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Owing to its prominent π‐delocalization and stability, vinylene linkage holds great merits in the construction of covalent organic frameworks (COFs) with promising semiconducting properties. However, carbon‐carbon double bond formation reaction always exhibits relatively low reversibility, unfavorable for the formation of high crystalline frameworks through self‐error correction and assembling processes. In this work, we report a heteroatom‐tuned strategy to build up a series of two‐dimensional (2D) vinylene‐linked COFs by Knoevenagel condensation of an electron‐deficient methylthiazolyl‐based monomer with different triformyl substituted (hetero−)aromatic derivatives. The resulting COFs show high‐quality periodic mesoporous structures with high surface areas. Embedding heteroatoms into the backbones enables significantly improving their crystallinity, and finely tailoring their semiconducting structures. Upon visible light stimulation, one of the as‐prepared COFs with donor‐π‐acceptor structure could deliver a nearly seven‐fold increase in the catalytic activity of hydrogen generation as compared with the other two. Meanwhile, in combination with high crystallinity and the matched conduction band energy level, such kind of COFs can be able to selectively generate singlet oxygen and superoxide radicals in a high ratio of up to 30 : 1, allowing for catalyzing aerobic thioanisole oxidation in distinctly tunable activities through the substituent electronic effect of the substrates. [ABSTRACT FROM AUTHOR]

Molecular phosphorescence in the second near‐infrared window (NIR‐II, 1000–1700 nm) holds promise for deep‐tissue optical imaging with high contrast by overcoming background fluorescence interference. However, achieving bright and stable NIR‐II molecular phosphorescence suitable for biological applications remains a formidable challenge. Herein, we report a new series of symmetric isocyanorhodium(I) complexes that could form oligomers and exhibit bright, long‐lived (7–8 μs) phosphorescence in aqueous solution via metallophilic interaction. Ligand substituents with enhanced dispersion attraction and electron‐donating properties were explored to extend excitation/emission wavelengths and enhanced stability. Further binding the oligomers with fetal bovine serum (FBS) resulted in NIR‐II molecular phosphorescence with high quantum yields (up to 3.93 %) and long‐term stability in biological environments, enabling in vivo tracking of single‐macrophage dynamics and high‐contrast time‐resolved imaging. These results pave the way for the development of highly‐efficient NIR‐II molecular phosphorescence for biomedical applications. [ABSTRACT FROM AUTHOR]

By integrating TiO2 with rare earth upconversion nanocrystals (NaREF4), efficient energy transfer can be achieved between the two subunits under near‐infrared (NIR) excitation, which hold tremendous potential in the fields of photocatalysis, photodynamic therapy (PDT), etc. However, in the previous studies, the combination of TiO2 with NaREF4 is a non‐epitaxial random blending mode, resulting in a diminished energy transfer efficiency between the NaREF4 and TiO2. Herein, we present a fluorine doping‐mediated epitaxial growth strategy for the synthesis of TiO2‐NaREF4 heteronanocrystals (HNCs). Due to the epitaxial growth connection, NaREF4 can transfer energy through phonon‐assisted pathway to TiO2, which is more efficient than the traditional indirect secondary photon excitation. Additionally, F doping brings oxygen vacancies in the TiO2 subunit, which further introduces new impurity energy levels in the intrinsic band gap of TiO2 subunit, and facilitates the energy transfer through phonon‐assisted method from NaREF4 to TiO2. As a proof of concept, TiO2‐NaGdF4 : Yb,Tm@NaYF4@NaGdF4 : Nd@NaYF4 HNCs were rationally constructed. Taking advantage of the dual‐model up‐ and downconversion luminescence of the delicately designed multi‐shell structured NaREF4 subunit, highly efficient photo‐response capability of the F‐doped TiO2 subunit and the efficient phonon‐assisted energy transfer between them, the prepared HNCs provide a distinctive nanoplatform for bioimaging‐guided NIR‐triggered PDT. [ABSTRACT FROM AUTHOR]

In this study, we successfully developed two novel vinylene‐linked covalent organic frameworks (COFs) using 2‐connected 3,6‐dimethylpyridazine through Knoevenagel condensation. These COFs featured finely tailored micro‐/nano‐scale pore sizes, high surface areas and stable non‐polar vinylene linkages. Finely resolved powder X‐ray diffraction patterns demonstrated highly crystalline structures with a hexagonal lattice in the AA layer stacking. The resulting one‐dimensional channels possess strong hydrogen‐bond accepting sites arising from the decorated cis‐azo/azine units with two pairs of fully exposed lone pair electrons, endowing the as‐prepared COFs with exceptional water absorption properties. The g‐DZPH‐COF exhibited successive steep water uptake steps starting from low relative pressures (P/PSTA=0.1), with the remarkable water uptake capacity of 0.26 g/g at P/PSTA=0.2 (25 °C), which is the optimal value recorded among the reported COFs. Dynamic vapour sorption measurements revealed the fast kinetics of these COFs, even in the cluster formation process. Water uptake and release cycling tests demonstrated their outstanding hydrolytic stability, durability, and adsorption–desorption retention ability. [ABSTRACT FROM AUTHOR]

Fluorescence sensing is crucial to studying biological processes and diagnosing diseases, especially in the second near‐infrared (NIR‐II) window with reduced background signals. However, it's still a great challenge to construct "off‐on" sensors when the sensing wavelength extends into the NIR‐II region to obtain higher imaging contrast, mainly due to the difficult synthesis of spectral overlapped quencher. Here, we present a new fluorescence quenching strategy, which utilizes steric hindrance quencher (SHQ) to tune the molecular packing state of fluorophores and suppress the emission signal. Density functional theory (DFT) calculations further reveal that large SHQs can competitively pack with fluorophores and prevent their self‐aggregation. Based on this quenching mechanism, a novel activatable "off‐on" sensing method is achieved via bio‐analyte responsive invalidation of SHQ, namely the Steric Hindrance Invalidation geNerated Emission (SHINE) strategy. As a proof of concept, the ClO−‐sensitive SHQ lead to the bright NIR‐II signal release in epileptic mouse hippocampus under the skull and high photon scattering brain tissue, providing the real‐time visualization of ClO− generation process in living epileptic mice. [ABSTRACT FROM AUTHOR]

Cephalotaxus diterpenoids are attractive natural products with intriguing molecular frameworks and promising biological features. As a structurally unusual member, (−)‐cephalotanin B possesses an extraordinarily congested heptacyclic skeleton, three lactone units, and nine consecutive stereocenters. Herein, we report an enantioselective total synthesis of (−)‐cephalotanin B based on a divergent asymmetric Michael addition reaction, a novel Pauson–Khand/deacyloxylation process discovered in the development of a second‐generation stereoselective Pauson–Khand reaction protocol, and an epoxide‐opening/elimination/dual‐lactonization cascade to construct the challenging propeller‐shaped A–B–C ring system as key transformations. [ABSTRACT FROM AUTHOR]

The McMurry coupling is a facile, gentle and low‐cost chemical reaction for synthesizing. Here, for the first time, we employed the McMurry coupling reaction to prepare π‐conjugated anion exchange membranes (AEMs). The inter‐chain π‐π stacking between adjacent benzene rings induces directional self‐assembly aggregation and enables highly ordered ion‐conductive channels. The resulting structure was characterized through UV/VIS spectrum, X‐ray diffraction (XRD) pattern, small‐angle X‐ray scattering (SAXS), transmission electron microscopy (TEM) and density functional theory (DFT) calculations, leading to high OH− conductivity of 135.5 mS cm−1 at 80 °C. Furthermore, the double bonds in the π‐conjugated system also trigger in situ self‐crosslinking of the AEMs to enhance dimensional and alkaline stability. Benefiting from this advantage, the as‐obtained Cr‐QPPV‐2.51 AEM exhibits superior alkaline stability (95 % conductivity retention after 3000 hrs in 1 M KOH at 80 °C) and high mechanical strength of 34.8 MPa. Moreover, the fuel cell using Cr‐QPPV‐2.51 shows a maximum peak power density of 1.27 W cm−2 at 80 °C. [ABSTRACT FROM AUTHOR]

Aqueous lead sulfide (PbS) quantum dots (QDs) synthesized by traditional methods are unstable, so that they are usually coated with cadmium sulfide (CdS) to prevent oxidation, which are complicated and not satisfactory for mass production. Here, stable ternary Pb1−xCdxS QDs were synthesized by in situ coprecipitation of Pb4−nCdnO4 bimetallic clusters in an aqueous solution, which possess a uniform size of 4.0±0.2 nm and the second near‐infrared (NIR‐II) emission at 1100 nm with photoluminescence quantum yield (PLQY) as high as 17.72 %. Stored at 4 °C and in colloidal form, the PLQY of Pb1−xCdxS QDs remained at 90.9 % of the initial value after 15 days, while stored as powder, the spectra did not change after 5 months. The high PLQY and good water compatibility of Pb1−xCdxS QDs provide a good performance in vivo vasculature imaging and lymphatic system imaging at a very low power density (10 mW cm−2) in the NIR‐II window. [ABSTRACT FROM AUTHOR]

Peroxynitrite (ONOO−) plays a critical role in Alzheimer's disease (AD). To reveal the ONOO− influx in AD brains, an activatable activity‐based fluorescence probe Rd‐DPA3 was designed by a structure‐modulated strategy. Taking advantage of ONOO−‐initiated two‐step cascade reactions of a novel chemical trigger, Rd‐DPA3 specifically responds to ONOO− in 0.3 mM of other reactive oxygen species (ROS) and varied proteins, and gives an intensive fluorescence enhancement (F/F0=50). Moreover, with its mitochondria‐targeting ability, Rd‐DPA3 can be used to efficiently monitor the alternations of intracellular ONOO− levels in cerebral cells during oxidative stress. Significantly, due to NIR emission and good blood–brain barrier (BBB) crossing ability, Rd‐DPA3 is suitable for in vivo imaging of cerebral ONOO− influx and illustrating an age‐dependent accumulation of ONOO− in AD mice brains. [ABSTRACT FROM AUTHOR]

Embedding heteroatoms into the main backbones of polymeric materials has become an efficient tool for tailoring their structures and improving their properties. However, owing to comparatively harsh heteroatom‐doping conditions, this has rarely been explored in covalent organic frameworks (COFs). Herein, upon aldol condensation of a trimethyl‐substituted pyrylium salt with a tritopic aromatic aldehyde, a two‐dimensional oxonium‐embedded COF with vinylene linkages was achieved, which was further converted to a neutral pyridine‐cored COF by in situ replacement of oxonium ions with nitrogen atoms under ammonia treatment. The two heteroatom‐embedded COFs are conceptually isoelectronic with each other, featuring similar geometric structures but different electronic structures, rendering them capable of catalyzing the visible‐light‐promoted multi‐component synthesis of tri‐substituted pyridine derivatives with good recyclability. [ABSTRACT FROM AUTHOR]

Early detection of kidney disease is of vital importance due to its current prevalence worldwide. Fluorescence imaging, especially in the second near‐infrared window (NIR‐II) has been regarded as a promising technique for the early diagnosis of kidney disease due to the superior resolution and sensitivity. However, the reported NIR‐II organic renal‐clearable probes are hampered by their low brightness (ϵmaxΦf>1000 nm<10 M−1 cm−1) and limited blood circulation time (t1/2<2 h), which impede the targeted imaging performance. Herein, we develop the aza‐boron‐dipyrromethene (aza‐BODIPY) brush macromolecular probes (Fudan BDIPY Probes (FBP 912)) with high brightness (ϵmaxΦf>1000 nm≈60 M−1 cm−1), which is about 10‐fold higher than that of previously reported NIR‐II renal‐clearable organic probes. FBP 912 exhibits an average diameter of ≈4 nm and high renal clearance efficiency (≈65 % excretion through the kidney within 12 h), showing superior performance for non‐invasively diagnosis of renal ischemia‐reperfusion injury (RIR) earlier than clinical serum‐based protocols. Additionally, the high molecular weight polymer brush enables FBP 912 with prolonged circulation time (t1/2≈6.1 h) and higher brightness than traditional PEGylated renal‐clearable control fluorophores (t1/2<2 h), facilitating for 4T1 tumor passive targeted imaging and renal cell carcinoma active targeted imaging with higher signal‐to‐noise ratio and extended retention time. [ABSTRACT FROM AUTHOR]

Organic dyes emitting in the second near‐infrared (NIR‐II, 900–1700 nm) window, with high molar extinction coefficients (MEC) and quantum yields (QY) in aqueous, are essential for in vivo bioimaging and biosensing. In this work, we developed a dibodipy‐based aggregation‐induced emission (AIE) fluorescent probe, THPP, to meet this aim. THPP exhibits a high MEC and has intensified absorption and emission in J‐aggregated state, which significantly enhance the fluorescence intensity (≈55 folds) and extend the maximal absorption/emission wavelengths to 970/1010 nm in NIR‐II region. Based on the bright THPP, imaging with a high frame rate (34 frames per second) at a deep "valid penetration depth" up to 6 mm can be achieved. This enabled simultaneous and dynamic imaging of vasculatures and deep tissues. Besides, we succeeded in monitoring the respiratory rate of acute‐lung‐injury mice and tracing the collateral circulation process with a high frame rate. [ABSTRACT FROM AUTHOR]