Crystallization of Dimensional Isomers in Covalent Organic Frameworks.

Dimensional isomers, defined in reticular chemistry as frameworks consisting of identical molecular building blocks but extended in two or three dimensions (2D or 3D), are an important type of framework isomers that have never been isolated. Herein, we report the crystallization of dimensional isomers in covalent organic frameworks (COFs) for the first time. By polymerization of the same molecular building blocks at different temperatures, both 2D and 3D COFs were successfully constructed due to the temperature-induced conformational changes of precursors from planar to tetrahedral. In addition, the non-fluorescent 2D COF can be gradually converted into the fluorescent 3D COF by increasing the temperature under solvothermal conditions. Therefore, it is reasonable to crystallize the dimensional isomers of reticular materials by controlling the conformation of molecular building blocks, and more examples can be expected. Since the obtained dimensional isomers show different properties and functions, this work will definitely motivate us to design reticular materials for target applications in the future.

Long non-coding RNA ANRIL interacts with microRNA-34a and microRNA-125a, and they all correlate with disease risk and severity of Parkinson's disease.

BACKGROUND: This study aimed to investigate the correlation of long non-coding RNA antisense non-coding RNA in the INK4 locus (lncRNA ANRIL) and its target microRNAs (microRNA-34a (miR-34a) and microRNA-125a (miR-125a)) with disease risk and severity of Parkinson's disease (PD). METHODS: Seventy-eight PD patients and 78 age-/gender-matched controls were consecutively enrolled. Their peripheral blood mononuclear cell samples were collected and proposed for the reverse-transcription quantitative polymerase chain reaction to complete lncRNA ANRIL, miR-34a, and miR-125a measurements. RESULTS: LncRNA ANRIL was upregulated, while miR-34a and miR-125a were downregulated in PD patients compared to controls (all p < 0.001). Further, they all showed certain values for PD risk identification by ROC curve analyses, among which lncRNA ANRIL showed the highest AUC (AUC: 0.879, 95% CI: 0.824-0.934). Furthermore, lncRNA ANRIL negatively correlated with miR-34a (p = 0.016) and miR-125a (p = 0.005) in PD patients, but not in controls. In addition, lncRNA ANRIL was observed to positively associate with UPDRS-I score (p = 0.029), UPDRS-III score (p = 0.006), and UPDRS-IV score (p = 0.033), while negatively correlated with MMSE score (p = 0.003). These associations were less distinct as to miR-34a and miR-125a. CONCLUSION: LncRNA ANRIL interacts with miR-34a and miR-125a in PD patients, and they all correlate with disease risk and severity of PD.

A Crystalline Three-Dimensional Covalent Organic Framework with Flexible Building Blocks.

The construction of three-dimensional covalent organic frameworks (3D COFs) has proven to be very challenging, as their synthetic driving force mainly comes from the formation of covalent bonds. To facilitate the synthesis, rigid building blocks are always the first choice for designing 3D COFs. In principle, it should be very appealing to construct 3D COFs from flexible building blocks, but there are some obstacles blocking the development of such systems, especially for the designed synthesis and structure determination. Herein, we reported a novel highly crystalline 3D COF (FCOF-5) with flexible C-O single bonds in the building block backbone. By merging 17 continuous rotation electron diffraction data sets, we successfully determined the crystal structure of FCOF-5 to be a 6-fold interpenetrated pts topology. Interestingly, FCOF-5 is flexible and can undergo reversible expansion/contraction upon vapor adsorption/desorption, indicating a breathing motion. Moreover, a smart soft polymer composite film with FCOF-5 was fabricated, which can show a reversible vapor-triggered shape transformation. Therefore, 3D COFs constructed from flexible building blocks can exhibit interesting breathing behavior, and finally, a totally new type of soft porous crystals made of pure organic framework was announced.

Three-Dimensional Covalent Organic Frameworks: From Topology Design to Applications.

ConspectusCovalent organic frameworks (COFs) represent a novel type of crystalline porous polymers with potential applications in many areas. Considering their covalent connectivity in different dimensions, COFs are classified as two-dimensional (2D) layered structures or three-dimensional (3D) networks. In particular, 3D COFs have gained increasing attention recently because of their remarkably large surface areas (>5000 m2/g), hierarchical nanopores and numerous open sites. However, it has been proven to be a major challenge to construct 3D COFs, as the main driving force for their synthesis comes from the formation of covalent bonds. In addition, there are several stones on the roads blocking the development of 3D COFs. First, the successful topology design strategies of 3D COFs have been limited to [4 + 2] or [4 + 3] condensation reactions of the tetrahedral molecules with linear or triangular building blocks in the first decade, which led to only three available topologies (ctn, bor, and dia) and strongly restricted the incorporation of some important functional units. Next, as it is very challenging to obtain large-size single crystals of 3D COFs and the same building blocks may yield many possible structures that are quite difficult to identify from simulations, their structure determination has been considered a major issue. Last, the building blocks utilized to synthesize 3D COFs are very limited, which further affects their functionalization and applications. Therefore, since it was first announced in 2007, research studies regarding 3D COFs have been underexplored for many years, and very few examples have been reported.To confront these obstacles in 3D COFs, we started contributing to this field in 2016. Considering that many interesting quadrilateral molecules (e.g., pyrene and porphyrin) cannot be easily derivatized into linear or triangular motifs, we developed a novel topology design strategy to construct 3D COFs via [4 + 4] condensation reactions of tetrahedral and quadrilateral building blocks. After many trials, we found that this is a general synthetic strategy to build 3D COFs with the new pts topology. In addition, we explored the structure determination of polycrystalline 3D COFs prepared by our developed strategy via a 3D electron diffraction technique. Moreover, we expanded the toolbox of molecular building blocks for creating 3D COFs and successfully demonstrated the functionalization of 3D COFs with characteristic properties and applications. In this Account, we summarize our above ongoing research contributions, including (i) a novel topology design strategy for the synthesis of 3D COFs; (ii) attempts to determine the crystal structure of polycrystalline 3D COFs with atomic resolution; and (iii) the diversification of building blocks and applications of functionalized 3D COFs. Overall, our studies not only offer a new paradigm of expansion in the topology design strategy and building block families of 3D COFs, but also provide an idea of future opportunities for relevant researchers in this field.

Isostructural Three-Dimensional Covalent Organic Frameworks.

Herein, we reported the designed synthesis of three isostructural three-dimensional covalent organic frameworks (3D COFs) with -H, -Me, or -F substituents, which have similar crystallinity and topology. Their crystal structures were determined by continuous rotation electron diffraction (cRED), and all three 3D COFs were found to adopt a fivefold interpenetrated pts topology. More importantly, the resolution of these cRED datasets reached up to 0.9-1.0 Å, enabling the localization of all non-hydrogen atomic positions in a COF framework directly by 3D ED techniques for the first time. In addition, the precise control of the pore environments through the use of different functional groups led to different selectivities for CO2 over N2 . We have thus confirmed that polycrystalline COFs can be definitely studied to the atomic level as other materials, and this study should also inspire the design and synthesis of 3D COFs with tailored pore environments for interesting applications.

Designed Synthesis of a 2D Porphyrin-Based sp2 Carbon-Conjugated Covalent Organic Framework for Heterogeneous Photocatalysis.

The construction of stable covalent organic frameworks (COFs) for various applications is highly desirable. Herein, we report the synthesis of a novel two-dimensional (2D) porphyrin-based sp2 carbon-conjugated COF (Por-sp2 c-COF), which adopts an eclipsed AA stacking structure with a Brunauer-Emmett-Teller surface area of 689 m2 g-1 . Owing to the C=C linkages, Por-sp2 c-COF shows a high chemical stability under various conditions, even under harsh conditions such as 9 m HCl and 9 m NaOH solutions. Interestingly, Por-sp2 c-COF can be used as a metal-free heterogeneous photocatalyst for the visible-light-induced aerobic oxidation of amines to imines. More importantly, in comparison to imine-linked Por-COF, the inherent structure of Por-sp2 c-COF equips it with several advantages as a photocatalyst, including reusability and high photocatalytic performance. This clearly demonstrates that sp2 carbon-linked 2D COFs can provide an interesting platform for heterogeneous photocatalysis.

An AIEgen-based 3D covalent organic framework for white light-emitting diodes.

The design and synthesis of three-dimensional covalent organic frameworks (3D COFs) have still been considered as a big challenge. Here we report the design and synthesis of an AIEgen-based 3D COF (3D-TPE-COF), with a high surface area (1084 m2 g-1). According to powder X-ray diffraction and continuous rotation electron diffraction analyses, 3D-TPE-COF is identified to adopt a seven-fold interpenetrated pts topology. Interestingly, 3D-TPE-COF emits yellow fluorescence upon excitation, with a photoluminescence quantum yield of 20%. Moreover, by simply coating 3D-TPE-COF onto a commercial blue light-emitting diode (LED), a prototype white LED (WLED) under continuously driving without degradation for 1200 h was demonstrated. The present work suggests the possibility of using COF materials for stable WLEDs, which will greatly inspire us to design and synthesize fluorescent 3D COFs and facilitate the development of COF-based WLEDs in future.

Transplanted human neural precursor cells integrate into the host neural circuit and ameliorate neurological deficits in a mouse model of traumatic brain injury.

Traumatic brain injury (TBI) is to date one of the major critical conditions causing death and disability worldwide. Exogenous neural stem/precursor cells (NSCs/NPCs) hold great promise for improving neurological dysfunction, but their functional properties in vivo remain unknown. Human neural precursor cells (hNPCs) carrying one fluorescent reporter gene (DsRed) can be observed directly in vivo using two-photon laser-scanning microscope. Therefore, we evaluated the neural integration and potential therapeutic effect of hNPCs on mice with TBI. Behavioral tests were performed by rotarod task and Morris Water Maze task. Neural integration was detected by fluorometric Ca2+ imaging and nerve tracing. We found that motor and cognition functions were significantly improved in mice with hNPCs injection compared to mice with vehicle treatment, and hNPCs integrated into the host circuit and differentiated toward neuronal lineage. Our study provided reliable evidence for further hNPCs transplantation in clinical practice.

3D Porphyrin-Based Covalent Organic Frameworks.

The design and synthesis of three-dimensional covalent organic frameworks (3D COFs) bearing photoelectric units have been considered as a big challenge. Herein, for the first time, we reported the targeted synthesis of two 3D porphyrin-based COFs (3D-Por-COF and 3D-CuPor-COF), starting from tetrahedral (3D-Td) and square (2D-C4) building blocks connected through [4 + 4] imine condensation reactions. On the basis of structural characterizations, 3D-Por-COF and 3D-CuPor-COF are microporous materials with high surface areas, and are proposed to adopt a 2-fold interpenetrated pts topology with Pmc21 space group. Interestingly, both 3D COFs are photosensitive and can be used as heterogeneous catalyst for generating singlet oxygen under photoirradiation. However, 3D-Por-COF shows enhanced photocatalytic activity compared with 3D-CuPor-COF, indicating the properties of 3D porphyrin-based COFs can be tuned by metalation of porphyrin rings. The results reported here will greatly inspire us to design and synthesize 3D COFs bearing other metalloporphyrins for interesting applications (e.g., catalysis) in the future.

A Pyrene-Based, Fluorescent Three-Dimensional Covalent Organic Framework.

The targeted synthesis of 3D COFs has been considered challenging, especially adopting new topologies and bearing photoelectric units. Herein, for the first time, we report the synthesis and characterization of a novel 3D pyrene-based COF (3D-Py-COF), by selectively choosing the geometry of the precursors and the connection patterns. Based on X-ray diffraction measurement and detailed simulations, 3D-Py-COF is proposed to adopt a two-fold interpenetrated pts topology, which has never been reported before. In addition, 3D-Py-COF has a narrow pore size distribution and high surface area and also features selective absorption of CO2 over N2. Interestingly, due to the existence of isolated pyrene units in the 3D framework, 3D-Py-COF is the first fluorescent 3D COF and can be used in explosive detection. Our results not only show it is possible to rationally design and synthesize 3D COFs with other topologies but also demonstrate that the incorporation of photoelectric units into 3D COFs can allow the resulting materials with interesting properties.