Homochiral Porous Metal–Organic Polyhedra with Multiple Kinds of Vertices

Abstract

Metal−organic polyhedra featuring non-Archimedean/Platonic architectures with multiple kinds of vertices have aroused great attention for their fascinating structures and properties but are yet challenging to achieve. Here, we report a combinatorial strategy to make such nonclassic polyhedral cages by combining kinetically labile metal ions with non-planar organic linkers instead of the usual only inert metal centers and planar ligands. This facilitates the synthesis of an enantiopure twisted tetra(3-pyridyl)-based TADDOL (TADDOL = tetraaryl-1,3dioxolane-4,5-dimethanol) ligand (L) capable of binding Ni(II) ions to produce a regular convex cage, Ni 6 L 8 , with two mixed metal/organic vertices and three rarely reported concave cages Ni 14 L 8 , Ni 18 L 12 , and Ni 24 L 16 with three or four mixed vertices. Each of the cages has an amphiphilic cavity decorated with chiral dihydroxyl functionalities and packs into a three-dimensional structure. The enantioselective adsorption and separation performances of the cages are strongly dependent on their pore structure features. Particularly, Ni 14 L 8 and Ni 18 L 12 with wide openings can be solid adsorbents for the adsorptive and solid-phase extractive separation of a variety of racemic spirodiols with up to 98% ee, whereas Ni 6 L 8 and Ni 24 L 16 with smaller pore apertures cannot adsorb the racemates. The combination of single-crystal X-ray diffraction analysis of the host−guest adduct and GCMC simulation indicates that the enantiospecific recognition capabilities originate from the well-organized chiral inner sphere as well as multiple interactions within the chiral microenvironment. This work therefore provides an attractive strategy for the rational design of polyhedral cages, showing geometrically fascinating structures with properties different from those of classic assemblies.

Cofacial porphyrin organic cages. Metals regulating excitation electron transfer and CO2 reduction electrocatalytic properties

“…The great development of molecular cages, which are termed as void molecular structures with conned nano-sized cavities, has been witnessed in the eld of supramolecular chemistry, spanning from initial synthetic chemistry to interdisciplinary applications covering supramolecular chemistry and materials science. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] Their categories are diversied due to the various construction processes based mainly on coordination interactions, [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] covalent bonds, [35][36][37][38][39][40][41][42][43][44][45] and hydrogen bonds. [46][47][48]…”

“…The great development of molecular cages, which are termed as void molecular structures with confined nano-sized cavities, has been witnessed in the field of supramolecular chemistry, spanning from initial synthetic chemistry to interdisciplinary applications covering supramolecular chemistry and materials science. 1–16 Their categories are diversified due to the various construction processes based mainly on coordination interactions, 17–34 covalent bonds, 35–45 and hydrogen bonds. 46–50 Since 2009, porous organic cages (POCs) have emerged as a new class of functional organic materials with unique porous architectures through crystal engineering of dynamic covalent-bonded molecular cages.…”

Incorporation of Chiral Frustrated Lewis Pair into Metal–Organic Framework with Tailored Microenvironment for Heterogeneous Enantio- and Chemoselective Hydrogenation

“…Metal–organic frameworks (MOFs) have recently been extensively explored as a new class of heterogeneous catalyst; − their tunable structures and tailorable pore environments , also provide new opportunities for selective catalysis. − Although rapid development has been witnessed in the construction of chiral MOFs for enantioselective catalysis, − the combination of enantioselectivity with other selectivity (chemoselectivity) is still elusive, particularly for some important reactions in industry like hydrogenation. To realize heterogeneous enantio- and chemoselective hydrogenation, as inspired by enzymes, we propose to create an enzyme-mimic region (EMR) within the nanospace of a MOF (EMR@MOF) by grafting a chiral frustrated Lewis pair (CFLP) onto the MOF pore wall and tailoring the vicinity of CFLP with some auxiliary sites (ASs) (Scheme ); the chirality nature of CFLP can impart enantioselectivity, and the ASs may regulate chemoselectivity via preferable binding of certain bonds in the substrate reminiscent of enzymes.…”

Dynamic Interconversion and Induced-Fit Guest Binding with Two Macrocycle-Based Coordination Cages

“…Biological receptors, such as enzymes, often undergo conformation changes to fit target substrates. , Numerous artificial hosts, such as metallocycles and cages, have been constructed via coordination-driven self-assembly to imitate the property and functions of enzymes. − However, most coordination cages prepared to date are highly symmetrical and rigid. Recently, stimuli-responsive coordination cages with adaptive confined cavities, − which are built from flexible ligands or ligands with reduced symmetry, − are attracting increasing attention due to their great potential applications in allosteric guest binding and catalysis. − …”