Microporous 2D indium metal-organic frameworks for selective CO2 capture and their application in the catalytic CO2-cycloaddition of epoxides.

ABSTRACT

Four new 2D indium metal-organic frameworks (MOFs) (Me2NH2)[In(SBA)2] (1), (Me2NH2)[In(SBA)(BDC)] (2), (Me2NH2)[In(SBA)(BDC-NH2)] (3), and (NH4)3[In3Cl2(BPDC)5] (4), (H2SBA = 4,4'-sulfonyldibenzoic acid; H2BDC = 1,4-benzenedicarboxylic acid; H2BDC-NH2 = 2-amino-1,4-benzenedicarboxylic acid; H2BPDC = 4,4'-biphenyldicarboxylic acid) have been synthesized under solvothermal reaction conditions for compounds 1 to 3 and the DES (deep eutectic solvent) reaction has been attempted for compound 4. The structure of these MOFs has been determined by using single crystal X-ray diffraction study and all of theses four 2D monolayer framework with porous properties. The N2 gas sorption measurements indicated that Brunauer-Emmer-Teller (BET) and Langmuir surface areas of compound 1 are 207 and 301 m2 g-1, respectively, which is probably the first one having substantial gas uptake properties in the entire 2D In-MOF family to date. Furthermore, these new indium MOFs on the addition of n-Bu4NBr were active for the cycloaddition of CO2 and propylene oxide, generating propylene carbonates in high conversions under mild conditions. Particularly, the most active MOF 4 was found to efficiently couple CO2 with a series of terminal epoxides to give the corresponding cyclic organic carbonates with high selectivities.