Controllable CO₂ Capture in Metal–Organic Frameworks: Making Targeted Active Sites Respond to Light

Abstract

Light-responsive metal−organic frameworks (LMOFs) are intriguing materials for CO 2 capture owing to their tunable structures and performances. However, conventional LMOFs are reported to regulate CO 2 adsorption capacity by steric hindrance or structural variation because of the weak affinity between the adsorbate and adsorbent. Developing efficient LMOF-based adsorbents with strong but tunable active sites for controllable CO 2 capture is an extremely desirable yet challenging task. In this work, we constructed an LMOF-based adsorbent with targeted adsorption sites by incorporating polyethyleneimine into an azobenzene-decorated LMOF for controllable CO 2 capture. The targeted active sites of amines endow the adsorbent with enhanced selectivity in the capture of CO 2 . Additionally, the surface electrostatic potential around amines can be regulated by the isomerization of azobenzene moieties upon light irradiation. Moreover, the reversible light irradiation generates the adsorbents with exposed/sheltered adsorption sites for the controllable capture of CO 2 on amines. The present work encourages us to develop novel LMOF-based adsorbents for controllable adsorption separation, which is hard to realize by conventional LMOFs.

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

“…Furthermore, the excellent reversibility of POSAs was demonstrated by three trans / cis isomerization cycles. Analogously, such CO 2 adsorption behavior can also be achieved in an azobenzene-decorated MIL-101-type MOF with incorporated polyethylenimine as adsorption sites (P n /azoMOF) . In addition, we synthesized another POSA, A m P n @MS, by introducing azobenzene and amine into the pores of mesoporous silica simultaneously .…”

“…Analogously, such CO 2 adsorption behavior can also be achieved in an azobenzenedecorated MIL-101-type MOF with incorporated polyethylenimine as adsorption sites (P n /azoMOF). 47 In addition, we synthesized another POSA, A m P n @MS, by introducing azobenzene and amine into the pores of mesoporous silica simultaneously. 3 The adsorption capacity for CO 2 of the adsorbents changes significantly with the isomerization of azobenzenes.…”

Photoresponsive Metal-Organic Frameworks as Adjustable Scaffolds in Reticular Chemistry

“…Azobenzenes are postulated as convenient scaffolds to induce a photoresponsive behavior in condensed materials through easy isomerization between both geometric isomers [58]. The employment of azobenzene-based compounds as organic ligands in the preparation of MOFs led to different applications such as control over the pore (open/close pore) [59] or capture and release of carbon dioxide [60,61]. Professors Liu, Sun and colleagues prepared azobenzene-functionalized UiO-66 absorbents [62].…”

Green Chemistry and Process Intensification: Milestones on a Sustainable Development

“…BECCS can eliminate 300-850 kg of CO2 equivalents from the atmosphere per megawatt-hour of electrical output (kg/MWhe), rendering it superior to other low carbon techniques and allowing the offset of emissions from hard-to-abate industries. Focusing on efficacious materials for carbon capture, Jiang, et al [35] noticed the expansion of light-responsive metal−organic frameworks (LMOFs) that possess tunable structures and performances. Whilst traditional amines could not attain controllable adsorption separation, such LMOFs possess tunable amine-based active sites that ameliorate CO2 capture and control adsorption and separation.…”

“…Some progresses as well call attention to the enhancement of techniques for decrease of CO2 founded on electrocatalytic techniques, comprising the employment of Ru and Re catalysts [36] and the usage of ionic liquids for such implementation [37] as well as investigation of Earthabundant iron catalysts [38]. Complementary to electrochemical processes, enzymatic [39] and photocatalytic [35] techniques are as well proved to possess a position in the toolbox for conversion and usage of CO2 [2].…”