Synthesis of a Chiral Crystal Form of MOF-5, CMOF-5, by Chiral Induction

Chiral variants of the prototypal
metal–organic framework
MOF-5, Λ-CMOF-5 and Δ-CMOF-5, have been synthesized by
preparing MOF-5 in the presence of l-proline or d-proline, respectively. CMOF-5 crystallizes in chiral space group P213 instead of Fm3̅m as exhibited by MOF-5. The phase purity of CMOF-5 was
validated by single-crystal and powder X-ray diffraction, infrared
spectroscopy, thermogravimetric analysis, N2 adsorption,
microanalysis, and solid-state vibrational circular dichroism. CMOF-5
undergoes a reversible single crystal-to-single crystal phase change
to MOF-5 when immersed in a variety of organic solvents, although N-methyl-2-pyrrolidone (NMP) does not induce loss of chirality.
Indeed, MOF-5 undergoes chiral induction when immersed in NMP, affording
racemic CMOF-5.