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Macroscopic electric motors continue to have a large impact on almost every aspect of modern society. Consequently, the effort towards developing molecular motors1–3 that can be driven by electricity could not be more timely. Here we describe an electric molecular motor based on a [3]catenane4,5, in which two cyclobis(paraquat-p-phenylene)6 (CBPQT4+) rings are powered by electricity in solution to circumrotate unidirectionally around a 50-membered loop. The constitution of the loop ensures that both rings undergo highly (85%) unidirectional movement under the guidance of a flashing energy ratchet7,8, whereas the interactions between the two rings give rise to a two-dimensional potential energy surface (PES) similar to that shown by FOF1 ATP synthase9. The unidirectionality is powered by an oscillating10 voltage11,12 or external modulation of the redox potential13. Initially, we focused our attention on the homologous [2]catenane, only to find that the kinetic asymmetry was insufficient to support unidirectional movement of the sole ring. Accordingly, we incorporated a second CBPQT4+ ring to provide further symmetry breaking by interactions between the two mobile rings. This demonstration of electrically driven continual circumrotatory motion of two rings around a loop in a [3]catenane is free from the production of waste products and represents an important step towards surface-bound14 electric molecular motors.

Complexation between a viologen radical cation (V.+ ) and cyclobis(paraquat-p-phenylene) diradical dication (CBPQT2(.+) ) has been investigated and utilized extensively in the construction of mechanically interlocked molecules (MIMs) and artificial molecular machines (AMMs). The selective recognition of a pair of V.+ using radical-pairing interactions, however, remains a formidable challenge. Herein, we report the efficient encapsulation of two methyl viologen radical cations (MV.+ ) in a size-matched bisradical dicationic host - namely, cyclobis(paraquat-2,6-naphthalene)2(.+) , i.e., CBPQN2(.+) . Central to this dual recognition process was the choice of 2,6-bismethylenenaphthalene linkers for incorporation into the bisradical dicationic host. They provide the space between the two bipyridinium radical cations in CBPQN2(.+) suitable for binding two MV.+ with relatively short (3.05-3.25 A) radical-pairing distances. The size-matched bisradical dicationic host was found to exhibit highly selective and cooperative association with the two MV.+ in MeCN at room temperature. The formation of the tetrakisradical tetracationic inclusion complex - namely, [(MV)2 ⊂CBPQN]4(.+) - in MeCN was confirmed by VT 1 H NMR, as well as by EPR spectroscopy. The solid-state superstructure of [(MV)2 ⊂CBPQN]4(.+) reveals an uneven distribution of the binding distances (3.05, 3.24, 3.05 A) between the three different V.+ , suggesting that localization of the radical-pairing interactions has a strong influence on the packing of the two MV.+ inside the bisradical dicationic host. Our findings constitute a rare example of binding two radical guests with high affinity and cooperativity using host-guest radical-pairing interactions. Moreover, they open up possibilities of harnessing the tetrakisradical tetracationic inclusion complex as a new, orthogonal and redox-switchable recognition motif for the construction of MIMs and AMMs.

Summary Mechanically interlocked molecules (MIMs) that undergo controllable internal motions of their component parts in more than one dimension are rare entities in the molecular world. Cyclic [2]daisy chains ([c2]DCs) are a class of MIMs that have been identified as prototypes for molecular muscles. It remains, however, a challenge to synthesize [cn]DCs with n > 2 selectively and efficiently. Herein, we report the design and synthesis of [c3]DCs employing radical and anionic templates. Two mechanically interlocked [c3]DCs with 18 positive charges were obtained in >90% yields. One [c3]DC displayed good air stability in its radical cationic form, while the other underwent reversible “co-conformational” switching between open macrocyclic and closed trisarm-shaped forms under electrochemical control. These findings provide not only two-dimensional MIMs with attractive electronic and switchable properties, but also a starting point for the design of extended molecular arrays, which could become the forerunners of adjustable molecular nets and breathable molecular membranes.

Suitanes are a class of mechanically interlocked molecules (MIMs) that consist of two components: a body with limbs protruding outward and a suit that fits appropriately around it, so that there is no easy way for the suit to be removed from the body. Herein, we report the synthesis and characterization of a suit[3]ane, which contains a benzotrithiophene derivative (THBTT) with three protruding hexyl chains as the body and a 3-fold symmetric, extended pyridinium-based cage, namely, HexaCage6+, as the suit. Central to its realization is effective templation, provided by THBTT during cage formation, an observation that has been supported by the strong binding constant between benzotrithiophene (BTT) and the empty cage. The solid-state structure of the suit[3]ane reveals that the body is confined within the suit's cavity with its alkyl chains protruding outward through the orifices in the cage. Notably, such a seemingly unstable molecule, having three flexible alkyl chains as its only protruding limbs, does not dissociate after prolonged heating in CD3CN at 100 °C under pressure for 7 days. No evidence for guest exchange with the host was observed at this temperature in a 2:1 mixture of THBTT and HexaCage6+ in CD3CN. The results indicate that flexible protruding limbs are sufficient for a suit[3]ane to remain mechanically stable even at high temperatures in solution.

The assembly of a kinetically trapped daisy chain polymer under redox control has been achieved with a self-complementary monomer using an energy ratchet mechanism. The monomer is composed of a molecular pump at one end and a cyclobis(paraquat

The efficient preparation of single-crystalline ionic polymers and fundamental understanding of their structure-property relationships at the molecular level remains a challenge in chemistry and materials science. Here, we describe the single-crystal structure of a highly ordered polycationic polymer (polyelectrolyte) and its proton conductivity. The polyelectrolyte single crystals can be prepared on a gram-scale in quantitative yield, by taking advantage of an ultraviolet/sunlight-induced topochemical polymerization, from a tricationic monomer-a self-complementary building block possessing a preorganized conformation. A single-crystal-to-single-crystal photopolymerization was revealed unambiguously by in situ single-crystal X-ray diffraction analysis, which was also employed to follow the progression of molecular structure from the monomer, to a partially polymerized intermediate, and, finally, to the polymer itself. Collinear polymer chains are held together tightly by multiple Coulombic interactions involving counterions to form two-dimensional lamellar sheets (1 nm in height) with sub-nanometer pores (5 Å). The polymer is extremely stable under 254 nm light irradiation and high temperature (above 500 K). The extraordinary mechanical strength and environmental stability-in combination with its impressive proton conductivity (∼3 × 10

Summary For neutral intramolecular circuits with two constitutionally identical branches, a maximum 4-fold increase in total conductance can be obtained according to constructive quantum interference (CQI). For charged intramolecular circuits, however, the strong electrostatic interactions entangle the quantum states of these two parallel pathways, thus introducing complicated transport behavior that warrants experimental investigation of the intramolecular circuit rules. Here, we report that a tetracationic cyclophane with parallel channels exhibits a 50-fold conductance enhancement compared with that of a single-channel control, an observation that supplements intramolecular circuit law in systems with strong Coulombic interactions. Flicker noise measurements and theoretical calculations show that strong electrostatic interactions between charged parallel channels—serving as the chemical gate to promote the effective conductance of each channel—and CQI boosts the total conductance of the two-channel circuit. The molecular design presented herein constitutes a proof-of-principle approach to charged intramolecular circuits that are desirable for quantum circuits and devices.

A class of γ-cyclodextrin-containing hybrid frameworks (CD-HFs) has been synthesized, employing γ-cyclodextrin (γ-CD) as the primary building blocks, along with 4-methoxysalicylate (4-MS-) anions as the secondary building blocks. CD-HFs are constructed through the synergistic exploitation of coordinative, electrostatic, and dispersive forces. The syntheses have been carried out using an organic counteranion co-assembly strategy, which allows for the introduction of 4-MS-, in place of inorganic OH-, into the cationic γ-CD-containing metal-organic frameworks (CD-MOFs). Although the packing arrangement of the γ-CD tori in the solid-state superstructure of CD-HFs is identical to that of the previously reported CD-MOFs, CD-HFs crystallize with lower symmetry and in the cuboid space group P43212-when compared to CD-MOF-1, which has the cubic unit cell of I432 space group-on account of the chiral packing of the 4-MS- anions in the CD-HF superstructures. Importantly, CD-HFs have ultramicroporous apertures associated with the pore channels, a significant deviation from CD-MOF-1, as a consequence of the contribution from the 4-MS- anions, which serve as supramolecular baffles. In gas adsorption-desorption experiments, CD-HF-1 exhibits a Brunauer-Emmett-Teller (BET) surface area of 306 m2 g-1 for CO2 at 195 K, yet does not uptake N2 at 77 K, confirming the difference in porosity between CD-HF-1 and CD-MOF-1. Furthermore, the 4-MS- anions in CD-HF-1 can be exchanged with OH- anions, leading to an irreversible single-crystal to single-crystal transformation, with rearrangement of coordinated metal ions. Reversible transformations were also observed in CD-MOF-1 when OH- ions were exchanged for 4-MS- anions, with the space group changing from I432 to R32. This organic counteranion co-assembly strategy opens up new routes for the construction of hybrid frameworks, which are inaccessible by existing de novo MOF assembly methodologies.

Although host–guest pairing interactions between bisradical dicationic cyclobis(paraquat-p-phenylene) (BB2(˙+)) and the bipyridinium radical cation (BIPY˙+) have been studied extensively, host molecules other than BB2(˙+) are few and far between., Although host–guest pairing interactions between bisradical dicationic cyclobis(paraquat-p-phenylene) (BB2(˙+)) and the bipyridinium radical cation (BIPY˙+) have been studied extensively, host molecules other than BB2(˙+) are few and far between. Herein, four bisradical dicationic cyclophanes with tunable cavity sizes are investigated as new bisradical dicationic hosts for accommodating the methyl viologen radical cation (MV˙+) to form trisradical tricationic complexes. The structure–property relationships between cavity sizes and binding affinities have been established by comprehensive solution and solid-state characterizations as well as DFT calculations. The association constants of the four new trisradical tricationic complexes are found to range between 7400 and 170 000 M–1, with the strongest one being 4.3 times higher than that for [MV⊂BB]3(˙+). The facile accessibility and tunable stability of these new trisradical tricationic complexes make them attractive redox-controlled recognition motifs for further use in supramolecular chemistry and mechanostereochemistry.

Organic radicals are of importance in developing smart materials that have paramagnetic and/or near-infrared optical properties. Their practical applications, however, are limited by the labile nature of the radicals. Here, we demonstrate that by using a tetracationic cyclophane, namely, cyclobis(4,4'-(1,4-phenylene)bispyridine-p-phenylene) (ExBox4+), to encapsulate a naphthalenediimide (NDI) guest, the redox properties of NDI can be modulated. In organic solvents such as MeCN or DMF, ExBox4+ is able to provide the surrounding Coulombic attraction to the NDI•- radical anion and therefore enhance its stability toward oxidation. In water, NDI•- is prone to dimerization, forming its (NDI•-)2 dimer. Under UV-light irradiation, the (NDI•-)2 dimer is observed to disproportionate and yield the dianionic NDI2-. ExBox4+ is able to encapsulate the NDI•- radical anion and prevent its dimerization, and as a consequence, the radical anion is protected from further reduction in a noncovalent manner. We believe that our strategy of modulating the redox properties of NDI by either host-guest recognition or mechanical interlocking can aid and abet the development of radical-based materials, which could be employed in pursuit of applications in many areas, such as transporting spin and charges.

Summary Sophisticated architectures assembled from a single class of subunits by cooperative interactions are ubiquitous in nature. The construction of their artificial mimics, however, remains one of the most formidable challenges facing synthetic chemists. Here, we report a hierarchical diamondoid superstructure—namely, a supramolecular diamond—that is constructed from the multiple-level self-assembly of a highly symmetrical salt, hexakis[(4,4′-bipyridin-1-ium)methylene]benzene hexafluorophosphate. The uniform octahedral single crystals, with 96 cationic organic fragments and 96 counteranions in a unit cell, can be prepared quantitatively in a controllable one-step procedure within seconds at ambient conditions. The sizes of the resulting samples are modulated from 280 nm to 660 μm. The mechanism of the self-assembly was elucidated at the atomic level. As proof of its intrinsically cationic superstructure with mobile anions, the three-dimensional nanoporous framework can exchange efficiently with metal oxoanions. This research shows that precisely tunable hierarchical assemblies can translate charged molecules into complicated architectures.

For the most part, enzymes contain one active site wherein they catalyze in a serial manner chemical reactions between substrates both efficiently and rapidly. Imagine if a situation could be created within a chiral porous crystal containing trillions of active sites where substrates can reside in vast numbers before being converted in parallel into products. Here, we report how it is possible to incorporate 1-anthracenecarboxylate (1-AC-) as a substrate into a γ-cyclodextrin-containing metal-organic framework (CD-MOF-1), where the metals are K+ cations, prior to carrying out [4+4] photodimerizations between pairs of substrate molecules, affording selectively one of four possible regioisomers. One of the high-yielding regioisomers exhibits optical activity as a result of the presence of an 8:1 ratio of the two enantiomers following separation by high-performance liquid chromatography. The solid-state superstructure of 1-anthracenecarboxylate potassium salt (1-ACK), which is co-crystallized with γ-cyclodextrin, reveals that pairs of substrate molecules are not only packed inside tunnels between spherical cavities present in CD-MOF-1, but also stabilized-in addition to hydrogen-bonding to the C-2 and C-3 hydroxyl groups on the d-glucopyranosyl residues present in the γ-cyclodextrin tori-by combinations of hydrophobic and electrostatic interactions between the carboxyl groups in 1-AC- and four K+ cations on the waistline between the two γ-cyclodextrin tori in the tunnels. These non-covalent bonding interactions result in preferred co-conformations that account for the highly regio- and enantioselective [4+4] cycloaddition during photoirradiation. Theoretical calculations, in conjunction with crystallography, support the regio- and stereochemical outcome of the photodimerization.

Highly efficient removal of organic pollutants currently is a main worldwide concern in water treatment, and highly challenging. Here, vertically oriented mesoporous coatings (MCs) with tunable surface properties and pore sizes have been developed via the single-micelle directing assembly strategy, which show good adsorption performances toward a wide range of organic pollutants. The micelle size and structure can be precisely regulated by oil molecules based on their n-octanol/water partition coefficients (Log P) in the oil-water diphase assembly system, which are critical to the pore size and pore surface property of the MCs. The affinity and steric effects of the MCs can be on-demand adjusted, as a result, the MCs show a ultrahigh adsorption capacity (263 mg g-1 ), surface occupancy ratio (≈41.92%), and adsorption rate (≈10.85 mg g-1 min-1 ) for microcystin-LR, which is among the best performances up to date. The MCs also show an excellent universality to remove organic pollutants with different properties. Moreover, overcoming the challenges proposed by particulate absorbents, the MCs are stable and can be easily regenerated and reused without secondary contamination. This work paves a new route to the synthesis of high-quality MCs for water purification.

One ring threaded by two other rings to form a non-intertwined ternary ring-in-rings motif is a challenging task in noncovalent synthesis. Constructing multicolor photoluminescence systems with tunable properties is also a fundamental research goal, which can lead to applications in multidimensional biological imaging, visual displays, and encryption materials. Herein, we describe the design and synthesis of binary and ternary ring-in-ring(s) complexes, based on an extended tetracationic cyclophane and cucurbit[8]uril. The formation of these complexes is accompanied by tunable multicolor fluorescence outputs. On mixing equimolar amounts of the cyclophane and cucurbit[8]uril, a 1:1 ring-in-ring complex is formed as a result of hydrophobic interactions associated with a favorable change in entropy. With the addition of another equivalent of cucurbit[8]uril, a 1:2 ring-in-rings complex is formed, facilitated by additional ion-dipole interactions involving the pyridinium units in the cyclophane and the carbonyl groups in cucurbit[8]uril. Because of the narrowing in the energy gaps of the cyclophane within the rigid hydrophobic cavities of cucurbit[8]urils, the binary and ternary ring-in-ring(s) complexes emit green and bright yellow fluorescence, respectively. A series of color-tunable emissions, such as sky blue, cyan, green, and yellow with increased fluorescence lifetimes, can be achieved by simply adding cucurbit[8]uril to an aqueous solution of the cyclophane. Notably, the smaller cyclobis(paraquat-p-phenylene), which contains the same p-xylylene linkers as the extended tetracationic cyclophane, does not form ring-in-ring(s) complexes with cucurbit[8]uril. The encapsulation of this extended tetracationic cyclophane by both one and two cucurbit[8]urils provides an incentive to design and synthesize more advanced supramolecular systems, as well as opening up a feasible approach toward achieving tunable multicolor photoluminescence with single chromophores.

The ability to control the relative motions of component parts in molecules is essential for the development of molecular nanotechnology. The advent of mechanically interlocked molecules (MIMs) has enhanced significantly the opportunities for chemists to harness such motions in artificial molecular machines (AMMs). Recently, we have developed artificial molecular pumps (AMPs) capable of producing highly energetic oligo- and polyrotaxanes with high precision. Here, we report the design, synthesis, and operation of an AMP incorporating a photocleavable stopper that allows for the use of orthogonal stimuli. Our approach employs a ratchet mechanism to pump a ring onto a collecting chain, forming an intermediate [2]rotaxane. At a subsequent time, application of light triggers the release of the ring back into the bulk solution with temporal control. This process is monitored by the quenching of the fluorescence of a naphthalene-based fluorophore. This design may find application in the fabrication of molecular transporting systems with on-demand functions.

Developing an extremely efficient and highly selective process for gold recovery is urgently desired for maintaining a sustainable ecological environment. Herein, we report a highly efficient gold-recovery protocol on the basis of the instantaneous assembly between cucurbit[6]uril (CB[6]) and [AuX

Two new highly charged [2]catenanes—namely, mHe[2]C·6PF₆ and mHo[2]C·6PF₆—were synthesized by exploiting radical host–guest templation between derivatives containing BIPY•+ radical cations and the meta analogue of cyclobis(paraquat-p-phenylene). In contrast to related [2]catenanes that have been isolated as air-stable monoradicals, both mHe[2]C·6PF₆ and mHo[2]C·6PF₆ exist as air-stable singlet bisradicals, as evidenced by both X-ray crystallography in the solid state and EPR spectroscopy in solution. Electrochemical studies indicate that the first two reduction peaks of these two [2]catenanes are shifted significantly to more positive potentials, a feature which is responsible for their extraordinary stability in air. The mixed-valence nature of the mono- and bisradical states endows them with unique NIR absorption properties, e.g., NIR absorption bands for the mono- and bisradical states observed at ∼1800 and ∼1450 nm, respectively. These [2]catenanes are potentially useful in applications that include NIR photothermal conversion, UV–vis–NIR multiple-state electrochromic materials, and multiple-state memory devices. Our findings highlight the principle of “mechanical-bond-induced stabilization” as an efficient strategy for designing persistent organic radicals.

Along with the advent of supramolecular chemistry, research on fullerene receptors based on noncovalent bonding interactions has attracted a lot of attention. Here, we present the design and synthesis of a cationic molecular cage: a cyclophane composed of two tetraphenylporphyrins, bridged face-to-face by four viologen units in a rhomboid prismatic manner. The large cavity inside the cage, as well as the favorable donor–acceptor interactions between the porphyrin panels and the fullerene guests, enables the cage to be an excellent fullerene receptor. The 1:1 host–guest complexes formed between the cage and both C60 and C70 were characterized in solution by HRMS and NMR, UV–vis and fluorescence spectroscopies, and confirmed in the solid state by single-crystal X-ray diffraction analyses. The results from solution studies reveal that the cage has a much stronger binding for C70 than for C60, resulting in a selective extraction of C70 from a C60-enriched fullerene mixture (C60/C70 = 10/1), demonstrating the ...

A class of metal-organic frameworks (MOFs)-namely CD-MOFs-obtained from natural products has been grown in an epitaxial fashion as films on the surfaces of glass substrates, which are modified with self-assembled monolayers (SAMs) of γ-cyclodextrin (γ-CD) molecules. The SAMs are created by host-guest complexation of γ-CD molecules with surface-functionalized pyrene units. The CD-MOF films have continuous polycrystalline morphology with a structurally out-of-plane ( c-axial) orientation, covering an area of several square millimeters, with a thickness of ∼2 μm. Furthermore, this versatile host-guest strategy has been applied successfully in the growth of CD-MOFs as the shell on the curved surface of microparticles as well as in the integration of CD-MOF films into electrochemical devices for sensing carbon dioxide. In striking contrast to the control devices prepared from CD-MOF crystalline powders, these CD-MOF film-based devices display an enhancement in proton conductance of up to 300-fold. In addition, the CD-MOF film-based device exhibits more rapid and highly reversible CO2-sensing cycles under ambient conditions, with a 50-fold decrease in conductivity upon exposure to CO2 for 3 s which is recovered within 10 s upon re-exposure to air.

Herein, we report an unprecedented mixed-valence crystal superstructure that consists of a 2:1 host–guest complex [MV⊂(CBPQT)_2]^(2/3+) [MV = methyl viologen, CBPQT = cyclobis(paraquat-p-phenylene)]. One electron is distributed statistically between three [MV⊂(CBPQT)_2]•+ composed of a total of 15 viologen units. The mixed-valence state is validated by single-crystal X-ray crystallography, which supports an empirical formula of [MV⊂(CBPQT)_2]_3·(PF_6)_2 for the body-centered cubic superstructure. Electron paramagnetic resonance provides further evidence of electron delocalization. Quantum chemistry calculations confirm the mixed-valence state in the crystal superstructure. Our findings demonstrate that precise tuning of the redox states in host–guest systems can lead to a promising supramolecular strategy for achieving long-range electron delocalization in solid-state devices.

Synthetic macrocycles capable of undergoing allosteric regulation by responding to versatile external stimuli are the subject of increasing attention in supramolecular science. Herein, we report a structurally transformative tetracationic cyclophane containing two 3,6-bis(4-pyridyl)-l,2,4,5-tetrazine (4-bptz) units, which are linked together by two p-xylylene bridges. The cyclophane, which possesses modular redox states and structural post-modifications, can undergo two reversibly consecutive two-electron reductions, affording first its bisradical dicationic counterpart, and then subsequently the fully reduced species. Furthermore, one single-parent cyclophane can afford effectively three other new analogs through box-to-box cascade transformations, taking advantage of either reductions or an inverse electron-demand Diels-Alder (IEDDA) reaction. While all four new tetracationic cyclophanes adopt rigid and symmetric box-like conformations, their geometries in relation to size, shape, electronic properties, and binding affinities toward polycyclic aromatic hydrocarbons can be readily regulated. This structurally transformative tetracationic cyclophane performs a variety of new tasks as a result of structural post-modifications, thus serving as a toolbox for probing the radical properties and generating rapidly a range of structurally diverse cyclophanes by efficient divergent syntheses. This research lays a solid foundation for the introduction of the structurally transformative tetracationic cyclophane into the realm of mechanically interlocked molecules and will provide a toolbox to construct and operate intelligent molecular machines.

A novel heterostructured Si@C@Ge anode is developed via a two-step sol–gel method. A facile and straightforward Ge decoration significantly boosts the Li-storage performance of core–shell Si@C nanoparticles on both mechanics and kinetics. The Si@C@Ge anode shows unprecedented electrochemical performance in terms of accessible capacity, cycling stability, and rate capability when compared to those of a core–shell Si@C anode. Based on the experimental results and analysis of the mechanism, it is evident that high-conductivity Ge nanograins on the surface facilitates the Li diffusivity and electron transport and guarantees high ion accessibility. Moreover, it is the Ge nanograins that serve as buffering cushion to tolerate the mechanic strain distribution on the electrode during lithiation/delithiation processes.

Indoor organic gaseous pollution is a global health problem, which seriously threats the health and life of human all over the world. Hence, it is important to fabricate new sensing materials with high sensitivity and efficiency for indoor volatile organic compounds. In this study, a series of ordered mesoporous silica-based nanocomposites with uniform carbon coatings on the internal surface of silica mesopore channels were synthesized through a simple template-carbonization strategy. The obtained mesoporous silica-carbon nanocomposites not only possess ordered mesostructures, high surface areas (up to ∼759m(2)g(-1)), large and tunable pore sizes (2.6-10.2nm), but also have the improved hydrophobicity and anti-interference capability to environmental humidity. The sensing performances of the mesoporous silica-carbon nanocomposites to volatile organic compounds, such as ethylbenzene, methylbenzene, benzene, methanol, acetone, formaldehyde, dichloromethane and tetrahydrofuran, were systematically investigated. The relationships between the sensing performances and their properties, including mesostructures, surface areas, pore sizes, carbon contents and surface hydrophilic/hydrophobic interactions, have been achieved. The mesoporous silica-carbon nanocomposites with hexagonal mesostructure exhibit outstanding performance at room temperature to benzene and acetone with high responses, short response (2-3s) and recovery (16-19s) time, strong anti-interference to environmental humidity, and long-term stability (less than ∼5% loss of the frequency shifts after 42days). Therefore, the obtained mesoporous silica-carbon nanocomposites have a hopeful prospect in the field of environmental air quality monitoring.

Designing macrocycles with appropriate molecular recognition features that allow for the integration of suitable external stimuli to control host-guest processes is a challenging endeavor which enables molecular containers to solubilize, stabilize, and separate chemical entities in an externally controllable manner. Herein, we introduce photo- and thermal-responsive elements into a semi-rigid tetracationic cyclophane, OPVEx2Box4+, that is composed of oligo( p-phenylenevinylene) pyridinium units and the biphenylene-bridged 4,4-bipyridinium extended viologens and adopts a rectangle-like geometry. It transpires that when the photoactive oligo( p-phenylenevinylene) pyridinium unit is incorporated in a macrocyclic scaffold, its reversibility is dramatically improved, and the configurations of the cyclophane can go back and forth between ( EE)- and ( EZ)-isomers upon alternating blue light irradiation and heating. When the macrocycle is found in its ( EE)-configuration, it is capable of binding various π-electron-rich guests-e.g., anthracene and perylene-as well as π-electron-deficient guests-e.g., 9,10-anthraquinone and 5,12-tetracenequinone-through charge-transfer and van der Waals interactions. When irradiated with blue light, the ( EE)-isomer of the cyclophane can be transformed successfully to the ( EZ)-isomer, resulting in the switching off of the binding affinity for guest molecules, which are bound once again upon heating. The use of light and heat as external stimuli to control host-guest interactions involving a multi-responsive host and various guests provides us with a new opportunity to design and construct more-advanced molecular switches and machines.

Along with the advent of supramolecular chemistry, research on fullerene receptors based on noncovalent bonding interactions has attracted a lot of attention. Here, we present the design and synthesis of a cationic molecular cage: a cyclophane composed of two tetraphenylporphyrins, bridged face-to-face by four viologen units in a rhomboid prismatic manner. The large cavity inside the cage, as well as the favorable donor-acceptor interactions between the porphyrin panels and the fullerene guests, enables the cage to be an excellent fullerene receptor. The 1:1 host-guest complexes formed between the cage and both C

Summary Highly efficient cell-free enzymatic systems are typically difficult to achieve in traditional immobilized enzyme systems because of the lack of optimal spatial control of enzyme localization, substrate and product diffusion, and enzyme and coenzyme accessibility. Here, we report a strategy for expanding the pore apertures (from 3.3 to 6.7 nm) of a series of Zr-based metallic-organic frameworks (MOFs) (termed NU-100x , x = 3, 4, 5, 6, 7) with interconnected hierarchical pores by maintaining precise control of torsional angles associated with the linkers. As a proof of concept, we use the expanded NU-100x MOF structures to encapsulate lactate dehydrogenase (LDH) and demonstrate the use of the captured protein in a cell-free biosynthetic catalytic system. Remarkably, LDH immobilized in the large pores of the MOF is accessible to nicotinamide adenine dinucleotide coenzymes (NAD and NADH), allowing for in situ coenzyme regeneration leading to higher activity than that of the free enzyme.

Rational design and controllable synthesis of TiO2 based materials with unique microstructure, high reactivity, and excellent electrochemical performance for lithium ion batteries are crucially desired. In this paper, we developed a versatile route to synthesize hollow TiO2/graphitic carbon (H-TiO2/GC) spheres with superior electrochemical performance. The as-prepared mesoporous H-TiO2/GC hollow spheres present a high specific surface area (298 m(2) g(-1)), a high pore volume (0.31 cm(3) g(-1)), a large pore size (∼5 nm), well-defined hollow structure (monodispersed size of 600 nm and inner diameter of ∼400 nm, shell thickness of 100 nm), and small nanocrystals of anatase TiO2 (∼8 nm) conformably encapsulated in ultrathin graphitic carbon layers. As a result, the H-TiO2/GC hollow spheres achieve excellent electrochemical reactivity and stability as an anode material for lithium ion batteries. A high specific capacity of 137 mAh g(-1) can be achieved up to 1000 cycles at a current density of 1 A g(-1) (5 C). We believe that the mesoporous H-TiO2/GC hollow spheres are expected to be applied as a high-performance electrode material for next generation lithium ion batteries.

Here, we report the synthesis of reduced graphene oxide@mesoporous silica (denoted as rGO@mSiO2) sandwich-like sheets by an oil–water biphase stratification approach. The resultant rGO@mSiO2 nanosheets possess a uniform sandwich-like structure, ultrathin thickness (∼50 nm), large aspect ratio, high surface area (∼755 m2/g), and enlarged and tunable pore size (from 2.8 to 8.9 nm). Significantly, the mesochannels are oriented perpendicularly to graphene surfaces and shaped like a funnel, which facilitates drug loading and releasing. The influences of the concentration of precursor, solvent, GO sheet, and reaction temperature on the formation of the sandwich-like rGO@mSiO2 nanosheets have been systematically investigated. The resultant nanosheets with a pore size of ∼8.9 nm show the maximum loading capacity of bovine β-lactoglobulin (55.1 wt %). The protein releasing process in the simulated body fluid suggests that the release can be controlled from 20 to 60 h simply by adjusting the pore size. In addition,...

The rational design and precise synthesis of multifunctional hybrid nanostructures with a tailored active core and a large, dendritic, modified mesoporous structured shell can promote catalysis, energy storage, and biological applications. Here, an oil-water biphase stratification coating strategy has been developed to prepare monodisperse magnetic dendritic mesoporous silica core-shell structured nanospheres. These sophisticated Fe3O4@SiO2@dendritic-mSiO2 nanospheres feature large dendritic open pores (2.7 and 10.3 nm). Significantly, the silica shells can be converted into dendritic mesoporous aluminosilicate frameworks with unchanged porosity, a Si/Al molar ratio of 14, and remarkably strong acidic sites, through a post-synthesis approach. In addition, the resultant magnetic dendritic mesoporous aluminosilicate nanospheres exhibit outstanding properties and promising application in phosphate removal from wastewater.

Multiplexed detection technology has been attractive for its simultaneous assay of several analytes, which play significant roles in applications such as screening for combinatorial chemistry, genetic analysis, and clinical diagnostics. This work reports a novel and potentially powerful encoding system based upon dispersible suspension arrays of multilayer rare earth core/shell nanoparticles that are capable of multiplexed, high-sensitivity reporting for biomolecule detection by the Z-contrast imaging. These nanobarcode arrays are encoded by nanostructure design based on different atomic numbers. With the well-resolved high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) decoding technique, many thousands of unique nanobarcodes can be identified by multilayer core/shell nanostructure. Their applications to multiplexed biodetection of DNA demonstrated the highly sensitive (picomole) features of this novel nanobarcode system.

Correction for ‘Tuning radical interactions in trisradical tricationic complexes by varying host-cavity sizes’ by Kang Cai et al., Chem. Sci., 2020, DOI: 10.1039/c9sc04860j.

Organic functionalization and structural control of mesoporous materials are important for their applications. This study reports here that yolk–shell structured mesoporous nanoparticles with thioether-bridged organosilica frameworks can be successfully prepared by hydrothermal treatment of mesostructured organic–inorganic hybrid nanospheres. The thioether-bridged yolk–shell nanoparticles have ultrahigh condensation degree, i.e., (T3+Q4)/(Qn+Tm) = 94%, large surface area (400 m2 g–1), accessible ordered mesochannels (2.0 nm), large pore volume (0.67 cm3 g–1), and uniform diameter (290–90 nm), core size (180–40 nm), and shell thickness (19–8 nm). Thanks to the abundant thioether groups and the unique structure, the yolk–shell mesoporous nanoparticles can be used as nanoreactors to generate in situ polyhedral gold nanoparticles into their hollow spaces in a hot tetrachloride aurate aqueous solution. The gold loaded yolk–shell nanoparticles show two strong plasmon resonance bands at 577 and 633 nm with excel...

A magnesiothermic reduction approach is designed to synthesize mesoporous Si/C nanocomposites with ultrasmall, uniform silicon nanoparticles (ca. 3 nm) embedded in a rigid mesoporous carbon framework. The resultant mesoporous Si/C nanocomposites present excellent performance with high reversible capacity, good Coulombic efficiency and rate capability, and outstanding cycling stability in lithium-ion battery applications.

A kind of novel uniform monodispersed three-dimensional dendritic mesoporous silica nanospheres (3D-dendritic MSNSs) has been successfully synthesized for the first time. The 3D-dendritic MSNSs can have hierarchical mesostructure with multigenerational, tunable center-radial, and dendritic mesopore channels. The synthesis was carried out in the heterogeneous oil-water biphase stratification reaction system, which allowed the self-assembly of reactants taking place in the oil-water interface for one-pot continuous interfacial growth. The average pore size of each generation for the 3D-dendritic MSNSs can be adjusted from 2.8 to 13 nm independently, which can be controlled by the varied hydrophobic solvents and concentration of silica source in the upper oil phase. The thickness of each generation can be tuned from ∼ 5 to 180 nm as desired, which can be controlled by the reaction time and amount of silica source. The biphase stratification approach can also be used to prepare other core-shell and functional mesoporous materials such as Au nanoparticle@3D-dendritic MSNS and Ag nanocube@3D-dendritic MSNS composites. The 3D-dendritic MSNSs show their unique advantage for protein loading and releasing due to their tunable large pore sizes and smart hierarchical mesostructures. The maximum loading capacity of bovine β-lactoglobulin with 3D-dendritic MSNSs can reach as high as 62.1 wt % due to their large pore volume, and the simulated protein releasing process can be tuned from 24 to 96 h by flexible mesostructures. More importantly, the releasing rates are partly dependent on the hierarchical biodegradation, because the 3D-dendritic MSNSs with larger pore sizes have faster simulated biodegradation rates in simulated body fluid. The most rapid simulated biodegradation can be finished entirely in 24 h, which has been greatly shortened than two weeks for the mesoporous silica reported previously. As the inorganic mesoporous materials, 3D-dendritic MSNSs show excellent biocompatibility, and it would have a hopeful prospect in the clinical applications.

Membrane separation technologies are of great interest in industrial processes such as water purification, gas separation, and materials synthesis. However, commercial filtration membranes have broad pore size distributions, leading to poor size cutoff properties. In this work, mesoporous silica thin membranes with uniform and large vertical mesochannels are synthesized via a simple biphase stratification growth method, which possess an intact structure over centimeter size, ultrathin thickness (≤50 nm), high surface areas (up to 1420 m2 g−1), and tunable pore sizes from ≈2.8 to 11.8 nm by adjusting the micelle parameters. The nanofilter devices based on the free‐standing mesoporous silica thin membranes show excellent performances in separating differently sized gold nanoparticles (>91.8%) and proteins (>93.1%) due to the uniform pore channels. This work paves a promising way to develop new membranes with well‐defined pore diameters for highly efficient nanosize‐based separation at the macroscale. Y.L. and D.S. contributed equally to this work. This work was supported by the State Key Basic Research Program of the PRC (2012CB224805, 2013CB934104, and 2016YFA0204000), Shanghai Science and Technology Committee (14JC1400700), and NSF of China (grant nos. 21210004 and 21603036). The authors extend their appreciation to the International Scientific Partnership Program ISPP at King Saud University for funding this research work through ISPP# 0018. The authors gratefully thank Guangrong Zhou from The Key Laboratory of Molecular Engineering of Polymer and Department of Macromolecule Science (Fudan University) for the structural characterization and data analysis. Scopus

One pot successive layer-by-layer (SLBL) strategy is introduced to fabricate the core/shell upconversion nanoparticles (NPs) for the first time by using high boiling-point Re-OA (rare-earth chlorides dissolved in oleic acid at 140 °C) and Na-TFA-OA (sodium trifluoroacetate dissolved in oleic acid at room temperature) as shell precursor solutions. This protocol is flexible to deposit uniform multishell on both hexagonal (β) and cubic (α) phase cores by successive introducing of the shell precursor solutions. Shell thickness of the obtained NPs with narrow size distribution (σ < 10%) can be well controlled from 1 monolayer (∼0.36 nm) to more than 20 monolayers (∼8 nm) by simply tuning the amounts of the shell precursors. Furthermore, the tunable doping positions (core doping and shell doping) can also be achieved by adjusting the species and addition sequence of the shell precursors. As a result of the high quality uniform shell and advanced core/shell structures, the optical properties of the obtained core...

In this manuscript, a novel strategy for the therapeutic delivery of nitric oxide to physiological targets is described. Nitric oxide (NO) is a key vasodilator in mammalian cardiovascular systems and has been shown to sensitize tissue to γ -radiation. However, photochemical NO precursors that can be activated by these near-infrared (NIR) wavelengths are extremely limited. Herein, we have addressed this issue by utilizing the known NIR to visible upconversion properties of lanthanide cations doped NaYF 4 nanocrystals. This result is a potential game changer in multiphoton excitation based therapeutic delivery of NO and other small molecule bioregulators. The bioregulatory molecule nitric oxide (NO) plays important roles in cancer biology and has been implicated in both tumor growth and suppression. [ 1 ] Furthermore, NO is a γ -radiation sensitizer that can enhance selective killing of neoplastic tissues. For these reasons, there is considerable interest in developing methods for NO delivery to specifi c physiological targets. In this context, several laboratories have explored photoactivated NO delivery to specifi c tissues upon demand. [ 2‐7 ] A key advantage of photochemical triggering

Anticoagulation factor II (ACF II), a coagulation factor X- binding protein from the venom of Agkistrodon acutus has both anticoagulant and hypotensive activities. Previous studies show that ACF II binds specifically with activated factor X (FXa) in a Ca2+-dependent manner and inhibits intrinsic coagulation pathway. In this study, the inhibition of extrinsic coagulation pathway by ACF II was measured in vivo by prothrombin time assay and the binding of ACF II to factor IX (FIX) was investigated by native polyacrylamide gel electrophoresis and surface plasmon resonance (SPR). The results indicate that ACF II also inhibits extrinsic coagulation pathway, but does not inhibit thrombin activity. ACF II also binds with FIX with high binding affinity in a Ca2+-dependent manner and their maximal binding occurs at about 0.1 mM Ca2+. ACF II has similar binding affinity to FIX and FX as determined by SPR. Ca2+ has a slight effect on the secondary structure of FIX as determined by circular dichroism spectroscopy. Ca2+ ions are required to maintain in vivo function of FIX Gla domain for its recognition of ACF II. However, Ca2+ at high concentrations (>0.1 mM) inhibits the binding of ACF II to FIX. Ca2+ functions as a switch for the binding between ACF II and FIX. ACF II extends activated partial thromboplastin time more strongly than prothrombin time, suggesting that the binding of ACF II with FIX may play a dominant role in the anticoagulation of ACF II in vivo. © 2012 Wiley Periodicals, Inc. Biopolymers 97: 818–824, 2012.

Anticoagulation factor I (ACF I), a snake C-type lectin (snaclec) from the venom of Agkistrodon acutus binds specifically with activated factor X (FXa) in a Ca2+-dependent manner and prolongs the blood-clotting time in vitro. In this study, the inhibition of the coagulation pathway by ACF I was measured in vivo by activated partial thromboplastin time and prothrombin time assays and the binding of ACF I to factor IX (FIX) was investigated by native PAGE and surface plasmon resonance. The results indicate that ACF I inhibits both intrinsic and extrinsic coagulation pathways, but does not inhibit thrombin activity. ACF I also binds FIX in a Ca2+-dependent manner and their maximal binding occurs at 0.25 mM Ca2+. ACF I has a higher binding-affinity to FIX than to FX. Ca2+ is required to maintain in vivo function of FIX Gla domain for its recognition of ACF I. However, Ca2+ at high concentrations (>0.25 mM) inhibits the binding of ACF I to FIX. Ca2+ functions as a switch for the binding between ACF I and FIX. The results suggest that the binding of ACF I with FIX may play a dominant role in the anticoagulation activity of ACF I in vivo.

Factor IX-binding protein (AHP IX-bp), a Ca2+- and Zn2+-binding protein from the venom of Agkistrodon Halys Pallas was reported to bind specifically with factor IX in a Zn2+-dependent manner. Here we have purified AHP IX-bp by a simple two-step of chromatography procedure and found that AHP IX-bp also binds factor Xa (FXa) with high binding-affinity in a Mg2+-dependent manner. Although Mg2+ ions have a significantly low binding-affinity for apo-AHP IX-bp as determined by isothermal titration calorimetry, they can induce the binding of apo-AHP IX-bp with FXa even in the absence of Ca2+ as determined by native PAGE and surface plasmon resonance. Mg2+ ions are required to maintain in vivo function of FX Gla domain for its recognition of AHP IX-bp. Both Ca2+ and Zn2+ ions fail to induce the binding between apo-AHP IX-bp and FXa. The abundant Mg2+ ions in blood play an important role in the anticoagulation of AHP IX-bp.

AA-NADase from Agkistrodon acutus venom is a unique multicatalytic enzyme with both NADase and AT(D)Pase activities. Among all identified NADases, only AA-NADase contains Cu(II) and has disulfide-bond linkages between two peptide chains. The effects of the reduction of the disulfide-bonds and Cu(II) in AA-NADase by small-molecule reductants on its NADase and ADPase activities have been investigated by polyacrylamide gel electrophoresis, high performance liquid chromatography, electron paramagnetic resonance spectroscopy and isothermal titration calorimetry. The results show that AA-NADase has six disulfide-bonds and fifteen free cysteine residues. L-ascorbate inhibits AA-NADase on both NADase and ADPase activities through the reduction of Cu(II) in AA-NADase to Cu(I), while other reductants, dithiothreitol, glutathione and tris(2-carboxyethyl)phosphine inhibit both NADase and ADPase activities through the reduction of Cu(II) to Cu(I) and the cleavage of disulfide-bonds in AA-NADase. Apo-AA-NADase can recover its NADase and ADPase activities in the presence of 1 mM Zn(II). However, apo-AA-NADase does not recover any NADase or ADPase activity in the presence of 1 mM Zn(II) and 2 mM TCEP. The multicatalytic activity relies on both disulfide-bonds and Cu(II), while Cu(I) can not activate the enzyme activities. AA-NADase is probably only active as a dimer. The inhibition curves for both ADPase and NADase activities by each reductant share a similar trend, suggesting both ADPase and NADase activities probably occur at the same site. In addition, we also find that glutathione and L-ascorbate are endogenous inhibitors to the multicatalytic activity of AA-NADase.