Co(II)-tricarboxylate metal–organic frameworks constructed from solvent-directed assembly for CO2 adsorption

Abstract

A series of Co(II)-tricarboxylate metal–organic frameworks (MOFs), {Co3O(HBTC)2(H2O)(DMF)}n (1), {Co2(BTC)Cl(DEF)3}n (2), {Co3O(BTB)2(DMF)·2(N(CH3)2)·(H2O)}n (3), and {Co3(HCOO)(BTB)2 (DEF)·(N(C2H5)2)}n (4) (BTC = 1,3,5-benzenetricarboxylate, BTB = 4,4′,4″-benzene-1,3,5-triyltribenzoate, DMF = N,N′-dimethylformamide, DEF = N,N′-diethylformamide), were synthesized by solvothermal reaction in the presence of phthalic acid under different solvents (DMF and DEF). Synthetic investigations and structural analyses reveal that the two pairs of MOFs show distinct frameworks with remarkable solvent-directed feature, although they were assembled from the same starting materials, i.e., CoCl2·6H2O with tricarboxylate-BTC for 1 and 2, or with expanded derivative BTB for 3 and 4. The CO2 adsorption properties of these MOFs were investigated and the results indicate that the activated MOF 1 presents the highest CO2 uptake capability of 85.8 cm3 g−1 at 1 atm and 273 K.