Abstract
Supported amines are a promising class of CO2sorbents offering large uptake capacities and fast uptake rates. Among supported amines, poly(ethyleneimine) (PEI) physically impregnated in the mesopores of SBA-15 silica is widely used. Within these composite materials, the chain dynamics and morphologies of PEI strongly influence the CO2capture performance, yet little is known about chain and macromolecule mobility in confined pores. Here, we probe the impact of the support-PEI interactions on the dynamics and structures of PEI at the support interface and the corresponding impact on CO2uptake performance, which yields critical structure-property relationships. The pore walls of the support are grafted with organosilanes with different chemical end groups to differentiate interaction modes (spanning from strong attraction to repulsion) between the pore surface and PEI. Combinations of techniques, such as quasi-elastic neutron scattering (QENS), 1H T1-T2relaxation correlation solid-state NMR, and molecular dynamics (MD) simulations, are used to comprehensively assess the physical properties of confined PEI. We hypothesized that PEI would have faster dynamics when subjected to less attractive or repulsive interactions. However, we discover that complex interfacial interactions resulted in complex structure-property relationships. Indeed, both the chain conformation of the surface-grafted chains and of the PEI around the surface influenced the chain mobility and CO2uptake performance. By coupling knowledge of the dynamics and distributions of PEI with CO2sorption performance and other characteristics, we determine that the macroscopic structures of the hybrid materials dictate the first rapid CO2uptake, and the rate of CO2sorption during the subsequent gradual uptake stage is determined by PEI chain motions that promote diffusive jumps of CO2through PEI-packed domains.
| Original language | English |
|---|---|
| Pages (from-to) | 11664-11675 |
| Number of pages | 12 |
| Journal | Journal of the American Chemical Society |
| Volume | 144 |
| Issue number | 26 |
| DOIs | |
| State | Published - Jul 6 2022 |
Funding
This work was supported by UNCAGE-ME, a U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES) Energy Frontier Research Center. This work was also supported by the U.S. DOE, Office of Science, BES, Materials Science and Engineering Division (NMR Interpretation and Analysis; via subcontract from LLNL). Work at ORNL’s Spallation Neutron Source is supported by the U.S. Department of Energy, Office of Basic Energy Sciences. Oak Ridge National Laboratory is managed by UT-Battelle, LLC, for U.S. DOE under Contract No. DEAC05-00OR22725. Access to the HFBS was provided by the Center for High Resolution Neutron Scattering, a partnership between the NIST and the NSF under agreement no. DMR-2010792. Certain commercial material suppliers are identified in this article to foster understanding. Such identification does not imply recommendation or endorsement by NIST, nor does it imply that the materials or equipment identified are necessarily the best available for the purpose. The computational/simulations aspect of this work was performed at the Center for Nanophase Materials Sciences, a U.S. Department of Energy Office of Science User Facility. This research also used resources of the Oak Ridge Leadership Computing Facility, which is a DOE Office of Science User Facility supported under Contract DEAC05-00OR22725. Solid-state NMR experiments were conducted at the Georgia Tech NMR Center. H.J.M. was additionally supported by Kwanjeong Educational Foundation.
| Funders | Funder number |
|---|---|
| UNCAGE-ME | |
| National Science Foundation | DMR-2010792 |
| U.S. Department of Energy | |
| National Institute of Standards and Technology | |
| Office of Science | |
| Basic Energy Sciences | |
| Lawrence Livermore National Laboratory | |
| Oak Ridge National Laboratory | DEAC05-00OR22725 |
| Kwanjeong Educational Foundation |
