Polyethylenimine “Snow”: An Emerging Material for Efficient Carbon Removal Xingguang Xu,* ,† Bobby Pejcic, † Charles Heath, † Matthew B Myers, † Cara Doherty, ‡ Yesim Gozukara, ‡ and Colin D. Wood* ,†,§ † Energy Business Unit, Commonwealth Scientific Industrial Research Organisation (CSIRO), Kensington, Perth, WA 6151, Australia ‡ Manufacturing Business Unit, Commonwealth Scientific Industrial Research Organisation (CSIRO), Clayton, Melbourne, VIC 3168, Australia § Curtin University of Science and Technology, Curtin Oil and Gas Innovation Centre (COGIC), Kensington, Perth, WA 6151, Australia * S Supporting Information ABSTRACT: Amine-functionalized solid adsorbents are one of the most promising alternatives to the conventional “amine scrubbing” for carbon capture with a number of prominent examples being reported. However, their widespread application in industry is unfulfilled due to their overall performance and complex fabrication, which relies on a porous support. In this “proof of concept” study, we report an approach for generating a new type of material called polyethylenimine (PEI) ‘snow’, which can be prepared for use in under 15 min. The material does not require a support, and the resulting CO 2 uptake is the highest reported to date for PEI-functionalized materials. This was achieved through a rigorous material program that identified conditions where a material with the requisite properties could be generated. From experimental measurements, the virtual dryness of the PEI snow results in fast CO 2 absorption kinetics, which is comparable to conventional solid adsorbents, but its CO 2 uptake (451.5 mg CO 2 /g PEI) is the highest reported so far. Breakthrough curves demonstrate the outstanding CO 2 selectivity over N 2 and CH 4 (above 1000), with the potential for post-combustion capture and natural gas sweeting. This strategy can be applied in affordable and efficient gas treatment for various large point sources. KEYWORDS: carbon capture, polyethylenimine, cross-linking, CO 2 uptake, breakthrough experiment, rapid preparation 1. INTRODUCTION The consumption of fossil fuels including coal, natural gas, and crude oil has escalated the atmospheric concentration of CO 2 , which is one of the principal greenhouse gases. 1-6 Hence, reduction of CO 2 emissions has become essential, which has resulted in an abundance of research on this topic. One of the most promising strategies is to capture the CO 2 released from various large point sources, for instance, coal-fired power plants. 7,8 To date, “amine scrubbing” remains the predominant technique in the carbon capture industry due to its high reactivity, high selectivity, and relatively low cost. 9 However, this benchmark technique suffers from few intrinsic drawbacks, including poor absorption efficiency, loss of the volatile amine, corrosion, and potential environmental and health concerns. Therefore, alternative approaches are being sought with one of the most promising approaches amine-functionalized solid adsorbents, which have attracted enormous attentions in recent years. 10-13 These adsorbents are typically prepared by impregnating or grafting amines onto the pore surface of highly porous supports such as activated carbon, silica gel, and various nanoparticles. For example, one of the earliest studies using polyethylenimine (PEI) reported was “molecular baskets” where PEI was loaded onto the surface of the mesoporous molecular sieve MCM-41. 14 Since then, PEI-functionalized solid adsorbents have been extensively investigated by different groups. For example, Chen et al. reported the preparation of PEI-modified resins that had a higher CO 2 uptake than any other existing PEI-loaded porous materials under a simulated flue gas condition (129.7 mg/g) and ambient conditions (99.3 mg/g). 15 Many other PEI-functionalized materials have also been developed recently, and research on this subject is rapidly growing. 16-23 However, most of these adsorbents exhibit few inherent drawbacks. First, their synthesis is usually complex, which not only increases material costs but also inhibit large scale production. 15 Second, low molecular weights PEI (Mw 600 and 800) are widely used to enhance the CO 2 diffusion in the pore space. However, leaching of PEI with relatively low molecular weights would always occur under humid con- ditions. 11 Furthermore, the highly porous PEI-functionalized CO 2 adsorbents usually have fairly low volumetric den- sities. 18,20,22 Accordingly, the size of the absorber column would increase to compensate for this. In addition, some of these adsorbents lose their adsorption capacities in the presence of water vapor. 23 Received: April 4, 2019 Accepted: July 10, 2019 Research Article www.acsami.org Cite This: ACS Appl. Mater. Interfaces XXXX, XXX, XXX-XXX © XXXX American Chemical Society A DOI: 10.1021/acsami.9b05921 ACS Appl. Mater. Interfaces XXXX, XXX, XXX-XXX Downloaded via UNIV OF SOUTHERN INDIANA on July 20, 2019 at 08:52:07 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.