The fixation of carbon dioxide with epoxides catalyzed by cation-exchanged metal-organic framework

Metal-organic frameworks (MOFs) possess high porosity and specific surface area and have been extensively applied in the capture and separation of CO2 from flue gas or natural gas. UTSA-16 is the second highest porous MOF for CO2 capture, which is attributed to its microporous structure with anatase type and the fact that the K+ species located in the channel can interact with CO2 molecule. Herein, a sequence of alkali metal cation-exchanged UTSA-16 (hereinafter denoted as M-UTSA-16, M = Li, Na, K, Rb, Cs) were prepared and evaluated for CO2 capture. The CO2 adsorption isotherms of M-UTSA-16 obtained at 273K and 298K showed that the adsorption capacity for CO2 decreased in the sequence of K+>Na+>Li+>Rb+>Cs+. The series of M-UTSA-16 were used as the catalyst for the transformation of CO2 and epoxide to cyclic carbonate in the absence of co-catalyst. Li-UTSA-16 exhibited the highest efficiency of catalytic activity compared with other M-UTSA-16. The result was inconsistent with the sequence of CO2 adsorption capacity. The further systematic investigation showed that the decreasing order of catalytic activities of M-UTSA-16 was in agreement with the sequence of increasing radius of the exchanged cations as well as the heat of adsorption for CO2 at lower pressure region. (C) 2017 Elsevier Inc. All rights reserved.