Bioinspired Framework Catalysts: From Enzyme Immobilization to Biomimetic Catalysis

Enzymatic catalysis has fueled considerable interest from chemists due to its high efficiency and selectivity. However, the structural complexity and vulnerability hamper the application potentials of enzymes. Driven by the practical demand for chemical conversion, there is a long-sought quest for bioinspired catalysts reproducing and even surpassing the functions of natural enzymes. As nanoporous materials with high surface areas and crystallinity, metal-organic frameworks (MOFs) represent an exquisite case of how natural enzymes and their active sites are integrated into porous solids, affording bioinspired heterogeneous catalysts with superior stability and customizable structures. In this review, we comprehensively summarize the advances of bioinspired MOFs for catalysis, discuss the design principle of various MOF-based catalysts, such as MOF-enzyme composites and MOFs embedded with active sites, and explore the utility of these catalysts in different reactions. The advantages of MOFs as enzyme mimetics are also highlighted, including confinement, templating effects, and functionality, in comparison with homogeneous supramolecular catalysts. A perspective is provided to discuss potential solutions addressing current challenges in MOF catalysis.

Halogen-bonded architectures of multivalent calix[4]arenes

A 2D halogen bonded network of calixarene macrocycles was obtained by co-crystallization of a 1,3-alternate calix[4]arene as a tetravalent XB donor with a bidentate XB acceptor.

Coordination polymers with embedded recognition sites: lessons from cyclotriveratrylene-type ligands

Coordination polymers with molecular recognition sites are assembled using cyclotriveratrylene ligands. Many show differential guest-spaces with host and lattice sites available, however common host–guest and self-inclusion motifs can block sites.

Higher Analogues of Resorcinarenes and Pyrogallolarenes: Bricks for Supramolecular Chemistry

Easy scalable and eco-friendly syntheses of resorcin[5]arene, pyrogallol[5]arene, (2-nitro)resorcin[5]arene, (2-carboxyl)resorcin[5]arene, and resorcin[7]arene are presented and a wide range of upper-rim modifications is demonstrated. The macrocycles open the door toward expanding the rich covalent and supramolecular chemistry of [4]arenes with analogues having unique 5-fold and 7-fold symmetry.

Supramolecular-Macrocycle-Based Crystalline Organic Materials

Supramolecular macrocycles are well known as guest receptors in supramolecular chemistry, especially host-guest chemistry. In addition to their wide applications in host-guest chemistry and related areas, macrocycles have also been employed to construct crystalline organic materials (COMs) owing to their particular structures that combine both rigidity and adaptivity. There are two main types of supramolecular-macrocycle-based COMs: those constructed from macrocycles themselves and those prepared from macrocycles with other organic linkers. This review summarizes recent developments in supramolecular-macrocycle-based COMs, which are categorized by various types of macrocycles, including cyclodextrins, calixarenes, resorcinarenes, pyrogalloarenes, cucurbiturils, pillararenes, and others. Effort is made to focus on the structures of supramolecular-macrocycle-based COMs and their structure-function relationships. In addition, the application of supramolecular-macrocycle-based COMs in gas storage or separation, molecular separation, solid-state electrolytes, proton conduction, iodine capture, water or environmental treatment, etc., are also presented. Finally, perspectives and future challenges in the field of supramolecular-macrocycle-based COMs are discussed.

Solvent-responsive cavitand lanthanum complex

A new, solvent responsive tetra-phosphonate cavitand lanthanum complex forms a dimer in acetonitrile, interconverts into a monomeric complex in acetone and is disassembled in methanol.

2D networks of metallo-capsules and other coordination polymers from a hexapodal ligand

2D M₃L₂ coordination polymers (M = Re(i), Cu(ii), Co(ii), Ni(ii)) feature metal-linked M₆L₂-cages, and the Re(i) material absorbs iodine.

Molecular tectonics: high dimensional coordination networks based on methylenecarboxylate-appended tetramercaptothiacalix[4]arene in the 1,3-alternate conformation

Tetrasubstituted methylenecarboxylic-appended tetra-mercaptotetrathiacalix[4]arene (TMTCA), combined with transition metals, lead to high-dimensional coordination polymers.

Synthesis of para- and meta-imino- or -amino-methyl pyridyl-appended p-tert-butyl-calix[4]arene or p-tert-butyl-thiacalix[4]arene in 1,3-alternate conformation

The multistep synthesis of eight new ligands based on calix[4]arene or thiacalix[4]arene backbones blocked in a 1,3-alternate conformation and bearing four pyridyl units is presented.

Exploring biphenyl-2,4,4′-tricarboxylic acid as a flexible building block for the hydrothermal self-assembly of diverse metal–organic and supramolecular networks

This contribution reports the hydrothermal self-assembly synthesis, characterization, thermal stability, structural and topological features, and luminescence or magnetic properties of a new series of nine coordination compounds.

Copper coordination polymers from cavitand ligands: hierarchical spaces from cage and capsule motifs, and other topologies

Copper coordination polymers from cavitand ligands are reported including networked cage-motif structures, one of which takes up C₆₀ from solution.

The cyclotriveratrylene-type ligands (±)-tris(iso-nicotinoyl)cyclotriguaiacylene L1 (±)-tris(4-pyridylmethyl)cyclotriguaiacylene L2 and (±)-tris{4-(4-pyridyl)benzyl}cyclotriguaiacylene L3 all feature 4-pyridyl donor groups and all form coordination polymers with Cu^I and/or Cu^II cations that show a remarkable range of framework topologies and structures. Complex [Cu^I₄Cu^II_1.5(L1)₃(CN)₆]·CN·n(DMF) 1 features a novel 3,4-connected framework of cyano-linked hexagonal metallo-cages. In complexes [Cu₃(L2)₄(H₂O)₃]·6(OTf)·n(DMSO) 2 and [Cu₂(L3)₂Br₂(H₂O)(DMSO)]·2Br·n(DMSO) 3 capsule-like metallo-cryptophane motifs are formed which linked through their metal vertices into a hexagonal 2D network of (4³.12³)(4².12²) topology or a coordination chain. Complex [Cu₂(L1)₂(OTf)₂(NMP)₂(H₂O)₂]·2(OTf)·2NMP 4 has an interpenetrating 2D 3,4-connected framework of (4.6².8)(6².8)(4.6².8²) topology with tubular channels. Complex [Cu(L1)(NCMe)]·BF₄·2(CH₃CN)·H₂O 5 features a 2D network of 6³ topology while the Cu^II analogue [Cu₂(L1)₂(NMP)(H₂O)]·4BF₄·12NMP·1.5H₂O 6 has an interpenetrating (10,3)-b type structure and complex [Cu₂(L2)₂Br₃(DMSO)]·Br·n(DMSO) 7 has a 2D network of 4.8² topology. Strategies for formation of coordination polymers with hierarchical spaces emerge in this work and complex 2 is shown to absorb fullerene-C₆₀ through soaking the crystals in a toluene solution.

Highly selective adsorption and separation of aniline/phenol from aqueous solutions by microporous MIL-53(Al): a combined experimental and computational study

Experimental measurements have been combined with molecular simulations to investigate the adsorption and separation of aniline/phenol mixtures from aqueous solutions by the aluminum terephthalate MIL-53. The results show that the framework flexibility of this material plays a crucial role in the adsorption process and thus can greatly enhance the separation of the aniline/phenol mixture from their solutions. Compared with the conventional adsorbents, MIL-53(Al) shows the best performance for such systems of interest, from the points of view of both the adsorption capacities and the selectivities for aniline. The findings obtained in this work may facilitate more investigations in connection with the application of flexible nanoporous materials for the separation of organic compounds from liquid-phase environments.

A ladder-type coordination polymer constructed from two macrocyclic units – calix[4]arene tetracarboxylate and azamacrocyclic nickel(ii) complex

Spatially-separated polar channels and non-polar voids were shown to coexist in the crystal of a new type of coordination polymer formed by a hexaazamacrocyclic nickel(ii) cation and a lower rim substituted calix[4]arene tetracarboxylate trianion.

Molecular tectonics: generation of grid and porous diamondoid coordination networks by calixarene based tectons

Combinations of tetrakis meta-pyridyl appended tetrathia- or tetrathiamercapto-calix[4]arene in 1,3-A conformation with MX₂ (M = Cd, Co or Fe, X = Cl or Br), behaving as a neutral metallatecton, lead to 2D grid type and 3D porous diamondoid coordination networks.