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The chiral recognition ability of microporous MOF [{Cu12I(trz)8}·4 Cl·8 H2O]n in adsorption processes was studied. The MOF sample was obtained from achiral molecules in the absence of an external source of chirality. It has, in its structure, a right-handed single-stranded helix nanotube with a size of 14 Å and a left-handed single-stranded helix nanotube measuring 4.9 Å. The aim of this study was to use substances capable of adsorbing only in one type of nanotubes. This could lead to chiral recognition by racemic crystals. To test the recognition ability, the enantiomers of limonene were used. The limonene dimensions were too large to fit in the left-handed nanotube but small enough to get adsorbed by the right-handed nanotube. To analyze the enantioselectivity of [{Cu12I(trz)8}·4 Cl·8 H2O]n, inverse gas chromatography was used. The specific retention volumes were calculated and the adsorption isotherms were plotted. In addition, the MOF sample was characterized by XRD, IR spectrometry, and porosimetry analyses. It has been shown that the MOF-based stationary phase was capable of chiral recognition. The maximum selectivity coefficient was 1.43. The reliability of differences in enantiomer adsorption isotherms was confirmed by t-test. The data obtained proved the chiral recognition ability. During adsorption data collection, a decrease in enantioselectivity was observed. It was caused by the irreversible (under gas chromatography conditions) adsorption of the limonene enantiomers in the MOF pores. This fact was confirmed by eluting n-heptane through a MOF column after a gas chromatographic experiment. Furthermore, irreversible nitrogen adsorption was observed during the porosimetry experiment. [ABSTRACT FROM AUTHOR]

Zeotype borophosphates are porous adsorbents with a 3D open framework. The unique feature of borophosphates is noncentrosymmetric or even chiral structures. The chirality emerged as an asymmetrical arrangement of atoms in crystals and can be referred to the supramolecular, not molecular, chirality hierarchy level. In this work, the zeotype copper borophosphate LiCu 2 [BP 2 O 8 (OH) 2 ] was studied as a promising adsorbent for enantiomer separation. LiCu 2 [BP 2 O 8 (OH) 2 ] has a rare feature: without any external source of chirality, crystals with only [CD(-)284] and [CD(-)760] Cotton effects are synthesized. Tryptophan enantiomer adsorption on LiCu 2 [BP 2 O 8 (OH) 2 ] was studied. At almost all tryptophan concentrations, enantioselectivity was observed. At nonequilibrium conditions, enantioselectivity coefficients were higher than at adsorption equilibrium. In some cases, chiral recognition was not observed at equilibrium but occurred before equilibrium. In a nonequilibrium area of amount of adsorbed substance vs adsorption time curve, a phenomenon of very high enantioselectivity was discovered. The enantioselectivity coefficient values were 3-5, and even 11.8. Such extremely high enantioselectivity values were caused by the nontrivial kinetic curve for l-tryptophan. A far from the equilibrium, a plateau was observed on the curve. At the end of the plateau, the maximal enantioselectivity was observed. This mechanism of enantioselectivity enhancement can be useful for chromatographic separations, chemical sensors, and catalysts.