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The introduction of enhanced functionalization is a key aspect in the current design of cage chemistry. At the moment, several approaches are intensively investigated. The synthesis of cage compounds that display endohedral functionalization plays a key role among them. Here, the studies of reactions that occur in endohedral‐functionalized cage compounds is reviewed. After an introduction in current trends in cage‐chemistry the discussion of reactions in endohedral‐cage compounds is divided into three sections. These are: 1) Endohedral groups that are by themselves functional, 2) endohedral groups that can bind to a transition‐metal complex and 3) endohedral groups that can bind by themselves to a metal. The article closes with an outlook on additional current developments in the field of endohedral‐functionalized cage‐compounds, which may contribute in the future towards reactivity in cage compounds. [ABSTRACT FROM AUTHOR]

Herein, we report a fabrication of well-naked palladium nanoparticles encapsulated within hollow porous carbon nanospheres (Pd@HPCNs) by carbonization of palladium-encapsulated hyper-crosslinking hollow porous polymeric nanospheres (Pd@HPPNs) with a silica-protection strategy. Owing to the classical yolk-shell structure, high surface area and permeable microporous carbon shell, the resultant Pd@HPCNs exhibited a highly size-selective catalysis performance toward oxidation of various alcohols via the molecular sieving. This method can be further developed into a general strategy to immobilize various metal or metal oxide into HPCNs nanoreactors as promising catalyst candidates for future practical applications. A novel fabrication of palladium-encapsulated in hollow porous carbon nanospheres for size-selective catalysis is reported for the first time. Image 1 • A synthesis of ligand-free palladium nanoparticles encapsulated in hollow porous carbon nanospheres was developed. • The resultant Pd@HPCNs exhibited a highly size-selective catalysis performance toward oxidation of various alcohols via the molecular sieving. • Such method could be a general approach to produce various metal-encapsulated hollow porous carbon nanospheres. [ABSTRACT FROM AUTHOR]

Heterogeneous catalysts with tunable micropores and confined metal sites in micropores are of great significance in size-selective catalysis but remain difficult to be achieved in organic polymers. In this work, we provide a micropore-confining strategy for the design of size-selective heterogeneous catalysts and investigate their size selectivity on various catalytic reactions. The palladium (Pd)@microporous tetrastyrene polymer (MTP) was synthesized via a Pd-catalyzed coupling reaction, where superfine Pd nanoparticles in situ form in the micropores of MTP. The results demonstrate that Pd@MTP catalysts not only exhibit greatly enhanced catalytic activity but also present excellent size selectivity on various catalytic systems. This research greatly expands the application scope of microporous organic polymers in size-selective heterogeneous catalysis. [ABSTRACT FROM AUTHOR]

In situ immobilization of enzyme into metal–organic frameworks (MOFs) is performed through a one-step and facile method. Candida antarctica lipase B (CalB) is directly embedded in zeolitic imidazolate framework (ZIF)-8 by simply mixing an aqueous solution of 2-methylimidazole and zinc nitrate hexahydrate [Zn(NO3)2⋅6H2O] containing CalB at room temperature. Due to the intrinsic micropores of ZIF-8, the obtained CalB@ZIF composite is successfully applied in size-selective transesterification reaction in organic solvent. CalB@ZIF not only shows much higher catalytic activity but also exhibits higher thermal stability than free CalB. Besides, the robust ZIF-8 shell also offers the hybrid composites excellent reusability.

The construction of 2D and 3D covalent organic frameworks (COFs) from functional moieties for desired properties has gained much attention. However, the influence of COFs dimensionality on their functionalities, which can further assist in COF design, has never been explored. Now, by selecting designed precursors and topology diagrams, 2D and 3D porphyrinic COFs (2D‐PdPor‐COF and 3D‐PdPor‐COF) are synthesized. By model building and Rietveld refinement of powder X‐ray diffraction, 2D‐PdPor‐COF crystallizes as 2D sheets while 3D‐PdPor‐COF adopts a five‐fold interpenetrated pts topology. Interestingly, compared with 2D‐PdPor‐COF, 3D‐PdPor‐COF showed interesting properties, including 1) higher CO2 adsorption capacity; 2) better photocatalytic performance; and 3) size‐selective photocatalysis. Based on this study, we believe that with the incorporation of functional moieties, the dimensionality of COFs can definitely influence their functionalities. [ABSTRACT FROM AUTHOR]

A synthetic strategy is reported here for the selective containment of oxide nanoparticles of base metals within zeolitic voids of molecular dimensions. The technique, though generally applicable, is specifically illustrated to encapsulate Ni, Co, and Fe oxides within LTA, MFI, and FAU zeolites through hydrothermal framework crystallization in the presence of ligand-protected metal cations. Such ligands contain bidentate amine groups that preclude the precipitation of metal precursors in alkaline synthesis gels, and alkoxysilane moieties that form covalent linkages with nucleating zeolite precursors to enforce metal uptake into crystallized solids. These ligands are removed by subsequent oxidative treatments that nucleate oxide nanoparticles without structural degradation of the zeolites. The clusters are small (<2.5 nm) and uniformly distributed in size, reflecting their constrained growth within zeolite crystals. In contrast with exchange strategies for encapsulation, which lead to grafted cations and dense metal aluminosilicates, these methods form oxide nanoparticles, evident from infrared spectra of samples exposed to CO. Oxide nanoparticles undergo more facile redox cycles than grafted cations or dense aluminosilicates, thus rendering oxide domains more effective oxidation catalysts. The dynamics and stoichiometry of nanoparticle reduction in H 2 confirmed the presence of NiO, Co 3 O 4 , and Fe 2 O 3 clusters and their more facile reducibility relative to metal aluminosilicates. Ethanol oxidation rates on these clusters were essentially unaffected by exposure to bulky thiol poisons that titrate metal oxide surfaces, reflecting the selective placement of the oxide nanoparticles within the confines of microporous voids, where they are protected from contact by large molecules. These synthetic strategies and guiding principles circumvent long-standing hurdles in the selective encapsulation of base metals, and provide enabling routes for the synthesis of the many metal-zeolite systems that confront similar hurdles. [ABSTRACT FROM AUTHOR]

Keywords: bioinorganic chemistry; confined space; organocatalysis; self-assembly; size-selective catalysis EN bioinorganic chemistry confined space organocatalysis self-assembly size-selective catalysis 1 1 1 05/11/23 20230508 NES 230508 B The Front Cover b illustrates the self-assembly of a cartoon parachute group conducting experiments. Bioinorganic chemistry, confined space, organocatalysis, self-assembly, size-selective catalysis Front Cover: Reactions in Endohedral Functionalized Cages (Eur. J. Org. [Extracted from the article]

By adjusting the addition time of palladium nanoparticles, during the formation of ZIF-8, an efficient and facile method was proposed to control the palladium spatial distribution within ZIF-8 crystals. Characterizations reveal that the addition time can significantly affect the particle size of Pd@ZIF-8 and palladium spatial distribution. As the PVP-stabilized palladium nanoparticles are added at the early stage of the ZIF-8 formation, larger ZIF-8 crystals with completely embedded palladium nanoparticles can be obtained. Introducing the PVP-stabilized palladium nanoparticles later can lead to the formation of smaller ZIF-8 crystals with all the palladium nanoparticles on the outer surfaces of ZIF-8. The catalytic performance of Pd@ZIF-8 strongly depends on the palladium spatial distribution, and the Pd@ZIF-8 with completely embedded palladium nanoparticles can provide excellent product selectivity and better catalytic stability in the hydrogenation of alkenes. [ABSTRACT FROM AUTHOR]

A new Pd@ZIF-L hybrid catalyst having a unique crosshair-star shape with a size of about 20 μm was synthesized, in which a two-dimensional layered zeolitic imidazolate framework-L (ZIF-L) was used as a support to immobilize palladium nanoparticles via an assembly method. The hybrid catalyst with unique cushion-shaped cavities between layers with a size of 6.64 Å can be used for the diffusion of specific reactants not achievable by other ZIF systems such as ZIF-8. The crystal structure and morphology of Pd@ZIF-L are strongly dependent on the synthesis conditions. Palladium nanoparticles with an average size of 3 nm are homogeneously encapsulated in the ZIF-L crystals. The as-synthesized Pd@ZIF-L catalyst favors the conversion of alkenes with larger molecular sizes, and exhibits excellent molecule-size-selectivity and anti-leaching performance. [ABSTRACT FROM AUTHOR]

Abstract: This work presents a new oxovanadium(IV)–cucurbit[6]uril complex, which combines the catalytic properties of the metal ion with the size-excluding properties of the macrocycle cavity. In this coordination compound, the ions are coordinated to the oxygen atoms located at the rim of the macrocycle in slightly distorted square-pyramidal configurations, which are in fact symmetries. This combination results in a size-selective heterogeneous catalyst, which is able to oxidize linear alkanes like n-pentane at room temperature, but not styrene, cyclohexane or z-cyclooctene, which are too big to enter the cucurbit[6]uril cavity. The results presented here contribute to understanding the mechanism of alkane catalytic oxidation by oxovanadium(IV) complexes. [ABSTRACT FROM AUTHOR]

Size-selective catalysis is of key importance in the conversion of crude oil or biomass. Here, we fabricate three pillar[5]arene-integrated porous organic polymers with three-dimensional (3D) network structures using 3D cross-linkers. The resulting polymers possess a high surface-to-mass ratio and exhibit exceptional size-selective catalysis in Knoevenagel condensation reactions. In addition, a mechanistic study indicates that the size-selective catalysis is due to the host-guest interaction between pillar[5]arene and substrates. This study suggests that macrocycle-containing polymers could be a promising candidate for size-selective catalysis.

The impact of dimensionality and flexibility on anticipated properties has prompted major research focus to three-dimensional covalent organic frameworks (3D COFs), where astute functionalization of porous channels for dynamic CO 2 adsorption as well as size-exclusive C-H activation under eco-friendly condition are the most intriguing advanced applications. Herein, we report an imine-based, diamondoid COF that embraces one-dimensional porous channels in spite of ninefold interpenetration. A combination of intrinsic microporosity and pore wall decoration with accessible N atoms from linear strut renders this 3D COF display reasonable CO 2 affinity with decent selectivity (CO 2 /N 2 : 64.2; CO 2 /CH 4 : 10.5) alongside worthy multicyclic CO 2 uptake-release recurrence. Interestingly, the COF undergoes solvent-assisted alteration to a pore-stretched structure via -C═N- "pedal" motion with a concomitant enhancement in CO 2 uptake, where steady reversibility of such structural dynamism instigates unprecedented CO 2 adsorption switch up to seven consecutive cycles. Integration of 2,2'-bipyridyl units benefits anchoring of homogeneous catalyst to device first-ever Ru(Bpy) 2 2+ hooked diamondoid COF (Ru-COF), which performs visible-light-triggered oxidative cyanation of tertiary amines at room temperature, using molecular oxygen as a selective oxidant in green solvent H 2 O. The photocatalyst-engineered COF manifests excellent recyclability and comparable activity to that of homogeneous catalyst. To the best of Ru-COF, atom-economic photocyanation is realized via in situ generated iminium ion, wherein larger-sized substrates exhibit insignificant conversion of α-aminonitriles and validate rarest size selectivity in oxidative Strecker reaction. This study not only demonstrates potential of 3D COF as next-generation dynamic CO 2 adsorbent but also sheds light on tailor-made fabrication of smart functional material for promising catalytic applications through an environmentally benign route.

In situ immobilization of enzyme into metal-organic frameworks (MOFs) is performed through a one-step and facile method. Candida antarctica lipase B (CalB) is directly embedded in zeolitic imidazolate framework (ZIF)-8 by simply mixing an aqueous solution of 2-methylimidazole and zinc nitrate hexahydrate [Zn(NO 3 ) 2 ⋅6H 2 O] containing CalB at room temperature. Due to the intrinsic micropores of ZIF-8, the obtained CalB@ZIF composite is successfully applied in size-selective transesterification reaction in organic solvent. CalB@ZIF not only shows much higher catalytic activity but also exhibits higher thermal stability than free CalB. Besides, the robust ZIF-8 shell also offers the hybrid composites excellent reusability., (Copyright © 2020 Wang, Zhang, Tan, Qi and Wu.)