Tuning the supramolecular isomerism of MOF-74 by controlling the synthesis conditions

Abstract

Controlled synthesis of MOF materials with specific properties is highly relevant for practical applications and it still remains a challenging task. This work highlights the key role played by the solvents and specific modulators in the formation and stability of two isomers of the well-known MOF-74.

Synthesis of Chiral MOF‐74 Frameworks by Post‐Synthetic Modification by Using an Amino Acid

“…[52] Our group reported the synthesis of MOF-74 in the presence of bulky chiral alkaloids leadingt oanews tructuralt opology, HIMS-74, whichi sb uilt from binuclear secondary building units. [46] We attributed the formation of the binuclear SBUs to the N,O-coordination of the alkaloids to the Zn 2 + ions during the nucleation process, thereby inhibiting the formation of the chain-like SBUs, which are characteristico ft he MOF-74 topology.I ns ubsequent studies, we replaced the bulky chiral alkaloids with the smallerp roline molecule. Our hypothesis was that, unlike the reactions performed by using chiral alkaloids, the use of d-o rl-Pro duringt he synthesis of MOF-74 would lead to chiral materials because of the reduced size of the additive.…”

“…[40][41][42][43] Furthermore, the quality of the VCD spectroscopic data is highly related to the sample homogeneity, [58] therefore our studies focused on post-modified materials synthesised using aZ n-MOF-74, which is highly homogeneous and has crystals with narrow size distribution. [46] The samples prepared in DMF show strong VCD signals in the region 1300-1700 cm À1 assignedt ot he coordinatedp roline molecules. The signala t1 609 cm À1 correlates very well with the IR band at 1600 cm À1 .T his band is assigned to the asymmetrics tretching of the carboxylate group of proline ( Figure 6).…”

“…[38][39][40][41][42][43][44][45] It has a3 Dh oneycomblike framework with 1D channels of ca. 11 , [46] built from organic linkers on the edges and ZnO 6 at the corners. The ZnO 6 octahedra form infinite helicalc hains via double oxygen bridges alongt he c axis, but of opposite handedness with P and M helical rods with a ratio P/M of 1:1 ( Figure 1).…”

“…In recent work, we showed that by using chiral cinchonaa lkaloids during the crystallisation of Zn-MOF-74 does not influence the P/M ratio or induce chirality.T he bulkiness of the chiral molecule and its weakc oordination to the metal ions afforded achiral structural isomers with discrete secondary buildingu nits (SBUs). [46] Consequently, we turn our attention to chiral inductors which are smaller and would easily be accommodated in the channels of Zn-MOF-74, for example, the chiral amino acid l-o rd-proline (l-o rd-Pro). Here, we discuss the synthesis and characterisation of the chiral materials obtained by using chiral induction with l-o r d-Pro.…”

CO2 sensing under ambient conditions using metal–organic frameworks

“…34) and HIMS-74. 35 Although Zn-UTSA-74 has the same number of open metal sites per secondary building unit (SBU) as Zn-MOF-74, a smaller CO 2 uptake is observed for UTSA-74 as compared to MOF-74. 34 The available open sites in HIMS-74 indicate that there are two adsorption sites per SBU, similar to those in UTSA-74, and therefore they show similar CO 2 uptakes.…”