About

Joan Brennecke is a professor whose research interests include gas solubility in ionic liquids. She holds a Ph.D. in Chemical Engineering from the University of Notre Dame, obtained in 2019, and a B.S. in Chemical Engineering from the University of Tulsa, earned in 2013. Her work focuses on the application of ionic liquids for various separation processes, including gas separation and CO2 capture. She is actively involved in leading research groups at UT Austin, contributing to advancements in the understanding and development of ionic liquid systems for industrial and environmental applications.

Research topics

• Chemistry
• Computer Science
• Artificial Intelligence
• Physical chemistry
• Thermodynamics
• Machine Learning
• Organic chemistry
• Inorganic chemistry
• Physics
• Materials science
• Biological system

Selected publications

• Physical Absorption of CO _<b>2</b> , CH _<b>4</b> , and N _<b>2</b> in Nine Imidazolium-Based Ionic Liquids

  Industrial & Engineering Chemistry Research · 2025-10-15 · 2 citations

  articleSenior authorCorresponding

  Ionic liquids (ILs) are promising alternative candidates for CO2 capture due to their negligible vapor pressure and the tunability of their cation–anion pairs, enabling precise control over solvent properties to meet specific performance demands. While ILs have been widely studied for CO2 absorption, limited data on CH4 and N2 solubilities make it challenging to identify selective ILs for CO2/CH4 and CO2/N2 separations. We evaluated nine imidazolium-based IL candidates ([1O2O1mim][Tf2N], [bmim][Tf2N], [bmim][DCA], [bmim][TfO], [bmim][SCN], [bmim][NO3], [bmim][TCM], [amim][DCA], and [amim][TCM]), all of which engage in purely physical gas sorption. In addition to the CO2 solubility, we measured CH4 and N2 solubility in these ILs using a gravimetric apparatus at pressures up to 140 bar, all at 308.2 K. From this data, we determined pure gas CO2/CH4 and CO2/N2 solubility selectivities. The choice of cation and anion has a much larger effect on CH4 and N2 solubility than on CO2 solubility. This indicates that selectivity enhancements can be more effectively achieved by suppressing N2 and CH4 solubility rather than increasing CO2 solubility. Notably, cyano-anion-based ILs that have small molar volumes exhibit high CO2/CH4 and CO2/N2 solubility selectivities, up to 27 ± 3 and 134 ± 32, respectively. Additionally, these ILs have viscosities as low as 12 mPa·s at 308.2 K, compared to ILs containing fluorinated anions with viscosities as high as 60 mPa·s at the same temperature. The pure gas CO2/CH4 solubility selectivities of several of the ILs investigated are comparable to or higher than those of conventional solvents like SelexolTM, Purisol®, Rectisol®, Fluor SolventTM, and sulfolane.

  PublisherDOI

• Vapor–Liquid Equilibria of Water and Amine-Functionalized Ionic Liquids

  Journal of Chemical & Engineering Data · 2025-06-28 · 2 citations

  articleSenior authorCorresponding

  Water is present in many carbon dioxide (CO2)-rich streams, such as air and postcombustion flue gas, for which carbon capture treatment is desirable. For nonaqueous solvents, such as ionic liquids (ILs), water can drastically affect CO2 absorption. For a particularly promising class of ILs for carbon capture, those with aprotic N-heterocyclic anions (AHAs), the effect of water on CO2 capture has been characterized, but the water loading of the AHA ILs as a function of relative humidity is not known. We performed gravimetric vapor–liquid equilibrium (VLE) measurements at 308.2 K for triethyl(octyl)phosphonium 4-nitropyrazolide ([P2228][4-NO2Pyra]), 3-(trifluoromethyl)pyrazolide ([P2228][3-CF3Pyra]), 2-cyanopyrrolide ([P2228][2-CNPyr]), 4-bromopyrazolide ([P2228][4-BrPyra]), and bis(trifluoromethylsulfonyl)imide (a non-AHA) ([P2228][Tf2N]), as well as trihexyl(tetradecyl)phosphonium 2-cyanopyrrolide ([P66614][2-CNPyr]) for water activities from 0.05 to 0.90. These VLE data were fit with the nonrandom two liquid (NRTL) activity coefficient model. The highly basic [P2228][4-BrPyra] was the most hydrophilic. [P66614][2-CNPyr], with its bulkier hydrocarbon chains, was much less hydrophilic than [P2228][2-CNPyr]. Three of the IL–water mixtures exhibited liquid–liquid equilibrium (LLE) at 308 K, with water solubility in the IL-rich phase ranging from 0.15 mole fraction for [P2228][Tf2N] to 0.95 mole fraction for [P2228][4-NO2Pyra].

  PublisherDOI

• Progress in high-pressure CO2–ionic liquid–organic compound phase equilibria and their applications: A review

  Separation and Purification Technology · 2025-10-31

  review
  PublisherDOI

• Supported ionic liquid membranes (SILMs) with exceptional selectivity and permeability for dilute CO2 separations

  Journal of Membrane Science · 2025-04-08 · 11 citations

  articleOpen accessCorresponding

  Supported ionic liquid membranes (SILMs), containing phosphonium ionic liquids with aprotic N -heterocyclic anions (AHA ILs) in an inert inorganic support, were tested under both dry and humidified (40 % RH) mixed-gas conditions down to 420 ppm CO 2 in N 2 at 35 °C. In the dry case, the best performing IL, triethyl(octyl)phosphonium 4-bromopyrazolide ([P 2228 ][4-BrPyra]) exhibited mixed-gas CO 2 permeabilities and CO 2 /N 2 permeability selectivities as high as 26,800 barrer and 7,000, respectively. In the presence of humidity, the CO 2 permeability and CO 2 /N 2 selectivity increased to 49,100 barrer and 13,200, respectively, and these are the highest reported combination in the literature. Humidity amplifies CO 2 permeabilities and CO 2 /N 2 permeability selectivities through increases in CO 2 capacity due to bicarbonate formation and through faster mobility of the mobile carrier from decreased viscosity . N 2 permeability stayed roughly invariant in the presence of humidity, likely from competing effects of viscosity reduction and lower N 2 solubility. • SILMs exhibit dual-mode facilitated transport membrane behavior. • Humidity enhanced CO 2 permeability and CO 2 /N 2 selectivity for all AHAs. • SILMs achieve CO 2 /N 2 selectivity of 13,200 at 420 ppm CO 2 . • SILMs achieve CO 2 permeability of 49,100 barrer at 420 ppm CO 2 .

  PublisherDOI

• Effect of Water on the Viscosity, Density, and Ionic Conductivity of Ionic Liquids with Aprotic <i>N</i> -Heterocyclic Anions

  Journal of Chemical & Engineering Data · 2025-12-15

  articleSenior authorCorresponding

  Aprotic N-heterocyclic anion (AHA) ionic liquids (ILs) are promising solvents for carbon capture due to their high CO2 capacities at low partial pressures and tunability. However, water, a common contaminant, significantly affects the thermophysical properties of ILs. We investigate the effects of varying water loadings on the density, viscosity, and ionic conductivity of four AHA ILs: 4-nitropyrazolide [4-NO2Pyra]−, 3-(trifluoromethyl)pyrazolide [3-CF3Pyra]−, 2-cyanopyrrolide [2-CNPyr]−, and 4-bromopyrazolide [4-BrPyra]−, each paired with triethyl(octyl)phosphonium cation, [P2228]+. Density and viscosity were measured from 293.13 to 333.13 K. All AHA ILs exhibited ideal volumetric mixing, with mixture densities lying between those of the pure components. At higher water loadings (>17 wt %), viscosities of AHA IL + water mixtures were less than one-fifth the values of the pure ILs. We found that pairing the bulkier trihexyl(tetradecyl)phosphonioum [P66614]+ cation with [2-CNPyr]− resulted in a greater decrease in viscosity relative to the neat IL compared to the [P2228]+ cation. Finally, ionic conductivities at 298.15 K peaked near water mole fractions of 0.98–0.99 (up to 1.967 S/m for [P2228][2-CNPyr]), and the Walden Plot indicates that as water content increases, the ions ([P2228]+ and AHA) become more dissociated.

  PublisherDOI

• Pressure-stable supported ionic liquid membranes using isoporous supports for evaluating pure- and mixed-gas light paraffin fractionation

  Journal of Membrane Science · 2025-09-11

  articleCorresponding
  PublisherDOI

• Poly(1,3-dioxolane)-containing terpolymer membranes for CO2 separations

  Journal of Membrane Science · 2025-10-24 · 2 citations

  article
  PublisherDOI

• Organic electrolyte cations promote non-aqueous CO2 reduction by mediating interfacial electric fields

  Nature Catalysis · 2025-01-10 · 71 citations

  article
  PublisherDOI

• Interfacial Cation Arrangement Controls Electrocatalytic Kinetics in CO ₂ Reduction

  Journal of the American Chemical Society · 2025-12-18

  article

  The identity of electrolyte cations is known to strongly influence electrocatalytic activity, but the relationship between their interfacial arrangement and observed performance remains poorly understood. Organic cations, with their molecular tunability, provide a powerful platform for systematically probing these effects. Here, we leverage phosphonium-based geminal dications to control interfacial cation arrangement and identify the variables that most strongly influence catalytic rates. As a case study, we examine CO2 reduction to CO over polycrystalline silver electrodes in dry aprotic acetonitrile. Through a combination of rotating disk electrode measurements, electrochemical impedance spectroscopy, and molecular dynamics simulations, we decouple the effects of cation–electrode distance and interfacial cation density on catalytic rates. We find that smaller, more densely packed cations induce stronger interfacial electric fields, which lower the activation barrier for CO2 adsorption and increase reaction rates. Using geminal phosphonium dications [Cn(Pmmm)2][ClO4]2, we demonstrate that both the vertical and lateral positioning of organic cations within the electrical double layer independently affect reactivity. These results demonstrate that electrolyte cation identity primarily influences catalytic kinetics by determining how efficiently charge can be arranged at electrochemical interfaces. Overall, our findings support an electrostatic view of cation effects in catalysis and provide design principles for next-generation electrolytes.

  PublisherDOI

• Interfacial Cation Arrangement Governs Electrocatalytic Kinetics in CO2 Reduction

  ChemRxiv · 2025-10-17

  preprint

  The identity of electrolyte cations is known to strongly influence electrocatalytic activity, but the relationship between their interfacial arrangement and catalytic performance remains poorly understood. Organic cations, with their molecular tunability, provide a powerful platform for systematically probing these effects. Here, we leverage phosphonium-based geminal di-cations to control interfacial cation arrangement and identify the variables that most strongly influence catalytic rates. As a case study, we examine CO2 reduction (CO2R) to CO over polycrystalline silver electrodes in dry aprotic acetonitrile. Through a combination of rotating disk electrode measurements, electrochemical impedance spectroscopy, and molecular dynamics simulations, we decouple the effects of cation–electrode distance and interfacial cation density on catalytic rates. We find that smaller, more densely packed cations induce stronger interfacial electric fields, which lower the activation barrier for CO2 adsorption and increase reaction rates. Using geminal phosphonium di-cations, we demonstrate that both the vertical and lateral positioning of organic cations within the electrical double layer independently influence reactivity. These results demonstrate that electrolyte cation identity primarily influences electrocatalytic kinetics by determining how efficiently charge can be arranged at the electrocatalytic interface. These findings support an electrostatic view of cation effects in catalysis and provide principles for designing next-generation electrolytes.

  PublisherDOI

Recent grants

• ECO-CBET: GOALI: Environmental Convergence in Chemical Process Systems - Integrating CO2 Capture and In-Situ Conversion with Ethylene Manufacture

  NSF · $1.7M · 2021–2026

Frequent coauthors

• David T. Allen

  Center for Environmental Health

  87 shared

• Phillip E. Savage

  Pennsylvania State University

  87 shared

• Prashant V. Kamat

  University of Notre Dame

  87 shared

• Peter J. Stang

  University of Utah

  86 shared

• Christopher A. Voigt

  Massachusetts Institute of Technology

  85 shared

• Paul J. Chirik

  85 shared

• Philip Proteau

  Oregon State University

  85 shared

• Gustavo E. Scuseria

  Rice University

  85 shared

Labs

• The Brennecke GroupPI

Education

• B.S., Chemical Engineering

  University of Texas at Austin

  1984

• M.S.

  University of Illinois

  1987

• Ph.D.

  University of Illinois

  1989

Awards & honors

• Ipatieff Prize – American Chemical Society (2001)
• Professional Progress Award – American Institute of Chemical…
• J. M. Prausnitz Award at the Eleventh International Conferen…
• Stieglitz Award – American Chemical Society (2008)
• E. O. Lawrence Award – Department of Energy (2009)