Facilely incorporating aliphatic amines into a hydroxyl-containing robust metal-organic framework for enhancing CO2 adsorption

Abstract

Two amine-incorporated composites, TETA@MIP-206-OH and TREN@MIP-206-OH, were facilely fabricated by incorporation of triethylenetetramine (TETA) and tris(2-aminoethyl)amine (TREN), respectively, into a hydroxyl-containing robust metal-organic framework, MIP-206-OH for enhancing CO2 adsorption. Characterizations revealed that the two amines were both successfully loaded into the pores by the interactions between the phenolic hydroxyl sites in the porous skeleton and the introduced amines groups without disrupting the inherent structure of MIP-206-OH. CO2 sorption experiments revealed that TETA@MIP-206-OH(1:1) possesses a CO2 adsorption capacity of 20.76 ± 2.3 cm3/g at 298 K and 1 atm, which is similar with that of MIP-206-OH itself (20.32 cm3/g) at the same condition. But, at relative lower pressure (P/P0 < 0.1), TETA@MIP-206-OH(1:1) exhibits much higher CO2 adsorption capacity that of MIP-206-OH itself, which finally is attributed to chemisorption feature verified by desorption hysteresis and Fourier transform infrared spectra measurements. TREN@MIP-206-OH(10:1) exhibits a higher CO2 adsorption capacity than both of them not only at lower pressure (P/P0 < 0.1) but also at about 1 atm with a value of 35.07 ± 0.59 cm3/g at 298 K. Moreover, the recycle sorption experiments revealed TETA@MIP-206-OH(1:1) composite can be reused for CO2 adsorption after being reactivated by heating, while the loaded aliphatic amines were still well immobilized in the framework even after running ten cycles of the CO2 sorption experiments. This work successfully demonstrated that incorporating aliphatic amines into hydroxyl-containing porous materials by simple acid-base interactions, effective recyclable adsorbents for CO2 capture can be facilely achieved.