@article {46413,
	title = {Covalent self-assembly in two dimensions: connecting covalent organic framework nanospheres into crystalline and porous thin films},
	journal = {Journal of the American Chemical Society},
	volume = {141},
	year = {2019},
	month = {DEC },
	pages = {20379},
	type = {Article},
	chapter = {20371},
	abstract = {<p>Insolubility of covalent organic frameworks (COFs) in organic solvents is one of the major obstacles for the potential application of these extended networks such as drug delivery, sensing, optoelectronics, and semiconductor device fabrication. The present work proposes a unique way to make uniform, solution-processable, crystalline, and porous COF nanospheres directly from the homogeneous solution of amine and aldehyde via spatial and temporal control of the nucleation and growth. This strategy of direct nucleation simultaneously showcases the caliber to tune the size of the COF nanospheres from 25 to 570 nm. We have also demonstrated the concept of mesoscale covalent self-assembly of those solution-processable COF nanospheres in the liquid-liquid interface (DCM-water bilayer) for the very first time, transmuting them into self-standing COF thin films with long-range ordered arrangements in two dimensions. The crystalline and porous (with TpAzo showing highest S-BET of 1932 m(2) g(-1)) free-standing COF thin films could be fabricated in a wide range of thicknesses from as low as 21 nm to as high as 630 nm. Both beta-ketoenamine (TpAzo, TpDPP) and imine (TpOMeAzo, TpOMeDPP) linked COF thin films have been synthesized via mesoscale covalent self-assembly of the solution-processable COF nanospheres illustrating the generality of this eloquent methodology. Further, the solution processability has been tested and utilized to cast COF thin films uniformly in the inner and outer surface of an alumina hollow fiber membrane. The COF thin film-alumina hollow fiber membrane composites have showcased promising selective molecular separation of He and O-2, He and CO2, and He and N-2.</p>
},
	issn = {0002-7863},
	doi = {10.1021/jacs.9b10788},
	author = {Sasmal, Himadri Sekhar and Halder, Arjun and Kunjattu, Shebeeb and Dey, Kaushik and Nadol, Athulya and Ajithkumar, Thalasseril G. and Bedadur, Prachiti Ravindra and Banerjee, Rahul}
}
@article {48833,
	title = {Covalent organic framework thin-film photodetectors from solution-processable porous nanospheres},
	journal = {Journal of the American Chemical Society},
	volume = {145},
	year = {2023},
	month = {JAN},
	pages = {1649-1659},
	type = {Article},
	abstract = {<p>
	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.</p>
},
	issn = {0002-7863},
	doi = {10.1021/jacs.2c09838},
	author = {Bag, Saikat and Sasmal, Himadri Sekhar and Chaudhary, Sonu Pratap and Dey, Kaushik and Blaette, Dominic and Guntermann, Roman and Zhang, Yingying and Poloz, Miroslav and Kuc, Agnieszka and Shelke, Ankita and Vijayaraghavan, Ratheesh K. and Ajithkumar, Thalasseril G. and Bhattacharyya, Sayan and Heine, Thomas and Bein, Thomas and Banerjee, Rahul}
}
