Triply Interlocked [2]catenanes: Rational Synthesis, Reversible Conversion Studies and Unprecedented Application in Photothermal Responsive Elastomer.

Triply interlocked [2]catenane complexes featuring two identical, mechanically interlocked units are extraordinarily rare chemical compounds, whose properties and applications remain open to detailed studies. Herein, we introduce the rational design of a new ligand precursor, L1, suitable for the synthesis of six triply interlocked [2]catenanes by coordination-driven self-assembly. The interlocked compounds can be reversibly converted into the corresponding simple triangular prism metallacage by addition of H2O or DMF solvents to their CH3OH solutions, thereby demonstrating the importance of π···π stacking and hydrogen bonding interactions in the formation of triply interlocked [2]catenanes. Moreover, extensive studies have been conducted to assess the remarkable photothermal conversion performance. Complex 6a, exhibiting outstanding photothermal conversion performance (conversion efficiency in solution : 31.82%), is used to prepare novel photoresponsive elastomer in combination with thermally activated liquid crystal elastomer. The resultant material displays robust response to near-infrared (NIR) laser and the capability of completely reforming the shape and reversible actuation, paving the way for the application of half-sandwich organometallic units in photo-responsive smart materials.

Self-Assembly and Photothermal Conversion of MetallaRussian Doll and Metalla[2]catenanes Induced via Multiple Stacking Interactions.

A variety of organometallic supramolecular architectures have been constructed over the past decades and their properties were also explored via different strategies. However, the synthesis of metalla-Russian doll is still a fascinating challenge. Herein, a series of new coordination supramolecular complexes, including a metalla-Russian doll, metalla[2]catenanes, and metallarectangles, were synthesized by using meticulously selected Cp*Rh (Cp* = η5-C5Me5) building units (E1, E2, and E3) and three rigid anthracylpyridine ligands (L1, L2, and L3) via a self-assembly strategy. While the combination of the short ligand L1 and E1 or E2 generated two metallarectangles, the longer ligand L2 containing an alkynyl group resulted in two new [2]catenanes, most likely due to which the strong electron-donating effect of alkynyl groups causes self-accumulation. Interestingly, an unusual Russian doll assembly was obtained through the reaction of L3 and E3 based on sextuple π···π stacking interactions. Furthermore, the dynamic structural conversion between [2]catenanes and the corresponding metallarectangles could be observed through concentration-, solvent-, and guest-induced effects. The [2]catenane complexes 4b displayed efficient photothermal conversion efficiency in solution (20.2%), in comparison with other organometallic macrocycles. We believe that π···π stacking interactions generate active nonradiative pathways and promote radiative photodeactivation pathways. This study proves the versatility of half-sandwich building units, not only to build complicated supramolecular topologies but also in effective functional materials for various appealing applications.

Direct White-Light Emitting From a Single Metal-Organic Framework with Dual Phosphorescence Peaks.

Single component white-light-emitting (SCWLE) materials are extremely desired in the field of solid-state lighting. However, pure-phosphorescent SCWLE has rarely been reported. Herein, one halogen-bonding-containing MOF [Cd(5-BIPA)(phen)] (1) has been synthesized, which shows efficient white-light emission originating from dual phosphorescence bands with different wavelengths and lifetimes. The fabrication of a phosphor-converted white-light-emitting diode device driven by pulsing current enables this MOF to be a promising phosphor.

Fast photocatalytic degradation of rhodamine B using indium-porphyrin based cationic MOF under visible light irradiation.

A broad light-harvesting range and efficient charge separation are two main ways to enhance the visible photocatalytic performance of semiconductors. Herein, an ionic porphyrin MOF [In(TPyP)]·(NO3) (1) (TPyP = 5,10,15,20-tetrakis(4-pyridyl)-21H,23H-porphyrin) was synthesized via in situ metalation. The orderly arranged porphyrin photosensitizer and the internal electric field between the MOF host and NO3- guests enable effective visible light response and electron-hole separation. Consequently, the as-synthesized MOF shows efficient photocatalytic degradation of rhodamine B (RhB), methyl orange (MO) and methylene blue (MB) organic pollutants. It can degrade 99.07% of RhB within only 20 minutes under visible light irradiation (λ > 420 nm) with a high chemical reaction rate constant of 0.2400 min-1. The photocatalytic activity of the title MOF is more efficient than those of other reported MOFs, COFs and even inorganic semiconductors. The reusability, energy level, band gap, charge distribution and main degradation mechanisms of the photocatalyst were well studied.

Enhanced Activity of Enzyme Immobilized on Hydrophobic ZIF-8 Modified by Ni2+ Ions.

The development of efficient enzyme immobilization to promote their recyclability and activity is highly desirable. Zeolitic imidazolate framework-8 (ZIF-8) has been proved to be an effective platform for enzyme immobilization due to its easy preparation and biocompatibility. However, the intrinsic hydrophobic characteristic hinders its further development in this filed. Herein, a facile synthesis approach was developed to immobilize pepsin (PEP) on the ZIF-8 carrier by using Ni2+ ions as anchor (ZIF-8@PEP-Ni). By contrast, the direct coating of PEP on the surface of ZIF-8 (ZIF-8@PEP) generated significant conformational changes. Electrochemical oxygen evolution reaction (OER) was employed to study the catalytic activity of immobilized PEP. The ZIF-8@PEP-Ni composite attains remarkable OER performance with an ultralow overpotential of only 127 mV at 10 mA cm-2 , which is much lower than the 690 and 919 mV overpotential values of ZIF-8@PEP and PEP, respectively.

Selective Synthesis and Structural Transformation of a 4-Ravel Containing Four Crossings and Featuring Cp*Rh/Ir Fragments.

Intricately interwoven topologies are continually being synthesized and are ultimately equally versatile and significant at the nanoscale level; however, reports concerning ravel structures, which are highly entwined new topological species, are extremely rare and fraught with tremendous synthesis challenges. To solve the synthesis problem, a tetrapodontic pyridine ligand L1 with two types of olefinic bond units and two Cp*M-based building blocks (E1, M=Rh; E2, M=Ir) featuring large conjugated planes was prepared to perform the self-assembly. Two unprecedented [5+10] icosanuclear molecular 4-ravels containing four crossings were obtained by parallel-displaced π⋅⋅⋅π interactions in a single-step strategy. Remarkably, reversible structural transformations between the 4-ravel and the corresponding metallocage could be realized by concentration changes and solvent- and guest-induced effects. X-ray crystallographic data and NMR spectroscopy provide full confirmation of these phenomena.

Anionic Porous Zn-Metalated Porphyrin Metal-Organic Framework with PtS Topology for Gas-Phase Photocatalytic CO2 Reduction.

Presented here are the synthesis and gas-phase photocatalytic CO2 reduction of an anionic porous Zn-metalated porphyrin metal-organic framework (MOF) induced by an ionic liquid. The desired CO2 affinity and deep conduction band position of the MOF catalyst provide strong kinetic and thermodynamic advantages for photocatalytic CO2 to CH4 conversion with high selectivity (∼70%) in H2O vapor.

Size-Induced Highly Selective Synthesis of Organometallic Rectangular Macrocycles and Heterometallic Cage Based on Half-Sandwich Rhodium Building Block.

The controlled synthesis of organometallic supramolecular macrocycles cages remains interesting and challenging work in the field of supramolecular chemistry. Here, two tetranuclear rectangular macrocycles and an octuclear cage were designed and synthesized utilizing a rigid and functionalized pillar linker, 2,6-bis(pyridin-4-yl)-1,7-dihydrobenzo [1,2-d:4,5-d']diimidazole (BBI4PY) based on three half-sandwich rhodium building blocks bearing different sizes. X-ray crystallography in combination with 1H NMR spectroscopy elucidated that the two building blocks with shorter spacers only result in rectangular macrocycles. However, the building block of bulkier size to avoid the π-π stacking interactions between two ligands BBI4PY led to the formation of an octuclear cage complex. The latter cage contains two types of metal ions, namely Rh3+ and Cu2+, showing significant characteristics of heterogeneous metal-assembling compounds. In addition, the cage accommodates two free isopropyl ether solvent molecules, thus displaying host-guest behavior.

Stable Zinc-Based Metal-Organic Framework Photocatalyst for Effective Visible-Light-Driven Hydrogen Production.

Herein, a new Zn-MOF material, [Zn(L1)(L2)], 1, was built successfully through a one-pot solvothermal method. The 3D MOF structure was determined by Single X-ray diffraction analysis, IR, and elemental analysis. A series of PXRD tests of 1 after being immersed in different solvents and pH solutions demonstrated the good stability of 1. Interestingly, this material displayed high catalytic activity for the visible-light-driven hydrogen generation under the illumination of white LED in pure water or a mixture of DMF and H2O without additional photosensitizers and cocatalysts. Besides, the studies also showed that the catalytic activity changed constantly as well as the solvent ratio adjustment of DMF and H2O from 4:6 to 2:8. Additionally, the catalytic activity reached the best value (743 µmol g-1 h-1) when the solvent ratio was 4:6. The heterogeneous nature and recyclability of the MOF catalyst, as well as several factors that affect the catalytic activity, were investigated and described in detail. Moreover, the photocatalytic mechanism for the hydrogen generation of 1 was also proposed based on the fluorescence spectra and UV-vis absorption.

Iron Porphyrin as a Cytochrome P450 Model for the Degradation of Dye.

Organic dyes are widely used in the textile, biological, medical and other fields. However, a serious environmental problem has appeared because of the presence of organic dyes in industrial aqueous effluents. Thus, the efficient treatment of organic dyes in industrial wastewaters is currently in real demand. The current study investigated the oxidative degradation of the organic dye gentian violet by meso-tetra(carboxyphenyl) porphyriniron(III), [FeIII(TCPP)] as a cytochrome P450 model and iodosylbenzene (PhIO) as an oxidant at room temperature. The degradation reaction was monitored by UV-vis absorption spectroscopy via the observation of UV-vis spectral changes of the gentian violet. The results showed that the efficiency of catalyzed degradation reached more than 90% in 1 h, indicating the remarkable oxidative degradation capacity of the [FeIII(TCPP)]/PhIO system, which provided an efficient approach for the treatment of dyeing wastewater.

Long Afterglow of a Nonporous Coordination Polymer with Tunable Room-Temperature Phosphorescence by the Doping of Dye Molecules.

Metal-organic frameworks (MOFs) or coordination polymers (CPs)-based phosphorescence materials may provide a powerful route for photoelectric and optical recording devices. Herein, two phosphorescence ligands, iso-phthalic acid (IPA) and 2-methylimidazole (MIM), were selected to construct an nonporous CP {Zn(IPA)(MIM)2} (1) with a long-lived phosphorescence lifetime up to 552 ms. By the doping of Eosin Y (EY) dye molecules under an in situ process, the phosphorescence emission color of 1 can be expressly tuned from green to red. The light-harvesting range can also be vastly broadened from the UV to the visible region (550 nm). Photoelectron measurements reveal that the synergistic effect of bias voltage and illumination can greatly restrain electron-hole recombination for the generation of additional free charges.

Angle-Dependent Polarized Emission and Photoelectron Performance of Dye-Encapsulated Metal-Organic Framework.

Molecule-based crystalline materials with angle-dependent polarized emission have attracted considerable attention owing to their extensive applications in displays and anticounterfeiting. Herein, one anionic metal-organic framework (MOF) {[Zn2.5(µ3-OH)(NDC)2(HNDC)](HPIM)}n was constructed on the basis of an excellent photoactive ligand naphthalene-1,4-dicarboxylic acid (H2NDC). The protonated 2-propylimidazole (HPIM) guests residing in the nanochannels of MOF can be exchanged by a D-π-A cationic dye. The resulted host-guest system shows a rare example of ratiometric fluorescent polarizations and highly enhanced photoelectron performance in comparison with the pristine MOF.

Efficient Energy-Transfer-Induced High Photoelectric Conversion in a Dye-Encapsulated Ionic Pyrene-Based Metal-Organic Framework.

The relationship between the aggregation states of pyrene-based linkers and the photoluminescence/photoelectric performance was well studied by the formation of an anionic metal-organic framework, [BMI]2[Mg3(TBAPy)2(H2O)4]·2dioxane, which shows highly enhanced light-harvesting and photoelectric conversion efficiency by the encapsulation of D-π-A cation dyes.

Ultrafast Size Expansion and Turn-On Luminescence of Atomically Precise Silver Clusters by Hydrogen Sulfide.

The formation of high-nuclearity silver(I) clusters remains elusive and their potential applications are still underdeveloped. Herein, we firstly prepared a chain-like thiolated AgI complex {[Ag18 (St Bu)10 (NO3 )8 (CH3 CN)2 (H2 O)2 ] ⋅ [Ag18 (St Bu)10 (NO3 )8 (CH3 CN)6 ]}n (abbreviated as Ag18 ) in which two similar Ag18 clusters are assembled by NO3 - anions. The solution containing Ag18 reacted with hydrogen sulfide with controlled concentration, promptly producing another identifiable and bright red-emitting high-nuclearity silver(I) cluster, Ag62 (S)13 (St Bu)32 (NO3 )4 (abbreviated as Ag62 ). We tracked the transformation using time-dependent electrospray ionization mass spectrometry (ESI-MS), UV/Vis absorption and photoluminescence spectra. Based on this cluster transformation, we further developed an ultra-sensitive turn-on sensor detecting H2 S gas with an ultrafast response time (30 s) at a low detection limit (0.13 ppm). This work opens a new way of understanding the growth of metal clusters and developing their luminescent sensing applications.

Hexanuclear Zn(II)-Induced Dense π-Stacking in a Metal-Organic Framework Featuring Long-Lasting Room Temperature Phosphorescence.

A new strategy to enhance the room temperature phosphorescence performance has been developed through hexanuclear Zn(II)-cluster-induced dense π-stacking in a metal-organic framework matrix. The synergistic effect of metal clusters and large overlap of π-conjugated dimers facilitate the phosphorescence emission, migration, and separation of charge carriers for excellent photocatalytic activity.

Highly Dense Packing of Chromophoric Linkers Achievable in a Pyrene-Based Metal-Organic Framework for Photoelectric Response.

Highly dense packing of chromophoric linkers is achieved in a novel pyrene-based metal-organic framework (MOF), [Zn(TBAPy)1/2(H2O)2], induced by an ionic liquid. This MOF displays a quick response to visible-light irradiation (photocurrent density of up to 4.492 µA cm-2) and is capable of repetitive on-off photocurrent switching with a large on-off ratio (37.55).

Tetraphenylethylene-Decorated Metal-Organic Frameworks as Energy-Transfer Platform for the Detection of Nitro-Antibiotics and White-Light Emission.

The highly porous luminescent metal-organic frameworks (MOFs) can act as fluorescent probes for the detection of nitro compounds and can also serve as containers and energy transfer platforms to construct the host-guest systems. Herein, two new three-dimensional MOFs with high porosity were prepared successfully by the electron-rich tetrakis(4-pyridylphenyl)ethylene (tppe) as ligands. Compound 1 shows the high sensitivity and selectivity toward nitro-antibiotics in an aqueous media, particularly showing the best detection efficiency for furazolidone (FZD) among the reported luminescent sensors. The highly efficient fluorescence quenching toward FZD may be attributed to the electron and energy transfer. Compound 2 has naphthalene-2,7-dicarboxylic acid (2,7-npd) and tppe as dual linkers, and the energy transfer between 2,7-npd and tppe leads to the emission band in a large scale. It is worth noting that the single-phased white-light materials can be obtained by the in situ encapsulation of different concentration of sulforhodamine 101 (SR101) into compound 2 matrix.

{Zn6} Cluster Based Metal-Organic Framework with Enhanced Room-Temperature Phosphorescence and Optoelectronic Performances.

Molecule-based solid-state materials with long lifetimes could enable longer migration distances for excitons, which are beneficial for vast applications in optoelectronic field. Herein, we report a hexanuclear zinc cluster based MOF exhibits highly enhanced phosphorescence about 2 orders of magnitude in comparison with the pristine phosphor ligand. The combination of both experimental and computational results suggest that the {Zn6} cluster is very important for adjusting molecular conformations, packing arrangement, and photophysical properties of the organic phosphor ligands within the MOF matrix. Optoelectronic measurements reveal that the MOF-modified electrode is catalytically active to hydrogen evolution under light irradiation in neutral solution. Thus, our study provide an effective way to achieve low-cost metal-based phosphorescence MOF, expanding its further optoelectronic applications.

Bi-Microporous Metal-Organic Frameworks with Cubane [M4 (OH)4 ] (M=Ni, Co) Clusters and Pore-Space Partition for Electrocatalytic Methanol Oxidation Reaction.

Embedding cubane [M4 (OH)4 ] (M=Ni, Co) clusters within the matrix of metal-organic frameworks (MOFs) is a strategy to develop materials with unprecedented synergistic properties. Herein, a new material type based on the pore-space partition of the cubic primitive minimal-surface net (MOF-14-type) has been realized. CTGU-15 made from the [Ni4 (OH)4 ] cluster not only has very high BET surface area (3537 m2 g-1 ), but also exhibits bi-microporous features with well-defined micropores at 0.86 nm and 1.51 nm. Furthermore, CTGU-15 is stable even under high pH (0.1 m KOH), making it well suited for methanol oxidation in basic medium. The optimal hybrid catalyst KB&CTGU-15 (1:2) made from ketjen black (KB) and CTGU-15 exhibits an outstanding performance with a high mass specific peak current of 527 mA mg-1 and excellent peak current density (29.8 mA cm-2 ) at low potential (0.6 V). The isostructural cobalt structure (CTGU-16) has also been synthesized, further expanding the application potential of this material type.

Diblock Polymer Brush (PHEAA- b-PFMA): Microphase Separation Behavior and Anti-Protein Adsorption Performance.

In this paper, a series of amphiphilic diblock polymers of poly(hydroxyethylacrylamide)- b-poly(1H,1H-pentafluoropropyl methacrylate) (PHEAA- b-PFMA) were grafted from silicon wafer via surface-initiated atom transfer radical polymerization (SI-ATRP). Surface wettability and chemical compositions of the modified surfaces were characterized by contact angle goniometer and X-ray photoelectron spectroscopy (XPS) respectively. Molecular weight and polydispersity of each block were measured using gel permeation chromatography (GPC). The topography and the microphase separation behavior of PHEAA- b-PFMA surfaces were investigated by atomic force microscope (AFM). The results show that only when the grafting density (σ) and thickness of PHEAA brush were in the range of 0.9-1.3 (chain/nm2) and 6.6-15.1 nm, respectively, and the ratio of PFMA/PHEAA varied from 89/42 to 89/94, could the diblock copolymer phase separate into nanostructures. Further, the antiprotein adsorption performance of the modified surfaces against BSA, fibrinogen, and lysozyme was studied. The results indicated the modified surfaces could reduce the protein adsorption compared to the pristine silicon wafer. For Fibrinogen, the antiadsorption effect of PHEAA- b-PFMA-modified surfaces with microphase segregation was better than that of corresponding PHEAA modified surfaces. The results provide further evidence that surface composition and microphase segregation of fluorinated moieties of block copolymer brushes significantly impact protein adsorption behaviors.