Evaluation of CO₂and H₂O Adsorption on a Porous Polymer Using DFT and In Situ DRIFT Spectroscopy

Abstract

Numerous hyper-cross-linked polymers (HCPs) have been developed as CO 2 adsorbents and photocatalysts. Yet, little is known of the CO 2 and H 2 O 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 CO 2 and H 2 O adsorption sites on a triazine−biphenyl HCP. We found that CO 2 and H 2 O adsorb on the same HCP sites albeit with different adsorption strengths. The primary amines of the triazines were identified as favoring strong CO 2 binding interactions. Given the potential use of HCPs for CO 2 photoreduction, we also investigated CO 2 and H 2 O adsorption under transient light irradiation. Under irradiation, we observed partial CO 2 and H 2 O desorption and a redistribution of interactions between the H 2 O and CO 2 molecules that remain adsorbed at HCP adsorption sites.

Impact of Interfaces, and Nanostructure on the Performance of Conjugated Polymer Photocatalysts for Hydrogen Production from Water

“…These studies provide some valuable data on what likely occurs at the interface between the organic semiconductors and aqueous media during photocatalysis. Exploring this further, a recent study investigated H 2 O adsorption onto a porous hyper-crosslinked polymer (HCP) consisting of a triazine monomer and a biphenyl monomer [ 130 ]. A combination of density functional theory (DFT) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was used to analyze potential adsorption sites and describe the adsorption of H 2 O vapor to interact with both the triazine and biphenyl unit but more strongly with the latter [ 130 ].…”

“…Exploring this further, a recent study investigated H 2 O adsorption onto a porous hyper-crosslinked polymer (HCP) consisting of a triazine monomer and a biphenyl monomer [ 130 ]. A combination of density functional theory (DFT) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was used to analyze potential adsorption sites and describe the adsorption of H 2 O vapor to interact with both the triazine and biphenyl unit but more strongly with the latter [ 130 ]. Whilst this material is a HCP, the principle of this process could be applied in the context of photocatalytic water splitting with conjugated materials in order to understand design principles based on favorable interactions at the interface.…”