueous [KOH]
and headspace composition. After setting the partial pressure setpoint at the beginning of each experiment, CO
2
sorption by the liquid sorbent
triggers injection of pure CO
2
in the headspace, as indicated by the spikes in the MFC
fl
ow rate. The stabilization of the partial pressure signal and
concomitant lowering of the CO
2
injection frequency indicate that the headspace and liquid sorbent are approaching equilibrium.
Fig. 3
The data from the four 1 hour experiments in Fig. 2 are
summarized to show the relationship between the inferred amount of
chemisorbed CO
2
and the amount of OH
in the initial liquid sorbent.
The experiment with lowest [KOH] and partial pressure was extended
to 5 hours, where the measured pH of the liquid sorbent (pH 12.2)
corroborates the approximately 1 : 2 ratio of the chemisorbed CO
2
and
hydroxide expected for formation of carbonate as the primary dis-
solved inorganic carbon species. For the other 3 experiments, this ratio
is approximately 1 : 1, corresponding to the formation of bicarbonate.
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loading of KOH for each of the 4 experiments. For 3 of these
experiments, the pH was measured a
er the CCSI experiment.
The measurements with 9.9% CO
2
in the headspace follow the
expected trend for reaction of OH
and CO
2
to form KHCO
3
,
which is corroborated by the measurement of near-neutral pH
for each liquid. The measurement with 0.1% CO
2
more closely
matches the expected value of
m
chem
for the formation of
K
2
CO
3
. Due the anticipated poor kinetics for equilibration due
to the low
p
CO
2
and low initial [KOH], this measurement was
extended to 5 hours, a
er which the measured pH of 12.15
corroborates the formation of carbonate as the primary species
of dissolved inorganic carbon.
Screening a molecular sorbent
The primary purpose of the CCSI measurement is to charac-
terize the chemisorption of CO
2
of a sorbent molecule R dis-
solved into a liquid solvent. If the chemisorbed state of the CO
2
is RCO
2
, the equilibrium of RCO
2
with the sorbent R under
aCO
2
partial pressure
p
CO
2
is described by the binding constant
K
¼
½
RCO
2

½
R

p
CO
2
;
(1)
where
p
CO
2
is a fraction with respect to the standard condition of
1 atm such that
K
is unitless.
13
Starting with a molar loading of
sorbent
m
0
, the CO
2
sorbed during the CCSI experiment (
m
tot
)is
adjusted by
m
phys
, which is assumed to be independent of the
identity and concentration of R. The resulting amount of
chemisorbed CO
2
(
m
chem
) is taken to be the amount of RCO
2
.
Under these assumptions, the quasi-equilibrium state observed
at the end of a CCSI sorption experiment can be described by
the apparent binding constant
K
app
calculated from eqn (1):
K
app
¼
m
chem
ð
m
0

m
chem
Þ
p
CO
2
:
(2)
The error and uncertainty of this quantity will be minimized
when the concentrations of R and RCO
2
are approximately
equal, which for a given expected binding constant
K
motivates
the choice of
p
CO
2
z
1
K
:
However, for a binding constant larger than 10
3
,whichis
required for capture from dilute sources of CO
2
,thepoortransfer
kinetics at the corresponding low
p
CO
2
may lead to undesirably
long experiment times to equilibrate the liquid sorbent and
headspace. For primary screening, we propose using a
ca.
10% CO
2
atmosphere, which is su
ffi
cient to identify the sorbents with
binding constants between approximately 10
1
and 10
2
.If
m
RCO
2
is
found to be approximately equal to
m
0
, then the apparent binding
constant is too large to be adequately characterized with
p
CO
2
=
9.9%, motivating additional experiments with lower values, such
as the 0.1% CO
2
atmospheres used in Fig. 2.
Tetramethylammonium penta
uorophenoxide is a novel
molecular sorbent, whose synthesis is characterized by nuclear
magnetic resonance (NMR) and Fourier transform infrared
spectroscopy (FTIR) in Fig. S1
S5.
Fig. 4 shows the CCSI data
for 9.9% CO
2
headspace with aqueous 0.1 M tetramethy-
lammonium penta
uorophenoxide sorbent, corresponding to
m
0
=
0.5 mmol in the 5 mL aqueous solvent. The
p
CO
2
and CO
2
injection data are shown in Fig. 4, whose analysis provides
m
tot
=
0.07 (mmol) a
er the
1 h experiment, with
m
phys
=
0.0165
(mmol) from the presumed free CO
2
physisorbed in the
aqueous solvent. We note that
m
tot
reached 80% and 90% of this
value a
er
ca.
550 and 750 s, respectively, highlighting the
opportunity to accelerate sorbent screening as needed.
Following the analysis of eqn (2), the
m
chem
=
0.0542 mmol
corresponds to an apparent binding constant
K
app
=
1.35. While
this value is insu
ffi
cient for applications such as direct air
capture, the rapid acquisition of this value from an automated
system demonstrates the ability of the CCSI instrument to
accelerate sorbent discovery e
ff
orts.
Safety and build validation
Provided adherence to standard safety practices regarding
compressed gasses, the chemical components of the sorbent
media, and the control electronics, we do not envision any safety
hazards that emerge from the CCSI design. While the CCSI in
intended to operate at total pressures near 5 psi above ambient,
the use of pressure-relieving regulators can help mitigate exposure
of the user and equipment to unsafe pressures. Given the intended
use as a screening tool for novel chemical sorbents, the primary
safety evaluation for implementation of the CCSI in research
work
ows involves any chemical hazards of the sorbent media. For
example, the KOH-based sorbent media demonstrated herein
requires adherence to handling of caustic media.
While component-level operation instructions are provided
in the ESI,
we recommend the following evaluations to validate
the CCSI assembly. The
rst validation is against atmospheric
leaks, which can be performed by purging the system with N
2
gas until the CO
2
sensor reaches its noise
oor, following by
sealing the headspace and recirculating the gas using the
recirculation pump. The CO
2
sensor time series should then
characterize the leak rate of CO
2
in the system, which should be
below 10 ppm s
1
, although the acceptable rate depends on the
intended system use with respect to sorption strength,
p
CO
2
, and
measurement duration. The analogous experiment can be per-
formed with the standard gas intended for sorbent screening,
i.e.
9.9% CO
2
in the present work, where any decline in the
measured
p
CO
2
during sealed headspace recirculation indicates
a leak to atmosphere. In both cases, we note that the di
ff
usion
of gasses through plastic tubing may provide an apparent
nonzero leak rate. With the gas handling validated, we recom-
mend that the
rst set of sorption experiments involve a known
strong sorbent. For example, reproduction of Fig. 3 by per-
forming the experiments shown in Fig. 2 should provide su
ffi
-
cient quantitative characterization of the CCSI to enable
subsequent characterization of novel sorbents.
Adaptions and additional considerations
We note that for all experiments in the present work,
p
CO
2
was
determined by using the premixed 9.9% CO
2
gas or by dosing
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a pure N
2
to obtain 0.1% CO
2
. In the former preparation, the
reading from the CO
2
sensor is recorded a
er the headspace is
prepared, providing the setpoint value for the feedback control
of the CO
2
injections. With this method, the absolute accuracy
of the CO
2
sensor is inconsequential. We anecdotally observed
that the absolute reading can dri
. For automated execution of
lower
p
CO
2
experiments,
e.g.
0.1%, the zero-level of the sensor
should be calibrated in the pure N
2
atmosphere to ensure
accurate preparation of the gas
via
MFC feedback to the setpoint
p
CO
2
.
The MFC control algorithm used in the present work is
relatively simple and designed to mitigate the over-
pressurization of CO
2
in the system. We believe that the gas
liquid exchange kinetics are the limiting factor for experiment
throughput, although we note the opportunity for increasing
the e
ffi
ciency of
p
CO
2
through, for example, a proportional
integral
derivative (PID) controller.
The CCSI system provides the ability for post-sorption
analysis of the sorbent media. In the present work, this anal-
ysis is limited to manual pH measurements. Fig. 1b illustrates
the valve con
guration for implementing post-sorption char-
acterization of the CO
2
-loaded liquid and headspace gas. These
steps are noted as optional in Fig. 1c, and the pseudo-code
provided in the ESI
includes the steps for executing such
post-sorption analyses, as well as the additional cleaning steps.
To the best of our knowledge, there is no commercial
analogue to the CCSI instrument, with automated preparation
of sorbent media, execution of sorption characterization, and
triggering subsequent liquid and gas analyses. The design
employed herein o
ff
ers a relatively inexpensive set of compo-
nents, as detailed in the ESI.
Compared to a TGA instrument,
which can cost upwards of 10 000 U.S.D., the CCSI components
are comparable and possibly lower depending on factors such
as availability of an existing computer, the chemical compati-
bility of components (the present build can handle aqueous and
nonaqueous solvents, while several valve and tubing compo-
nents may be replaced with less expensive alternatives for
aqueous-only operation), and the sorbent media preparation
manifold. The biggest variable in the system cost is the choice of
recirculation pump, which can be
ca.
1000 U.S.D. for an inex-
pensive peristaltic pump using tubing with limited chemical
compatibility, to
ca.
4000 U.S.D. for a diaphragm pump with
PEEK tubing, which increases chemical compatibility and
enables pumping of viscous sorbent media. We note that in the
present work the recirculation pump acts only on the head-
space, but we envision pumping on the liquid sorbent in
subsequent electrochemical characterization using a recircula-
tion cell design that we previously reported.
14
We have built
multiple versions of the CCSI with di
ff
erent choices of pumps to
meet di
ff
erent speci
cations of the sorbent media. To our
knowledge, no similar instrument has been replicated in an
independent laboratory.
Experimental
The parts list and assembly instructions are provided in the
ESI.
The tubing used for the primary data include primarily
polyether ether ketone tubing with a short segment of Viton
tubing used in the 300 rpm Master
ex C/L 77122-24 peristaltic
pump for recirculation. To avoid the use of the so
-walled
tubing and to expand the chemical compatibility of the
system, the pump can be replaced with, for example, a KNF
SIMDOS 02 diaphragm pump. The CO
2
sensor is a Gas Sensing
Solutions SprintIR6S-20. Reported pH measurements were
acquired with an OAKTON PC700 pH meter. Additional custom
machined parts are described in the ESI.
The 18.2 M
U
water used to prepare all sorbent media was
from a Millipore Milli-Q Advantage A10. The KOH solution was
prepared
via
dissolution of KOH pellets (Macron Fine Chem-
icals, AR-ACS). The two pure gases are 99.999%, 99.998% for
CO
2
and N
2
, respectively, and the gas mixture is 9.85
±
0.2%
CO
2
in N
2
(airgas).
Synthetic work was carried out in ambient air and environ-
ment. All solvents and reagents were purchased from
commercial vendors and used without further puri
cation
unless otherwise noted. Deuterated DMSO used for NMR
characterization was purchased from Cambridge Isotope
Laboratories, Inc., as was degassed
via
the free
pump
thaw
Fig. 4
The CCSI data for the sorption of CO
2
from a 9.9% atmosphere by an aqueous 0.1 M tetramethylammonium penta
fl
uorophenoxide
sorbent. The headspace was initialized using a pre-prepared gas with 9.9% CO
2
, which is taken to be the true partial pressure in the headspace.
The sensor reports approximately 11% partial pressure, but since this value is only used as the setpoint for maintaining constant partial pressure,
the numerical evaluation of CO
2
sorption is provided by the amount of CO
2
from the MFC injection into the headspace, which concludes after an
apparent equilibrium is reach after 25 minutes of gas recirculation through the liquid sorbent.
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method and stored over activated 3 Å molecular sieves in
a glovebox.
Fourier Transform Infrared (FTIR) spectroscopy was per-
formed using a Thermo Scienti
c Nicolet iS5 FTIR Spectrometer
with iD5 diamond ATR.
1
H,
13
C{
1
H}, and
19
F{
1
H} NMR and
spectra were recorded on a 600 MHz Varian instrument.
1
H and
13
C NMR spectra chemical shi
s are reported as
d
values in ppm
relative to the residual solvent (CD
3
)
2
SO (2.50 ppm,
1
H, and
39.52 ppm,
13
C).
Tetramethylammonium 2,3,4,5,6-penta
uorophenolate was
synthesized and characterized as follows. Penta
uorophenol
(1.672 g, 9 mmol) was weighed out and added to a vial con-
taining 25% w/w tetra(
n
-methyl)ammonium hydroxide (3.298 g,
9 mmol) and methanol (2 mL). This mixture was stirred at room
temperature overnight. The resulting solution was dried using
a rotary evaporator and then dried further on a high vacuum
pump on a Schlenk line overnight. The product is a
ne white
powder. The product was stored in a nitrogen atmosphere until
use, which involved air exposure during the dissolution in water
to create the sorbent media. Yield: 2.259 g (97%).
1
H NMR (600
MHz
d
-DMSO)
d
3.14 (TMA) ppm.
13
C{
1
H} NMR (151 MHz,
d
-
DSMO)
d
147.8 (tt,
J
=
14.1, 4.0 Hz), 140.9 (dtdd,
J
=
231.9, 9.2,
4.6, 1.9 Hz), 138.6 (ddtd,
J
=
235.9, 19.2, 10.6, 2.3 Hz), 123.7 (dtt,
J
=
222.4, 14.8, 5.4 Hz), 54.4
54.3 (m, TMA) ppm.
13
C{
1
H} NMR
(151 MHz, D
2
O)
d
142.0
141.7 (m), 140.8 (dm,
J
=
231.6 Hz),
138.2 (dm,
J
=
240.7 Hz), 129.8 (dm,
J
=
232.4 Hz), 55.3
55.2 (m,
TMA) ppm.
19
F{
1
H} (565 MHz,
d
-DMSO)
d
172.0
172.1 (m, 2F),
172.1
172.3 (m, 2F),
196.3
196.5 (m, 1F) ppm. FTIR (ATR)/
cm
1
v
=
3032.41 (w), 1690.86 (w), 1644.75 (w), 1599.17 (w),
1504.13 (s), 1487.98 (s), 1467.75 (s), 1248.42 (m), 1230.19 (m),
1167 (w), 1084.29 (w), 1046.34 (w), 1001.62 (s), 967.89 (s), 723.23
(w), 604.91 (w), 577.75 (w).
Conclusions
We present an automated instrument for characterization of
carbon dioxide capture from a headspace into liquid sorbent
media. The instrument interfaces sorption characterization
with automated preparation of the liquid sorbent and head-
space gas, as well as extension of the instrument for subsequent
characterization of the liquid and gas. Characterization of
aqueous tetramethylammonium penta
uorophenoxide
revealed an apparent binding constant (on a pressure basis) of
1.35, demonstrating deployment of the instrument to charac-
terize novel sorbent
solvent combinations, a critical compo-
nent of a materials acceleration platform for accelerating the
development of carbon capture, concentration, and utilization
technologies.
Data availability
The instrument control so
ware is available at
https://
github.com/High-Throughput-Experimentation/helao-async
,
with dependencies in
https://github.com/High-Throughput-
Experimentation/helao-core
. The computer drawings of the
instrument, instrumentation control so
ware (helao
snapshot), the data
les acquired for the present work, and
the source code for the analysis and plotting of those data are
provided
via
CaltechData at
https://data.caltech.edu/records/
5z5zz-m9r81
(doi:
10.22002/5z5zz-m9r81
). The license for the
CCSI hardware is included alongside the design
les in that
repository, as well as a ESI document
for this manuscript.
Author contributions
R. J. J. and J. M. G. designed the CCSI with input from J. Y. Y.,
A. M. A., and J. A. H. R. J. J. and K. K. assembled and validated
the CCSI. R. J. R., K. K., and D. G. developed the instrument
control so
ware with validation experiments by K. K. and Y. L.
Y. L. operated CCSI and analyzed its data. C. L. and N. M. R.
synthesized and characterized the phenoxide sorbent under
supervision of J. Y. Y. J. M. G. was the primary author of the
manuscript with contributions from all authors. R. J. R, K. K.,
and Y. L. were the primary authors of the assembly and opera-
tion instructions.
Con
fl
icts of interest
A patent application for the CCSI has been
led. J. M. G. is an
industrial consultant for experiment automation.
Acknowledgements
This material is based upon work performed by the Center for
Closing the Carbon Cycle, which is supported by the U.S.
Department of Energy, O
ffi
ce of Science, O
ffi
ce of Basic Energy
Sciences Energy Frontier Research Centers program under
Award Number DE-SC0023427.
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