Uncommon thioether-modified metal–organic frameworks with unique selective CO2 sorption and efficient catalytic conversion

Abstract

Two new three-dimensional (3D) metal–organic frameworks (MOFs), namely {[Cu₂(L)(4,4′-bipy)(OH)]·H₂O}_n (1) and {[Mn₃(L)₂(4,4′-bipy)(DMA)₂]·H₂O}_n (2), were constructed by a newly synthesized thioether carboxylic acid ligand 5-((formic acid-3-sulfur)methyl)isophthalic acid (H₃L) and 4,4′-bipyridine (4,4′-bipy). Thioether bonds in H₃L can rotate freely in space, which are conducive in constructing MOFs with rich and stable structures. Simultaneously, the uncoordinated sulfur atoms affect the polarity of the framework and play an important role in adsorption. Gas adsorption results indicated that 1 can selectively adsorb CO₂ from the mixture of CH₄/CO₂. Moreover, due to the high catalytic activity of [Cu₄(COO)₆N₄O₂] clusters, 1 is also an excellent recyclable catalyst that can chemically fix CO₂ into cyclic carbonate under mild solvent-free conditions. Therefore, 1 may be explored as a dual-functional material for industrial adsorption and catalysis.