Construction of Porous Polyureas and Polyamides via Domino Polymerization and Their High-Efficiency Au(III) Adsorption.

The adoption of new synthesis strategy and monomers significantly promotes the construction of porous organic polymers (POPs) and their promising applications. A fabricating method of porous polyimides is developed via sequential imidization and cross-linking reaction among self-condensable building blocks, as reported in the authors' previous manuscript. Herein, porous polyureas (A-POPs) are prepared starting from 4-ethynylaniline and diisocyanate monomers, while porous polyamides (B-POPs) are synthesized from 4-ethynylbenzoic acid and diisocyanate monomers. It is found that decreasing the monomer content in solvent can effectively inhibit the premature phase separation and facilitate the evolution of integrated network. Eventually, a maximum surface area of 425 m2  g-1 is achieved for porous polyureas when the content of monomers is 10%. To the best knowledge, A-POPs are the porous polyureas with the highest surface areas reported up to now. The as-prepared porous polyurea (AN-POP) exhibits the maximum adsorption capacity of 1093.87 ± 5.23 mg g-1 and removal rate of 99.96% for Au(III), due to its high surface area and the coordination between the heteroatoms (N and O) in A-POPs and metal ions. Besides, the porous polyurea also exhibits excellent renewable efficiency and high selectivity to Au(III).

Self-Assembly of Macrocyclic Triangles into Helicity-Opposite Nanotwists by Competitive Planar over Point Chirality.

While helix has elegant biomimetic structures and functionalities, it still remains a big question how the nanoscale helicity evolved from the molecular chiral building blocks across length scales. Herein, macrocyclic triangles composed of achiral edges and chiral vertices were rationally designed, in which the planar chirality emerged due to the restriction of edge rotation by intermolecular stackings and led to a unique chiral self-assembly. In contrast to the solution systems where the chiroptical property is exclusively dominated by the point chiral vertices, the emerged planar chirality was found to control the chiral self-assembly, resulting the nanotwist with the handedness determined by the planar chirality. Our work unveiled the self-assembly behaviors of macrocyclic conformers for the first time and provided a deep understanding on the macrocyclic chirality evolution including the excited-state chirality.

Excitation-Dependent Circularly Polarized Luminescence from Helical Assemblies Based on Tartaric Acid-Derived Acylhydrazones.

Here, we combined the merits of emergent excitation-dependent (ExD) emission and circularly polarized luminescence to develop an excitation-dependent circularly polarized luminescence (ExD CPL) material showing unique features. A series of acylhydrazones based on a chiral tartaric skeleton was designed and found to self-assemble into helical nanostructures through non-covalent bonds. The helical assemblies showed ExD CPL due to the cooperation of chirality transfer and excited state intramolecular proton transfer (ESIPT). Remarkably, not only the emission wavelength could be tuned by the excitation wavelength but the handedness of CPL could be modulated in an inverted or ON/OFF manner as well, thus leading to the first example of an ExD inverted or ON/OFF switchable CPL system. Time-dependent density functional theory (TD-DFT) calculations were carried out to explain the inversion of ExD CPL. This work provided a new insight into the unprecedented handedness controllable ExD CPL, which showcased a new paradigm of the advanced CPL materials.

Visible-light-induced cyclization of cyclic N-sulfonyl ketimines to N-sulfonamide fused imidazolidines.

A visible-light-induced metal-free cascade cyclization of cyclic N-sulfonyl ketimines with N-arylglycines for the construction of N-sulfonamide-fused imidazolidines was developed. The procedure employed 3 mol% of eosin Y as the photocatalyst at room temperature under visible light irradiation, providing various N-sulfonamide-fused imidazolidines in good yields (32 examples, up to 86% yields).

Pd-Pd/PdO as active sites on intercalated graphene oxide modified by diaminobenzene: fabrication, catalysis properties, synergistic effects, and catalytic mechanism.

Pd-Pd/PdO nanoclusters well dispersed on intercalated graphene oxide (GO) (denoted as GO@PPD-Pd) were prepared and characterized. GO@PPD-Pd exhibited high catalytic activity (a TOF value of 60 705 h-1) during the Suzuki coupling reaction, and it could be reused at least 6 times. The real active centre was Pd(200)-Pd(200)/PdO(110, 102). A change in the Pd facets on the surface of PdO was a key factor leading to deactivation, and the aggregation and loss of active centres was also another important reason. The catalytic mechanism involved heterogeneous catalysis, showing that the catalytic processes occurred at the interface, including substrate adsorption, intermediate formation, and product desorption. The real active centres showed enhanced negative charge due to the transfer of electrons from the carrier and ligands, which could effectively promote the oxidative addition reaction, and Pd(200) and the heteroconjugated Pd/PdO interface generated in situ also participated in the coupling process, synergistically boosting activity. Developed GO@PPD-Pd was a viable heterogeneous catalyst that may have practical applications owing to its easy synthesis and stability, and this synergistic approach can be utilized to develop other transition-metal catalysts.

Pen-writing high-quality perovskite films and degradable optoelectronic devices.

Paper is ubiquitous in the daily life and has been widely used for writing and drawing because of their low-cost, widely accessible, and degradable properties. However, simple ways to fabricate paper-based optoelectronic devices remain a great challenge. In this work, we report a facile method to fabricate high-quality perovskite films and optoelectronic devices on paper by direct pen-writing. Through introducing seed layers on papers, planar-integrated single-crystal perovskite films are easily prepared using commercial pens. Based on such a simple and convenient method, perovskite photodetector arrays and image sensors with graphite electrodes are fabricated on paper, and show satisfactory performances. This method provides a simple and effective approach for preparation of paper-based perovskite devices. It will be of significance for the development of degradable optoelectronic devices.

Interfacial Charge Transfer in a Hierarchical Ni2P/FeOOH Heterojunction Facilitates Electrocatalytic Oxygen Evolution.

The construction of a heterojunction is an important strategy to develop efficient electrocatalysts. However, the precise design and preparation of the heterojunction with desirable catalytic performance remain a challenge. Herein, a hierarchical Ni2P/FeOOH Schottky junction supported on nickel foam was prepared by electrodeposition of FeOOH on the surface of Ni2P. The electrocatalytic activity of the Ni2P/FeOOH Schottky junction can be remarkably improved, owing to the unique hierarchical architecture and strong electron interaction in the Ni2P/FeOOH Schottky junction. As-prepared Ni2P/FeOOH exhibits excellent electrocatalytic activity for an oxygen evolution reaction (OER) with an ultralow overpotential of 246 mV to reach 100 mA cm-2 and a small Tafel slope of 62.8 mV dec-1. This work provides not only a new method for the design of hierarchical nanomaterials but also an efficient strategy to design efficient OER electrocatalysts by constructing hierarchical heterojunctions.

A New ternary organometallic Pd(ii)/Fe(iii)/Ru(iii) self-assembly monolayer: the essential ensemble synergistic for improving catalytic activity.

The synergistic catalytic effect in a hetero-trimetallic catalytic monolayer is one of the intriguing topics because the additive effects of the second or third component play an important role in improving the activity. In this paper, a new Schiff-base organometallic nanosheet containing Pd/Fe/Ru immobilized on graphene oxide (GO@H-Pd/Fe/Ru) was prepared and characterized. The catalytic performance of GO@H-Pd/Fe/Ru and synergistic effect were systematically investigated. GO@H-Pd/Fe/Ru was found to be an efficient catalyst with higher turnover frequency (TOF) (26 892 h-1) and stability with recyclability of at least 10 times in the Suzuki-Miyaura coupling reaction. The deactivation mechanism was caused by the aggregation of the active species, loss of the active species, the changes of the organometallic complex, and active sites covered by adsorbed elements during the catalytic process. GO@H-Pd/Fe/Ru was a heterogeneous catalyst, as confirmed by kinetic studies with in situ FT-IR, thermal filtration tests and poisoning tests. The real active center containing Pd, Ru and Fe arranged as Fe(iii)-Ru(iii)-Pd(ii)-Fe(iii) was proposed. Although Ru(iii) and Fe(iii) were shown to be less active or inactive, the addition of Fe and Ru could effectively improve the entire activity by their ''indirect'' function, in which Fe or Ru made Pd more negative and more stable. The ensemble synergistic effect between metals, the ligand and support was described as a process in which the electron was transferred from GOvia ligand to Ru, and then to Pd or from Fe to Pd to make Pd more negative, promoting the oxidation addition with aryl halide. Also, the vicinity of Ru around Pd as the promoter adsorbed aryl boronic acid, which facilitates its synergism to react with the oxidation intermediate to the trans-metallic intermediate.

Preparation of Porous Carbon Materials Derived from Hyper-Cross-Linked Asphalt/Coal Tar and Their High Desulfurization Performance.

The development of simple and highly effective desulfurization technology is attracting more and more interest in both industrial and academic fields. Here, a new family of precursors was prepared based on hyper-cross-linked asphalt and coal tar building blocks. Thanks to the preintroduced porous structure, the precursors were converted into carbons with high surface area and large micropore volume via a uniform carbonization process. The synergistic effects of high surface area, abundant microporous structure, and the introduced polar functional groups endow the carbon materials with high desulfurization performance. The results of repeated experiments show that the adsorption capacities of five carbonized samples are higher than 40 mg S g-1, and the theoretical maximum adsorption capacity reaches 44.7 mg S g-1. Particularly, the adsorption equilibrium of all the carbonized samples can be reached in 5 min. Moreover, the recycle adsorption performance was also studied. Toluene exhibits the best elution effect among three eluents (iso-octane, para-xylene, and toluene) and the adsorption capacity remains 89% of the initial adsorption capacity after two adsorption-desorption cycles. It is believed that both innocent treatment of byproducts from petroleum industry and their high-value application for deep desulfurization in liquid hydrocarbon fuels benefit environmental protection and sustainable development.

Chiral Reticular Self-Assembly of Achiral AIEgen into Optically Pure Metal-Organic Frameworks (MOFs) with Dual Mechano-Switchable Circularly Polarized Luminescence.

Circularly polarized luminescence (CPL) is attractive in understanding the excited-state chirality and developing advanced materials. Herein, we propose a chiral reticular self-assembly strategy to unite achiral AIEgens, chirality donors, and metal ions to fabricate optically pure AIEgen metal-organic frameworks (MOFs) as efficient CPL materials. We have found that CPL activity of the single-crystal AIEgen MOF was generated by the framework-enabled strong emission from AIEgens and through-space chirality transfer from chirality donors to achiral AIEgens via metal-ion bridges. For the first time, a dual mechano-switched blue and red-shifted CPL activity was achieved via ultrasonication and grinding, which enabled the rotation or stacking change of AIEgen rotors with the intact homochiral framework. This work provided not only an insightful view of the aggregation induced emission (AIE) mechanism, but also an efficient and versatile strategy for the preparation of stimuli-responsive CPL materials.

Terpyridine-based Pd(ii)/Ni(ii) organometallic framework nano-sheets supported on graphene oxide-investigating the fabrication, tuning of catalytic properties and synergetic effects.

Tailoring the structures of catalysts and the arrangement of organic bimetallic catalysts are essential in both fundamental research and applications. However, they still impose enormous challenges such as size and active species distribution, ordered uniformity, and controllable composition, which are critical in determining their specific activities and efficiency. Herein, a novel terpyridine-based hetero-bimetallic Ni/Pd nanosheet supported on graphene oxide (denoted as GO@Tpy-Ni/Pd) was fabricated, which exhibited higher catalytic activity, substrate applicability and recyclability for the Suzuki coupling reaction under mild conditions. The catalytic mechanism was heterogeneous catalysis at the interface and the synergetic effect between Pd and Ni resulted in a little Ni(0)/Pd(0) cluster including Pd(ii)/Ni(ii) as a whole being formed through electron transfer on the catalytic surface. This phenomenon could be interpreted as the nanoscale clusters of Ni/Pd being the real active centre stabilized by the ligand and GO and the synergetic effect. The absorption and desorption of different substrates and products on Ni/Pd clusters, as calculated by DFT, was proved to be another key factor.

Ultra-High Performance of Hyper-Crosslinked Phosphate-Based Polymer for Uranium and Rare Earth Element Adsorption in Aqueous Solution.

In this work, a new type of hyper-crosslinked phosphate-based polymer (HCPP) polymerized by bis(2-methacryloxyethyl)phosphate has been developed for uranium and rare earth element (REE) extraction in an aqueous solution. The influence of the pH value, contact time, initial concentration, temperature, and competing ions on uranium adsorption of HCPP is investigated in detail. HCPP exhibits a maximum uranium adsorption capacity of up to 800 mg g-1 at pH = 6.0 and excellent selectivity toward uranium adsorption over coexisting ions, because of the high affinity between HCPP and uranium ions and dense phosphate groups on the backbone. It also demonstrates high adsorption performance in both simulated seawater with a high salt concentration and a real nuclear industrial effluent. Besides, the crosslinked network structure of HCPP endows this polymer with high chemical stability and reusability. Furthermore, the adsorption mechanism is probed by energy-dispersive spectroscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared measurements. It is confirmed that the adsorption of uranium on the adsorbent originates from the interaction between phosphate groups and uranium ions. Meanwhile, HCPP also displays high REE adsorption capacities. This work indicates that the phosphate-based HCPP could be utilized as a promising adsorbent for the effective removal of uranium and REEs from aqueous solution.

Facile Preparation of a Hierarchical C/rGO/FeO x Composite with Superior Microwave Absorption Performance.

A hierarchical carbon/reduced graphene oxide (rGO)/FeO x (CGF) composite has been successfully prepared utilizing a sequential process of immersion and carbonization. During the immersion of melamine foam in a liquid precursor, graphene oxide (GO) is covered on the interconnected framework of the foam and is decorated by metallic ions simultaneously. Therefore, the hierarchical structure is constructed in one step. The CGF composite exhibits a maximum reflection loss of as much as -51.2 dB and an ultrawide effective absorption bandwidth of 8.2 GHz. Detailed investigation suggests that the hierarchical structure contributes to the superb microwave absorption performance significantly through enhancing the interfacial polarization and inducing multireflection of microwave. The simple and cost-effective fabrication process together with the excellent microwave absorption performance endows the CGF composite with great potential for practical application.

Multifunctional BiF3:Ln3+ (Ln = Ho, Er, Tm)/Yb3+ nanoparticles: an investigation on the emission color tuning, thermosensitivity, and bioimaging.

Pure cubic phase and uniform BiF3:Ln3+ (Ln = Ho, Er, Tm)/Yb3+ nanoparticles (NPs) were prepared by coprecipitation. The growth mechanism of BiF3:2%Er3+/20%Yb3+ NPs was proposed based on evolution analysis of the time-dependent morphology, in which BiF3:2%Er3+/20%Yb3+ was formed through the growth process of "nucleation to crystallization and Ostwald ripening". The upconversion luminescence (UCL) properties and mechanism of BiF3:Ln3+ (Ln = Ho, Er, Tm)/Yb3+ under dual-wavelength excitation were also systematically investigated. The emission intensity of BiF3:2%Er3+/20%Yb3+ by dual-wavelength excitation (λ = 980 nm + 1550 nm) was 1.49 times more than that excited by 1550 nm or 980 nm individually. Furthermore, the properties of the bright white and multicolor UCL showed that yellow, purple, green, or pinkish light could be observed by controlling the doping concentration of Ln3+ (Ln = Yb, Er, Tm, and Ho), indicating that they had potential applications in backlight sources of color displays and security labeling. The temperature sensitivity of BiF3:2%Er3+/20%Yb3+ exhibited a downward tendency and its max value was about 0.0036 K-1 at 273 K. Cell toxicity tests showed that the UCNPs in phospholipid aqueous solution presented low cytotoxicity. Also, in vivo imaging and X-ray imaging revealed that the BiF3:2%Er3+/20%Yb3+ NPs had deep penetration and high contrast, which meant it could be used as a potential probe and contrast agent in in vivo optical bioimaging.

Quinoline-based ratiometric fluorescent probe for detection of physiological pH changes in aqueous solution and living cells.

Herein, a novel quinoline-based fluorescent probe DQPH has been developed for ratiometric detection of subtle pH fluctuation in biosystem. Upon altering the pH from 4.50 to 9.00, the emission spectra exhibit a large hypsochromic shift (57 nm) and the ratio of fluorescence intensity (F531 nm/F588 nm) changes from 0.30 to 1.36 with an ideal pKa value of 7.18 and a linear pH variation range of 6.35-8.00. The ratiometric response is attributed to the protonation-activable resonance charge transfer (PARCT) process, which has been proved by 1H NMR and NOESY experiment. This probe displayed good solubility, low cytotoxicity, anti-interference capability and reversible pH sensing. Furthermore, DQPH was successfully applied for monitoring pH changes in living cells.

A novel fluorescent probe for imaging the process of HOCl oxidation and Cys/Hcy reduction in living cells.

A new on-off-on fluorescent probe, CMOS, based on coumarin was developed to detect the process of hypochlorous acid (HOCl) oxidative stress and cysteine/homocysteine (Cys/Hcy) reduction. The probe exhibited a fast response, good sensitivity and selectivity. Moreover, it was applied for monitoring the redox process in living cells.

Fabrication and catalytic properties of ordered cyclopalladated diimine monolayer : investigation on catalytic mechanism.

"Channel-like" self-assembled monolayers having aliphatic and aromatic diimines (denoted as Si@1DIS, Si@2DIS and Si@3DIS) immobilized on substrates and their palladacycle monolayers (Si@1DIS-Pd, Si@2DIS-Pd and Si@3DIS-Pd) were prepared and characterized. Their catalytic performances were investigated using the Suzuki coupling reaction as a model. Si@3DIS-Pd showed the highest catalytic activity in water without ligands, and better recyclability than that of Si@2DIS-Pd and Si@1DIS-Pd. The reason was the carbon in the aliphatic diimine of Si@2DIS-Pd and Si@1DIS-Pd was easily hydrolyzed because of the active hydrogen of α-C, resulting in poor recyclability. Control of the amount of catalyst could be achieved by modulating the diameter of the channel-like structure, which also affected the catalytic activity. The catalytic process and mechanism were investigated systematically and proposed based on the experimental results obtained by the water contact angle, ultraviolet spectroscopy, X-ray photoelectron spectroscopy, cyclic voltammetry and atomic force spectroscopy. Changes in the morphology of monolayer surfaces during the catalytic process with or without stirring presented a clear process from order to disorder, and indicated that the reaction was a heterogeneous catalytic process occurring on the surface of the catalyst monolayer.

Facile Fabrication of Ordered Component-Tunable Heterobimetallic Self-Assembly Nanosheet for Catalyzing "Click" Reaction.

How to maximize the number of desirable active sites on the surface of the catalyst and minimize the number of sites promoting undesirable side reactions is currently an important research topic. In this study, a new way based on the synergism to achieve the successful fabrication of an ordered heterobimetallic self-assembled monolayer (denoted as BMSAM) with a controlled composition and an excellent orientation of metals in the monolayer was developed. BMSAM consisting of phenanthroline and Schiff-base groups was prepared, and its novel heterobimetallic (Cu and Pd) self-assembled monolayer anchored in silicon (denoted as Si-Fmp-Cu-Pd BMSAM) with a controlled composition and a fixed position was fabricated and characterized by UV, cyclic voltammetry, Raman, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), X-ray diffraction (XRD), inductively coupled plasma atomic emission spectroscopy (ICP-AES), and water-drop contact angle (WDCA) analyses. The effects of Si-Fmp-Cu-Pd BMSAM on its catalytic properties were also systematically investigated using "click" reaction as a template by WDCA, XPS, SEM, XRD, ICP-AES and in situ Fourier transform infrared analyses in a heterogeneous system. The results showed that the excellent catalytic characteristic could be attributed to the partial (ordered or proper distance) isolation of active sites displaying high densities of specific atomic ensembles. The catalytic reaction mechanism of the click reaction interpreted that the catalytic process mainly occurred on the surface of the monolayer, internal active site (Pd) and rationalized that the Cu(I) species and Pd(0) reduced from the Cu(II) and Pd(II) catalyst were active species, which had a proper distance between two different metals. The cuprate-triazole intermediate and the palladium intermediate, whose production is the key step, should lie in a proper position between the copper and active palladium sites, with which the reaction rate of transmetalation would be improved to increase the amount of the undesired Sonogashira coupling product.

A novel "tunnel-like" cyclopalladated arylimine catalyst immobilized on graphene oxide nano-sheet.

A novel "tunnel-like" cyclopalladated arylimine was prepared and immobilized on graphene oxide nano-sheet to form a hybrid catalytic material (denoted as F-GO-Pd) by self-assembly. The F-GO-Pd catalyst was characterized by XRD, FTIR, Raman, XPS, SEM, and TEM. This novel hybrid catalytic material was proven to be an efficient catalyst for the Suzuki-Miyaura coupling reaction of aryl halides (I, Br, Cl) with arylboronic acids in aqueous media under mild conditions with a very low amount of catalyst (0.01 mol%) and a high turnover frequency (TOF) (>20 000 h-1). In particular, high yields also could be obtained at room temperature with prolonged time. F-GO-Pd also showed good stability and recyclability seven times with a superior catalytic activity. The heterogeneous catalytic mechanism was investigated with kinetic studies, hot filtration tests, catalyst poisoning tests, and in situ FTIR spectroscopy with a ReactIR and the deactivation mechanism of the catalysts was proposed through analysis of its chemical stability by TEM, SEM, Raman, and XRD, indicating that a heterogeneous catalytic process occurred on the surface and the changes of the catalytic activity during the recycling were related to the micro-environment of the catalyst surface.

Sheet-like and truncated-dodecahedron-like AgI structures via a surfactant-assisted protocol and their morphology-dependent photocatalytic performance.

Silver halide-based structures have been attracting great interest as efficient visible-light-driven photocatalysts towards the photodegradation of organic pollutants, and those studies focusing on their morphology-dependent catalytic performances have received particular attention. While great advancements in this regard have been witnessed in the past few years with respect to AgCl- and AgBr-based photocatalysts, relevant explorations concerning AgI-based species are relatively rare, even though the excellent durability of AgI-based structures renders them attractive candidates for potential photocatalytic uses. By means of chemical reactions between AgNO3 and tetramethylammonium iodide (TMAI), and AgNO3 and tetrabutylammonium iodide (TBAI), we herein report that AgI structures with a sheet-like and a truncated-dodecahedron-like morphology, respectively, could be controllably synthesized via a surfactant-assisted fabrication protocol. In our synthesis systems, AgNO3 works as the silver source, while the TMAI and TBAI surfactants serve not only as an iodine source but also as a directing reagent for controllable fabrication. It has been demonstrated that our AgI structures could work as visible-light-energized photocatalysts towards the photodegradation of methyl orange. We find that compared to their sheet-like counterparts, the truncated-dodecahedron-like AgI architectures exhibit substantially boosted catalytic performances. Moreover, we disclose that our truncated-dodecahedron-like AgI-based species could display excellent photocatalytic stability, wherein their catalytic reactivity displays only trivial fluctuations under visible-light irradiation even after the photoreactions have been repeated 22 times continuously. Our work might not only introduce a facile protocol for the controllable synthesis of AgI structures but also pave an avenue for facile enhancement of their catalytic performances via morphology alterations.