Engineering Homochiral Metal–Organic Frameworks by Spatially Separating 1D Chiral Metal–Peptide Ladders: Tuning the Pore Size for Enantioselective Adsorption

Abstract

The reaction of the chiral dipeptide glycyl‐L(S)‐glutamate with CoII ions produces chiral ladders that can be used as rigid 1D building units. Spatial separation of these building units with linkers of different lengths allows the engineering of homochiral porous MOFs with enhanced pore sizes, pore volumes, and surface areas. This strategy enables the synthesis of a family of isoreticular MOFs, in which the pore size dictates the enantioselective adsorption of chiral molecules (in terms of their size and enantiomeric excess).

Biologically derived metal organic frameworks

“…However, robust and highly porous MOFs based on these ligands are scarce in the literature. [56], [65][66][67] (e.g alcohols) or non-polar (e.g alkyl chains) side chain, which is important for the formation of protein structures. Their rich coordination chemistry (through the carboxylate, amino groups and side chains) makes them as an attractive class of organic ligands for the formation of extended MOF structures.…”

“…[102] Changing the metal to Co II affords a configuration where the Co II ions are positioned at the vertices of the Co-L-GlyGlu ladders ( Table 2, entry 3). [65] The ladders are strongly connected via hydrogen bonds involving the amino group and carboxylate of GlyGlu in the neighboring ladders. [65] Along the c-axis, the ladders are also hydrogen bonded through a coordinated H2O molecules to the carboxylate group of an adjacent ladder.…”

“…[65] The ladders are strongly connected via hydrogen bonds involving the amino group and carboxylate of GlyGlu in the neighboring ladders. [65] Along the c-axis, the ladders are also hydrogen bonded through a coordinated H2O molecules to the carboxylate group of an adjacent ladder. [65] Peptide derived bio-MOFs constructed from networks made from dipeptides such as [Zn (GlyThr) 2] results in the generation of 1-dimensional channels, however in the former bio-MOF, the presence of Thr leads in the formation of strong interactions with the adjacent layer, reinforcing the stability in the 3-dimensional crystal structure.…”

“…[65] Along the c-axis, the ladders are also hydrogen bonded through a coordinated H2O molecules to the carboxylate group of an adjacent ladder. [65] Peptide derived bio-MOFs constructed from networks made from dipeptides such as [Zn (GlyThr) 2] results in the generation of 1-dimensional channels, however in the former bio-MOF, the presence of Thr leads in the formation of strong interactions with the adjacent layer, reinforcing the stability in the 3-dimensional crystal structure. [106] For the latter [Zn(GlyAla)2], the pores collapse upon desolvation but they can be recovered when polar molecules diffuse into its pores.…”

“…The use of a peptide with two carboxylate and one amino functions, glycyl-L(S)-glutamate (LGlyGlu) with Co II , leads in the construction of a chiral and rigid ladder (Co-L-GlyGlu) that was used in reticular synthesis to link the ladders and induce porosity (please see section 3.2 for structural description) ( Figure 5). [65] Replacing the coordinated terminal H2O molecules with pillar ligands with different length such as bipy (Co-LGlyGlubipy), azobipy (Co-L-GlyGluazobipy), azinebipy (Co-LGlyGluazinebipy) or bpeb (Co-L-GlyGlubpeb) afforded BET surface areas of 261 m 2 /g, 299 m 2 /g , 315 m 2 /g, and 601 m 2 /g, respectively, allowing for the assembly of porous homochiral MOFs from an originally non-porous structure. [65] The Co-L-GlyGlu units and their stacking are not affected by this process and subsequently the size of the pores is defined by the length of the pillar ligand used.…”