(727b) Impact of Alkyl-Functionalized BTC On Properties of Copper-Based Metal-Organic Frameworks

Highly porous metal-organic frameworks [Cu₃(MBTC)₂(H₂O)₃]_n (where MBTC is methyl-1,3,5-benzenetricarboxylate) and [Cu₃(EBTC)₂(H₂O)₃]_n (where EBTC is ethyl-1,3,5-benzenetricarboxylate) have been solvothermally synthesized. The MOFs are isostructural to each other but do not form the same framework as HKUST-1 (CuBTC) due to the steric impact of the alkyl-functionalized ligands. The new MOFs are formed by two different [Cu₂(O₂CR)₄] units (where R is an aromatic ring), which create the three-dimensional framework with open metal sites and high surface areas. The pore size and adsorption properties are altered by introducing the organic groups methyl (-CH₃) or ethyl (-C₂H₅) groups. Compared with HKUST-1, these MOFs adsorb comparable amounts of carbon dioxide and methane at pressures up to 5 bar. However, water adsorption is significantly lower compared to HKUST-1 due to the hydrophobic functional groups. This work indicates that the strong adsorption preference of water on open metal sites can be negated with proper choice of hydrophobic functional group, without losing the strong interaction with other gases.