Measurement of Physicochemical Properties and CO2, N2, Ar, O2, and H2O Unary Adsorption Isotherms of Purolite A110 and Lewatit VP OC 1065 for Application in Direct Air Capture

Direct air capture (DAC) using solid adsorbents has gained significant attention as a carbon dioxide removal (CDR) technology to help limit global temperature rise to below 2 °C. One large area of focus is the development of new adsorbent materials for DAC. However, the necessary data needed to employ these materials in process models for adsorbent screening are rarely available. Here, we showcase Purolite A110, a commercially available amine-functionalized polymeric resin, as a new candidate adsorbent for DAC and compare its properties to a current benchmark, Lewatit VP OC 1065. For both materials, we report their chemical features and composition, skeletal, particle, and bed density, total pore volume, particle porosity, BET area, thermal stability, and specific heat capacity. We determine their equilibrium sorption properties by measuring the volumetric CO2 isotherms at 288, 298, 308, 333, 343, 353, and 393 K, N2 and H2O isotherms at 288, 298, and 308 K, and Ar and O2 isotherms at 298 K. For CO2, N2, and H2O, we also present the corresponding isotherm model fitting parameters and heats of adsorption. These data can help facilitate process modeling and optimization studies to properly assess these adsorbents at scale.

Fabrication of graded porous structure of hydroxypropyl cellulose hydrogels via temperature-induced phase separation

A novel hydroxypropyl cellulose (gHPC) hydrogel with graded porosity has been fabricated, in which pore size, shape, and mechanical properties vary across the material. The graded porosity was achieved by cross-linking different parts of the hydrogel at temperatures below and above 42 °C, which was found to be the temperature of turbidity onset (lower critical solution temperature, LCST) for the HPC and divinylsulfone cross-linker mixture. Scanning electron microscopy imaging revealed a decreasing pore size along the cross-section of the HPC hydrogel from the top to the bottom layer. HPC hydrogels demonstrate graded mechanical properties whereby the top layer, Zone 1, cross-linked below LCST, can be compressed by about 50% before fracture, whereas the middle and bottom layers (Zone 2 and 3, respectively) cross-linked at 42 °C, can withstand 80% compression before failure. This work demonstrates a straightforward, yet novel, concept of exploiting a graded stimulus to incorporate a graded functionality into porous materials that can withstand mechanical stress and minor elastic deformations.

A Robust and Low-Cost Sulfonated Hypercrosslinked Polymer for Atmospheric Water Harvesting

The availability of freshwater is rapidly declining due to over-exploitation and climate change, with multiple parts of the globe already facing significant freshwater scarcity. Here, a sulfonated hypercrosslinked polymer able to repeatedly harvest significant amounts of water via direct air capture is reported. Water uptake from relative humidities as low as 10% is demonstrated, mimicking some of the harshest environments on Earth. A water harvesting device is used to show repeated uptake and harvesting without significant detriment to adsorbent performance. Desorption is triggered using simulated sunlight, presenting a low-energy route to water harvesting and adsorbent regeneration. The synthesis of sulfonated hypercrosslinked polymer requires only low-cost and readily available reagents, offering excellent potential for scale-up. Due to an almost limitless supply of water vapor from air in most regions around the globe, this approach can transform our ability to address water security concerns.

Hyper crosslinked polymer supported NHC stabilized gold nanoparticles with excellent catalytic performance in flow processes

Highly active and selective heterogeneous catalysis driven by metallic nanoparticles relies on a high degree of stabilization of such nanomaterials facilitated by strong surface ligands or deposition on solid supports. In order to tackle these challenges, N-heterocyclic carbene stabilized gold nanoparticles (NHC@AuNPs) emerged as promising heterogeneous catalysts. Despite the high degree of stabilization obtained by NHCs as surface ligands, NHC@AuNPs still need to be loaded on support structures to obtain easily recyclable and reliable heterogeneous catalysts. Therefore, the combination of properties obtained by NHCs and support structures as NHC bearing "functional supports" for the stabilization of AuNPs is desirable. Here, we report the synthesis of hyper-crosslinked polymers containing benzimidazolium as NHC precursors to stabilize AuNPs. Following the successful synthesis of hyper-crosslinked polymers (HCP), a two-step procedure was developed to obtain HCP·NHC@AuNPs. Detailed characterization not only revealed the successful NHC formation but also proved that the NHC functions as a stabilizer to the AuNPs in the porous polymer network. Finally, HCP·NHC@AuNPs were evaluated in the catalytic decomposition of 4-nitrophenol. In batch reactions, a conversion of greater than 99% could be achieved in as little as 90 s. To further evaluate the catalytic capability of HCP·NHC@AuNP, the catalytic decomposition of 4-nitrophenol was also performed in a flow setup. Here the catalyst not only showed excellent catalytic conversion but also exceptional recyclability while maintaining the catalytic performance.

Evaluation of CO2 and H2O Adsorption on a Porous Polymer Using DFT and In Situ DRIFT Spectroscopy

Numerous hyper-cross-linked polymers (HCPs) have been developed as CO₂ adsorbents and photocatalysts. Yet, little is known of the CO₂ and H₂O adsorption mechanisms on amorphous porous polymers. Gaining a better understanding of these mechanisms and determining the adsorption sites are key to the rational design of improved adsorbents and photocatalysts. Herein, we present a unique approach that combines density functional theory (DFT), in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and multivariate spectral analysis to investigate CO₂ and H₂O adsorption sites on a triazine-biphenyl HCP. We found that CO₂ and H₂O adsorb on the same HCP sites albeit with different adsorption strengths. The primary amines of the triazines were identified as favoring strong CO₂ binding interactions. Given the potential use of HCPs for CO₂ photoreduction, we also investigated CO₂ and H₂O adsorption under transient light irradiation. Under irradiation, we observed partial CO₂ and H₂O desorption and a redistribution of interactions between the H₂O and CO₂ molecules that remain adsorbed at HCP adsorption sites.

Hypercrosslinked Polymers as a Photocatalytic Platform for Visible-Light-Driven CO2 Photoreduction Using H2 O

The design of robust, high-performance photocatalysts is key for the success of solar fuel production by CO2 conversion. In this study, hypercrosslinked polymer (HCP) photocatalysts have been developed for the selective reduction of CO2 to CO, combining excellent CO2 sorption capacities, good general stabilities, and low production costs. HCPs are active photocatalysts in the visible light range, significantly outperforming the benchmark material, TiO2 P25, using only sacrificial H2 O. It is hypothesized that superior H2 O adsorption capacities facilitate access to photoactive sites, improving photocatalytic conversion rates when compared to sacrificial H2 . These polymers are an intriguing set of organic photocatalysts, displaying no long-range order or extended π-conjugation. The as-synthesized networks are the sole photocatalytic component, requiring no added cocatalyst doping or photosensitizer, representing a highly versatile and exciting platform for solar-energy conversion.

The design of hypercrosslinked polymers from benzyl ether self-condensing compounds and external crosslinkers

Hypercrosslinked polymers were produced via the self-condensation of benzyl ether compounds, providing a one-component route to highly porous networks and significant reductions in catalyst waste compared to conventional routes. These compounds also represent a new class of external crosslinkers, able to impart improved textural properties when compared to standard aliphatic crosslinkers.

Graphene-aramid nanocomposite fibres via superacid co-processing

The development of graphene-polymer nanocomposite materials has been hindered by issues such as poor colloidal stability of graphene in liquid media, weak interactions between graphene and the host polymers as well as the lack of scalable and economical graphene synthesis routes. Chlorosulfonic acid (CSA) can spontaneously disperse graphene without the need for mechanical agitation, chemical functionalisation or surfactant stabilisation,1 however is incompatible with most polymers and organic materials. Here, we demonstrate how poly(p-phenylene terephthalamide) (PPTA) - the polymer which constitutes Kevlar - can be co-processed with graphene in CSA and wet-spun into nanocomposite fibres with minimal aggregation of graphene.

Kinematic Modeling of Mechanocatalytic Depolymerization of α-Cellulose and Beechwood

Mechanocatalytic depolymerization of lignocellulose presents a promising method for the solid-state transformation of acidified raw biomass into water-soluble products (WSPs). However, the mechanisms underlining the utilization of mechanical forces in the depolymerization are poorly understood. A kinematic model of the milling process is applied to assess the energy dose transferred to cellulose during its mechanocatalytic depolymerization under varied conditions (rotational speed, milling time, ball size, and substrate loading). The data set is compared to the apparent energy dose calculated from the kinematic model and reveals key features of the mechanocatalytic process. At low energy doses, a rapid rise in the WSP yield associated with the apparent energy dose is observed. However, at a higher energy dose obtained by extended milling duration or high milling speeds, the formation of a substrate cake layer on the mill vials appear to buffer the mechanical forces, preventing full cellulose conversion into WSPs. By contrast, for beechwood, there exists a good linear dependence between the WSP yield and the energy dose provided to the substrate over the entire range of WSP yields. As the formation of a substrate cake in depolymerization of beechwood is less severe than that for the cellulose experiments, the current results verify the hypothesis regarding the negative effect of a substrate layer formed on the mill vials upon the depolymerization process. Overall, the current findings provide valuable insight into relationships between the energy dose and the extent of cellulose depolymerization effected by the mechanocatalytic process.

Noncovalent Surface Modification of Cellulose Nanopapers by Adsorption of Polymers from Aprotic Solvents

Basic adsorption of hydrophobic polymers from aprotic solvents was introduced as a platform technology to modify exclusively the surfaces of cellulose nanopapers. Dynamic vapor sorption demonstrated that the water vapor uptake ability of the nanopapers remained unperturbed, despite strong repellency to liquid water caused by the adsorbed hydrophobic polymer on the surface. This was enabled by the fact that the aprotic solvents used for adsorption did not swell the nanopaper unlike water that is generally applied as the adsorption medium in such systems. As case examples, the adsorptions of polystyrene (PS) and poly(trifluoroethylene) (PF₃E) were followed by X-ray photoelectron spectroscopy and water contact angle measurements, backed up with morphological analysis by atomic force microscopy. The resulting nanopapers are useful in applications like moisture buffers where repellence to liquid water and ability for moisture sorption are desired qualities.

High-Surface-Area, Emulsion-Templated Carbon Foams by Activation of polyHIPEs Derived from Pickering Emulsions

Carbon foams displaying hierarchical porosity and excellent surface areas of >1400 m²/g can be produced by the activation of macroporous poly(divinylbenzene). Poly(divinylbenzene) was synthesized from the polymerization of the continuous, but minority, phase of a simple high internal phase Pickering emulsion. By the addition of KOH, chemical activation of the materials is induced during carbonization, producing Pickering-emulsion-templated carbon foams, or carboHIPEs, with tailorable macropore diameters and surface areas almost triple that of those previously reported. The retention of the customizable, macroporous open-cell structure of the poly(divinylbenzene) precursor and the production of a large degree of microporosity during activation leads to tailorable carboHIPEs with excellent surface areas.

Developing a Comprehensive Animal Care Occupational Health and Safety Program at a Land-Grant Institution

The Public Health Service Policy on the Humane Care and Use of Laboratory Animals and sound ethical practices require institutions to provide safe working environments for personnel working with animals; this mandate is achieved in part by establishing an effective animal care Occupational Health and Safety Program (OHSP). Land-grant institutions often face unique organizational challenges in fulfilling this requirement. For example, responsibilities for providing health and safety programs often have historically been dispersed among many different divisions scattered around the campus. Here we describe how our institutional management personnel overcame organizational structure and cultural obstacles during the formation of a comprehensive campus-wide animal care OHSP. Steps toward establishing the animal care OHSP included assigning overall responsibility, identifying all stakeholders, creating a leadership group, and hiring a fulltime Animal Care OHSP Specialist. A web-based portal was developed, implemented, and refined over the past 7 y and reflected the unique organizational structures of the university and the needs of our research community. Through this web-based portal, hazards are identified, risks are assessed, and training is provided. The animal care OHSP now provides easy mandatory enrollment, supports timely feedback regarding hazards, and affords enrollees the opportunity to participate in voluntary medical surveillance. The future direction and development of the animal care OHSP will be based on the research trends of campus, identification of emerging health and safety hazards, and ongoing evaluation and refinement of the program.

Controlling responsive emulsion properties via polymer design

Subtle changes in copolymer surfactant architecture and chain-end functionality can induce diverse behaviours in pH-responsive branched copolymer-stabilized emulsions.