The rapid development in synthesis methodology and applications for covalent organic frameworks (COFs) has been witnessed in recent years. However, the synthesis of highly stable functional COFs still remains a great challenge. Herein twodimensional polyimide-linked phthalocyanine COFs (denoted as CoPc-PI-COF-1 and CoPc-PI-COF-2) have been devised and prepared through the solvothermal reaction of the tetraanhydrides of 2, 3,9,10,16,17,23, with 1,4phenylenediamine and 4,4′-biphenyldiamine, respectively. The resultant CoPc-PI-COFs with a four-connected sql net exhibit AA stacking configurations according to powder X-ray diffraction studies, showing permanent porosity, thermal stability above 300 °C, and excellent resistance to a 12 M HCl aqueous solution for 20 days. Current−voltage curves reveal the conductivity of CoPc-PI-COF-1 and CoPc-PI-COF-2 with the value of 3.7 × 10 −3 and 1.6 × 10 −3 S m −1 , respectively. Due to the same Co(II) electroactive sites together with similar permanent porosity and CO 2 adsorption capacity for CoPc-PI-COFs, the cathodes made up of COFs and carbon black display a similar CO 2 -to-CO Faradaic efficiency of 87−97% at applied potentials between −0.60 and −0.90 V (vs RHE) in 0.5 M KHCO 3 solution. However, in comparison with the CoPc-PI-COF-2&carbon black electrode, the CoPc-PI-COF-1 counterpart provides a larger current density (j CO ) of −21.2 mA cm −2 at −0.90 V associated with its higher conductivity. This cathode also has a high turnover number and turnover frequency, amounting to 277 000 and 2.2 s −1 at −0.70 V during 40 h of measurement. The present result clearly discloses the great potential of 2D porous crystalline solids in electrocatalysis.
Covalent organic frameworks (COFs) are gaining increasing attention as renewable cathode materials for Liion batteries. However, COF electrodes reported so far still exhibit unsatisfying capacity due to their limited active site density and insufficient utilization. Herein, a new two-dimensional polyimide-linked COF, HATN-AQ-COF with multiple redox-active sites for storing Li + ions, was designed and fabricated from a new module of 2,3,8,9,14,15hexacarboxyl hexaazatrinaphthalene trianhydrides with a 2,6-diaminoanthraquinone linker. HATN-AQ-COF possessing excellent stability, good conductivity, and a large pore size of 3.8 nm enables the stable and fast ion transport. This, in combination with the abundant redox active sites, results in a high reversible capacity of 319 mAh g À 1 at 0.5 C (1 C = 358 mA g À 1 ) for the HATN-AQ-COF electrode with a high active site utilization of 89 % and good cycle performance, representing one of the best performances among the reported COF electrodes.
Artificial photosynthesis of H2O2 from O2 reduction provides an energy-saving, safe, and green approach. However, it is still critical to develop highly active and selective 2e– oxygen reduction reaction photocatalysts for efficient H2O2 production owing to the unsatisfactory photosynthesis productivity. Herein, two new two-dimensional piperazine-linked CoPc-based covalent organic frameworks (COFs), namely, CoPc-BTM-COF and CoPc-DAB-COF, were afforded from the nucleophilic substitution reaction of hexadecafluorophthalocyaninato cobalt(II) (CoPcF16) with 1,2,4,5-benzenetetramine (BTM) or 3,3′-diaminobenzidine (DAB). Powder X-ray diffraction analysis in combination with electron microscopy and a series of spectroscopic technologies reveals their crystalline porous framework with a fully conjugated structure and eclipsed π-stacking model. Ultraviolet–visible diffuse reflectance absorption spectra unveil their excellent light absorption capacity in a wide range of 400–1000 nm. This, together with their enhanced photo-induced charge separation and transport efficiency as disclosed by photocurrent response and photoluminescence measurements, endows the as-prepared piperazine-linked CoPc-based COFs with superior photocatalytic activity toward O2-to-H2O2 conversion under visible-light irradiation (λ > 400 nm). In particular, CoPc-BTM-COF exhibits a record-high H2O2 yield of 2096 μmol h–1 g–1 among the COF-based photocatalysts and an impressive apparent quantum yield of 7.2% at 630 nm. The present result should be helpful for fabricating high-performance and low-cost photocatalysts for visible-light-driven H2O2 photosynthesis.
Developing conjugated three-dimensional (3D) covalent organic frameworks (COFs) still remains an extremely difficult task due to the lack of enough conjugated 3D building blocks. Herein, condensation between an 8-connected pentiptycene-based D 2h building block (DMOPTP) and 4-connected square-planar linkers affords two 3D COFs (named 3D-scu-COF-1 and 3D-scu-COF-2). A combination of the 3D homoaromatic conjugated structure of the former building block with the 2D conjugated structure of the latter linking units enables the π-electron delocalization over the whole frameworks of both COFs, endowing them with excellent conductivities of 3.2−3.5 × 10 −5 S cm −1 . In particular, the 3D rigid quadrangular prism shape of DMOPTP guides the formation of a twofold interpenetrated scu 3D topology and high-connected permanent porosity with a large Brunauer−Emmett−Teller (BET) surface area of 2340 and 1602 m 2 g −1 for 3D-scu-COF-1 and 3D-scu-COF-2, respectively, ensuring effective small molecule storage and mass transport characteristics. This, in combination with their good charge transport properties, renders them promising sulfur host materials for lithium−sulfur batteries (LSBs) with high capacities (1035−1155 mA h g −1 at 0.2 C, 1 C = 1675 mA g −1 ), excellent rate capabilities (713−757 mA h g −1 at 5.0 C), and superior cycling stability (71−83% capacity retention at 2.0 C after 500 cycles), surpassing the most of organic LSB cathodes reported thus far.
Photothermal therapy in the second near-infrared window (NIR-II, 1000-1700 nm) exhibits a significant advantage over the first near-infrared window (NIR-I, 650-950 nm) in terms of both maximum permissible exposure (MPE) and penetration depth. However, the thus far reported NIR-II photothermal agents (PTAs) have been focused just on inorganic semiconducting and organic polymeric semiconducting nanoparticles. Herein a novel cruciform phthalocyanine pentad was designed, synthesized, and characterized for the first time. The water-soluble nanoparticles (Zn 4 -H 2 Pc/DP NPs) assembled from this single molecular material with the help of DSPE-PEG 2000 -OCH 3 exhibit characteristic absorption in the NIR-II region at 1064 nm with a large extinction coefficient of 52 L g À1 cm À1 , high photothermal conversion efficiency of 58.3%, and intense photoacoustic signal. Moreover, both in vitro and in vivo studies reveal the good biocompatibility and notable tumor ablation ability of Zn 4 -H 2 Pc/DP NPs under 1064 nm laser irradiation. Theoretical density functional theory calculations interpret the two-dimensional compressional wave energy-dissipation pathway over the broad saddle curved framework of the cruciform conjugated phthalocyanine pentad, rationalizing the efficient photothermal properties of corresponding Zn 4 -H 2 Pc/DP NPs in the NIR-II window. Scheme 1 (a) Illustration of Zn 4 -H 2 Pc/DP NP fabrication for photothermal therapy and photoacoustic imaging. (b) UV-vis-NIR absorption and fluorescence emission spectra of Zn 4 -H 2 [Pc(OC 12 H 17 ) 24 ] (1) in CH 2 Cl 2 and Zn 4 -H 2 Pc/DP NPs in water, respectively. (c) DLS profile, (d) TEM, and (e) AFM images of Zn 4 -H 2 Pc/DP NPs. This journal isFig. 2 (a) Molecular structure of Zn 4 -H 2 [Pc(OC 12 H 17 ) 24 ] (1) optimized on the basis of DFT calculations with all the hydrogen atoms and substituents omitted for clarity. (b) Non-covalent interactions between the solvent molecules and the peripheral -OC 12 H 17 groups. (c) The occupied frontier orbitals of 1 coupled by corresponding orbitals of the peripheral ZnPc* unit and the central H 2 Pc* core. (d) Schematic Jablonski diagram representing different energy transfer pathways. This journal is ., 2017, 8, 7457-7463.Fig. 4 (a) Temperature elevation of the tumor region in MCF-7 tumor-bearing mice under 1064 nm laser irradiation at a power density of 0.6 W cm À2 for 10 min with or without the assistance of intratumoral injection of Zn 4 -H 2 Pc/DP NPs. (b) Corresponding IR thermal images of mice under irradiation at varied time intervals (0, 0.5, 1, 3, and 10 min). (c) Tumor growth curves and (d) body-weight curves of mice in control and NP groups after treatment (n ¼ 5). (e) Digital photos of mice before and after treatment at varied time intervals (0, 1, 3, 7, 12, and 20 day).This journal is
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