02242nas a2200241 4500008004100000022001400041245012400055210006900179260007100248300001600319490000800335520133000343100001901673700002401692700002301716700001801739700002501757700002801782700002501810700001801835700002001853856012701873 2013 eng d a0002-786300aChemically stable multilayered covalent organic nanosheets from covalent organic frameworks via mechanical delamination0 aChemically stable multilayered covalent organic nanosheets from  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcNOV a17853-178610 v1353 a

A series of five thermally and chemically stable functionalized covalent organic frameworks (COFs), namely, TpPa-NO2, TpPa-F-4, TpBD-(NO2)(2), TpBD-Me-2, and TpBD-(OMe)(2) were synthesized by employing the solvothermal aldehyde-amine Schiff base condensation reaction. In order to complete the series, previously reported TpPa-1, TpPa-2, and TpBD have also been synthesized, and altogether, eight COFs were fully characterized through powder X-ray diffraction (PXRD), Fourier transform IR (FT-IR) spectroscopy, C-13 solid-state NMR spectroscopy, and thermogravimetric analysis. These COFs are crystalline, permanently porous, and stable in boiling water, acid (9 N HCl), and base (3 N NaOH). The. synthesized COFs (all eight) were successfully delaminated using a simple, safe, and environmentally friendly mechanical grinding route to transform into covalent organic nanosheets (CONs) and were well characterized via transmission electron microscopy and atomic force microscopy. Further PXRD and FT-IR analyses confirm that these CONs retain their structural integrity throughout the delamination process and also remain stable in aqueous, acidic, and basic media like the parent COFs. These exfoliated CONs have graphene-like layered morphology (delaminated layers), unlike the COFs from which they were synthesized.

1 aChandra, Suman1 aKandambeth, Sharath1 aBiswal, Bishnu, P.1 aLukose, Binit1 aKunjir, Shrikant, M.1 aChaudhary, Minakshi, V.1 aBabaRao, Ravichandar1 aHeine, Thomas1 aBanerjee, Rahul uhttp://library.ncl.res.in/content/chemically-stable-multilayered-covalent-organic-nanosheets-covalent-organic-frameworks-001914nas a2200241 4500008004100000022001400041245007500055210006900130260011000199300001400309490000600323520105000329100001701379700002301396700002401419700001801443700002001461700002601481700001801507700001901525700002001544856010801564 2015 eng d a2041-652000aChemical sensing in two dimensional porous covalent organic nanosheets0 aChemical sensing in two dimensional porous covalent organic nano aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcAPR a3931-39390 v63 a

Two new imide-based crystalline, porous, and chemically stable covalent organic frameworks (COFs) (TpBDH and TfpBDH) have been successfully synthesized employing solvothermal crystallization route. Furthermore, thin layered covalent organic nanosheets (CONs) were derived from these bulk COFs by the simple liquid phase exfoliation method. These 2D CONs showcase increased luminescence intensity compared to their bulk counterparts (COFs). Notably, TfpBDH-CONs showcase good selectivity and prominent, direct visual detection towards different nitroaromatic analytes over TpBDH-CONs. Quite interestingly, TfpBDH-CONs exhibit a superior ``turn-on'' detection capability for 2,4,6-trinitrophenol (TNP) in the solid state, but conversely, they also show a ``turn-off'' detection in the dispersion state. These findings describe a new approach towards developing an efficient, promising fluorescence chemosensor material for both visual and spectroscopic detection of nitroaromatic compounds with very low [10(-5) (M)] analyte concentrations.

1 aDas, Gobinda1 aBiswal, Bishnu, P.1 aKandambeth, Sharath1 aVenkatesh, V.1 aKaur, Gagandeep1 aAddicoat, Matthew, A.1 aHeine, Thomas1 aVerma, Sandeep1 aBanerjee, Rahul uhttp://library.ncl.res.in/content/chemical-sensing-two-dimensional-porous-covalent-organic-nanosheets-002902nas a2200325 4500008004100000022001400041245010100055210006900156260000800225300001400233490000800247520183600255100001602091700002802107700002802135700001702163700002102180700002202201700002002223700002002243700001902263700001902282700003302301700003202334700002502366700001802391700001702409700002002426856013002446 2023 eng d a0002-786300aCovalent organic framework thin-film photodetectors from solution-processable porous nanospheres0 aCovalent organic framework thinfilm photodetectors from solution cJAN a1649-16590 v1453 a

The synthesis of homogeneous covalent organic framework (COF) thin films on a desired substrate with decent crystallinity, porosity, and uniform thickness has great potential for optoelectronic applications. We have used a solution-processable sphere transmutation process to synthesize 300 +/- 20 nm uniform COF thin films on a 2 x 2 cm2 TiO2-coated fluorine-doped tin oxide (FTO) surface. This process controls the nucleation of COF crystallites and molecular morphology that helps the nanospheres to arrange periodically to form homogeneous COF thin films. We have synthesized four COF thin films (TpDPP, TpEtBt, TpTab, and TpTta) with different functional backbones. In a close agreement between the experiment and density functional theory, the TpEtBr COF film showed the lowest optical band gap (2.26 eV) and highest excited-state lifetime (8.52 ns) among all four COF films. Hence, the TpEtBr COF film can participate in efficient charge generation and separation. We constructed optoelectronic devices having a glass/FTO/TiO2/COF-film/Au architecture, which serves as a model system to study the optoelectronic charge transport properties of COF thin films under dark and illuminated conditions. Visible light with a calibrated intensity of 100 mW cm-2 was used for the excitation of COF thin films. All of the COF thin films exhibit significant photocurrent after illumination with visible light in comparison to the dark. Hence, all of the COF films behave as good photoactive substrates with minimal pinhole defects. The fabricated out-of-plane photodetector device based on the TpEtBr COF thin film exhibits high photocurrent density (2.65 +/- 0.24 mA cm-2 at 0.5 V) and hole mobility (8.15 +/- 0.64 x10-3 cm2 V-1 S-1) compared to other as synthesized films, indicating the best photoactive characteristics.

1 aBag, Saikat1 aSasmal, Himadri, Sekhar1 aChaudhary, Sonu, Pratap1 aDey, Kaushik1 aBlaette, Dominic1 aGuntermann, Roman1 aZhang, Yingying1 aPoloz, Miroslav1 aKuc, Agnieszka1 aShelke, Ankita1 aVijayaraghavan, Ratheesh, K.1 aAjithkumar, Thalasseril, G.1 aBhattacharyya, Sayan1 aHeine, Thomas1 aBein, Thomas1 aBanerjee, Rahul uhttp://library.ncl.res.in/content/covalent-organic-framework-thin-film-photodetectors-solution-processable-porous-nanospheres