Smart adsorbents for CO2 capture: Making strong adsorption sites respond to visible light

Abstract

Due to the good controllability and high energy efficiency in adsorption processes, photoresponsive adsorbents are intriguing for CO 2 capture. Nevertheless, most reported photoresponsive adsorbents are designed based on weak adsorption sites, regulating CO 2 adsorption through structural change or steric hindrance. In addition, ultraviolet (UV) light is commonly involved in the regulation of adsorption capacity. Here we report for the first time the smart adsorbents for CO 2 capture, which makes strong adsorption sites respond to visible (Vis) light. The adsorbents were fabricated by introducing primary amine and Dispersed Red 1 (DR1, a kind of push-pull azobenzene that responds to Vis light rapidly) units to mesoporous silica, which act as strong adsorption sites and triggers, respectively. The primary amine sites make the adsorbents highly selective in the adsorption of CO 2 over CH 4. Without light irradiation, azobenzene is in the form of trans configuration, which leads to decreased electrostatic potential of primary amines and subsequently, exposure of active sites and liberal adsorption of CO 2. Upon Vislight irradiation, cis isomers are formed, which results in increased electrostatic potential of primary amines and subsequently shelter of active sites. Even on such strong adsorption sites, the alteration of CO 2 adsorption capacity can reach 40% for the adsorbent with and without Vis-light irradiation. Moreover, the trans/cis isomerization of DR1 units can be triggered reversibly by Vis light. The present smart system endows adsorbents with selective adsorption capacity and avoids the employment of UV light, which is unlikely to be achieved by conventional photoresponsive adsorbents.

Efficient N-Doped Porous Carbonaceous CO2 Adsorbents Derived from Commercial Urea-Formaldehyde Resin

“…On the industrial scale, the majority CO 2 emission from flue gas into the atmosphere has been mostly captured by aqueous amine scrubbing due to the mature process and low cost . However, its widespread implementation has been inhibited by the parasitic energy consumption through solvent regeneration, high toxicity together with equipment corrosion in the regeneration process. , To overcome those issues, the CO 2 capture using solid adsorbents is an attractive alternative thanks to its low energy consumption, facile operation, and ease for practical applications. , Therefore, the scientific and industrial communities have focused on the advancement of solid-state adsorbents with low energy requirements and easy reversibility for efficient CO 2 adsorption. For this purpose, numerous adsorbents such as porous carbons, ,− zeolites, porous polymers, − covalent organic frameworks (COFs), and metal–organic frameworks (MOFs) , have been widely investigated in the past decades.…”

Evaluation of adsorbent materials for carbon dioxide capture

“…In this regard, novel smart adsorbents were synthesized by modification of target-specific chemical active sites (that avoid the employment of ultraviolet light) through introduction of primary and secondary amines into azobenzene functionalized metal-organic frameworks for tunable carbon capture [27,[29][30][31]. The target-specific amine sites render the adsorbent significantly selective in carbon capture from gas mixtures, and the azobenzene groups act as light-responsive switches to influence the adsorbent-adsorbate interactions.…”

Process-Oriented Smart Adsorbents: Tailoring the Properties Dynamically as Demanded by Adsorption/Desorption

“…DFT calculations indicate that the adsorption behavior originates from the interplay between azobenzene and amine within the pores of the adsorbent. Such adsorption behavior also appears in the POSAs modified with azobenzene and different amines. − Consequently, by utilizing the synergistic interaction between azobenzenes and amines, selective adsorption for CO 2 is achieved, and moreover, the energy consumption of desorption is reduced as well.…”