Self-assembly allows structures to organize themselves into regular patterns by using local forces to find the lowest-energy configuration. However, assembling organic and inorganic building blocks in an ordered framework remains challenging due to  difficulties in rationally interfacing two dissimilar materials. Herein, the ensemble of polyoxometalates (POMs) and cyclodextrins (CDs) as molecular building blocks (MBBs) has yielded two unprecedented POM-CD-MOFs, namely [PW12O40]3– and α-CD MOF (POT-CD) as well as [P10Pd15.5O50]19– and γ-CD MOF (POP-CD), with distinct properties not shared by their isolated parent MBBs. Markedly, the POT-CD features a nontraditional enhanced Li storage behavior by virtue of a unique “amorphization and pulverization” process. This opens the door to a new generation of hybrid materials with tuned structures and customized functionalities.

Noble metal catalysts, in particular palladium-containing materials, are of prime commercial interest, because of their role as oxidation catalysts in automobile emission-control systems and reforming catalysts for the production of high-octane gasoline. However, despite almost two centuries of research, the precise structure of such materials is still ill-defined on the sub-nanometer scale, which severely limits the understanding of the underlying catalytic mechanisms. As a burgeoning class of structurally well-defined noble metal oxide nanoclusters, polyoxopalladates (POPs) have been highly rated as ideal models to fully decipher the molecular mechanism of noble metal-based catalysis. Being at the frontier of polyoxometalates (POMs), the chemistry of POPs, which are based exclusively on Pd centers as addenda is currently progressing rapidly, owing to their structural and compositional novelty, high solution stability, combined with promising applications especially as noble metal-based catalysts. Controlled hydrolysis-condensation processes of square-planar PdO units in the presence of external oxyacid heterogroups (e.g., AsO, PO, and SeO) drive the self-assembly of such discrete, polynuclear Pd-oxo nanoclusters in facile one-pot reactions using aqueous solvents. By now, more than 70 POPs have been discovered, encompassing a large structural variety, including cube, star, bowl, dumbbell, wheel, and open-shell archetypes. Moreover, the POP cages can serve as adaptable molecular containers for encapsulation/interaction with a range of metallic elements across the s, p, d, and f blocks of the periodic table, resulting in a library of host-guest assemblies of varying shapes and sizes. Besides a delicate balance of experimental variables, the fine-tuning of POP structure, composition, and properties is possible by systematic replacement of the metal ion guest and/or the capping heterogroups. Besides, nearly all POPs obtained so far could be perfectly rationalized by theoretical calculations, and even prediction of the design and synthesis of new POP structures is possible. The excellent stability of POPs in the solid state and in solution (both aqueous and organic media) and gas phase allows for applications mainly in homo- and heterogeneous catalysis or as molecular precursors for monodisperse nanoparticles via an ingenious bottom-up route for functional nanotechnology. Apart from catalysis, owing to the unique structural features of POPs, other areas of interest exist, for example, in magnetism as molecular spin qubits and in biology as aqueous-phase macromolecular models. Overall, as a distinct subclass of POMs, POPs not only integrate the advantages of tunable shape, size, composition, solution stability, redox activity, and facile synthetic procedures, but drive immense potential for achieving an atom-to-atom fabrication and modulation of nanostructures as well, thereby providing models for unveiling mechanistic insight of noble metal-based catalysis at the molecular level, which will, in turn, guide the progra...

Complexes made by hosts that completely surround their guests provide a means to stabilize reactive chemical intermediates, transfer biologically active cargo to a diseased cell, and construct molecular-scale devices. By the virtue of inorganic host-guest self-assembly, nucleation processes in the cavity of a {P W }-archetype phosphotungstate has afforded a nanoscale 16-Al -32-oxo cluster and its Ga analogue that contain the largest number of Al /Ga ions yet found in polyoxometalate (POM) chemistry. Interestingly, the rich Lewis acid Al centers within the Lewis base POM support shows an exceptional proton conductivity of 4.5×10 S cm (85 °C, 70 % RH; RH: relative humidity), which is by far the highest conductivity reported among POM-based single-crystal proton conductors.

The three novel, discrete palladium(II)-oxo clusters [CaPd12O8(PhAsO3)8](6-) (CaPd12), [SrPd12O6(OH)3(PhAsO3)6(OAc)3](4-) (SrPd12), and [BaPd15O10(PhAsO3)10](8-) (BaPd15) encapsulating alkaline earth metal ions were prepared and fully characterized by a multitude of solution and solid-state physicochemical techniques. We have discovered a structure-directing template effect induced by the respective size of the alkaline earth guest ion, which determines the detailed condensation arrangement of the peripheral Pd(II)-oxo shell. The unprecedented SrPd12 with an open-shell type structure is of particular importance and reflects a successful strategy for deliberate design of new structural classes of polyoxo-noble-metalates. Furthermore, the unusual acetate-water ligand exchange phenomenon renders SrPd12 as a promising candidate for noble-metal-based catalysis.

The separation of benzene derivatives is energy intensive and laborious as a result of the overlapping physicochemical properties of these isomers. Here, we report on the separation of ortho-disubstituted benzene isomers using cucurbit[7]uril (CB7) aqueous solution with more than 92% selectivity. Thermodynamic and kinetic analysis proves that the ortho-isomer has stronger binding ability and slower decomplexation rate constant than the para-and metaisomers when hosted by CB7. Optimized host-guest models indicate that the ortho-isomer with the smallest aspect ratio well matches the spherical interior cavity of CB7, resulting in highly stable complexes. Furthermore, laboratory scale-up experiments using commercial xylenes and C8 aromatic fraction of pyrolysis gasoline proved that CB7 is able to separate ortho-xylene (OX) with a remarkable selectivity of up to 83%. We believe that this work accentuates the role of molecular recognition studies using macrocyclic hosts to improve the quality and energy bill of critical industrial separations.