Inclusion in microporous β-bis(1,1,1-trifluoro-5,5-dimethyl-5-methoxyacetylacetonato)copper(II), an organic zeolite mimic

In this contribution, we show that the porous beta-form of the title complex preserves its host lattice pore structure in the presence of more than 100 guests. Among the species that are able to promote the alpha-to-beta transformation and that are capable of being included as guests are the gaseous and condensed hydrocarbons, their halo derivatives, alcohols, diols, aldehydes, ketones, ethers, esters, ethers of inorganic acids, acids, nitriles, and a variety of substituted aromatics. The empty beta-form behaves like a microporous sponge, instantly absorbing significant quantities even of highly volatile compounds such as methane, ethane, and propane. The material demonstrates zeolite-like behavior, not only from the robustness of the empty pore structure, but also from its propensity for efficient adsorption and desorption. The thermal stability of inclusions with normal paraffins increases from 142 degrees C (incongruent melting) to 163.5 degrees C (true melting) in the series from n-C5 to n-C16, while the guest-free alpha-form of the complex melts at 157 degrees C. The interaction of the complex with alcohols illustrates competing options between chemical bonding to copper and physical sorption into the microporous beta-form. Methanol and ethanol coordinate to copper, thereby taking part in building, respectively, 2-D and 1-D polymers, whereas higher alcohols induce conversion to a 3-D beta-form, stabilizing this porous modification by inclusion. From the observed stoichiometry and thermal stability, the host matrix is shown to be capable of molecular recognition of alcohols that have a shape and dimensions complementary to available pore geometry. Finally, the prospects for the rational design of new 3-D microporous polymers of bis-chelate building blocks are discussed.