@article { ISI:000365205000004, title = {Pore surface engineering in porous, chemically stable covalent organic frameworks for water adsorption}, journal = {Journal of Materials Chemistry A}, volume = {3}, number = {47}, year = {2015}, month = {NOV}, pages = {23664-23669}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Herein, we have explored the possibility of a class of covalent organic frameworks (COFs) as water adsorbing materials. We have selected, synthesized 12 chemically stable functionalized Schiff base COFs and thoroughly studied their water uptake behaviour. Further, a deep understanding was developed with these COFs towards the effects of condensation pressure of water and hydrophilic/hydrophobic groups present in the COF pores on water absorption capacity and ultimately, their recyclability. Among all reported COFs, TpPa-1 shows the highest water uptake of 30 wt\% (368 cm(3) g(-1); 17 mmol g(-1)) at P/P-0 = 0.3, which is also comparable with the recently reported carbon materials and few well known MOFs. This study also reveals that the overall water uptake of COFs can be tuned systematically based on chemical functionality and pore size in a wider window of relative pressures.

}, issn = {2050-7488}, doi = {10.1039/c5ta07998e}, author = {Biswal, Bishnu P. and Kandambeth, Sharath and Chandra, Suman and Shinde, Digambar Balaji and Bera, Saibal and Karak, Suvendu and Garai, Bikash and Kharul, Ulhas K. and Banerjee, Rahul} } @article {44399, title = {Porosity prediction through hydrogen bonding in covalent organic frameworks}, journal = {Journal of the American Chemical Society}, volume = {140}, year = {2018}, month = {APR}, pages = {5138-5145}, abstract = {Easy and bulk-scale syntheses of two-dimensional (2D) covalent organic frameworks (COFs) represent an enduring challenge in material science. Concomitantly, the most critical aspect is to precisely control the porosity and crystallinity of these robust structures. Disparate complementary approaches such as solvothermal synthesis have emerged recently and are fueled in part by the usage of different modulators and acids that have enriched the COF library. Yet, the fundamental understanding of the integral processes of 2D COF assembly, induding their growth from nucleating sites and the origin of periodicity, is an intriguing chemical question that needs to be answered. To address these cardinal questions, a green and easy-to-perform approach of COF formation has been delineated involving acid-diamine salt precursors. The role of hydrogen bonding [d(av)(N-amine-H center dot center dot center dot O-acid); d(av) signifies the average N-amine-H center dot center dot center dot O-acid distances, i.e., the average distance from the H atom of the amine to the O atom of the acid] present in the acid-diamine salts in improving the COFs{\textquoteright} crystallinity and porosity has further been decoded by thorough crystallographic analyses of the salt molecules. What is particularly noteworthy is that we have established the hydrogen-bonding distances d(av)(N-amine-H center dot center dot center dot O-acid) in the acid-diamine salts that are pivotal in maintaining the reversibility of the reaction, which mainly facilitates highly crystalline and porous COF formation. Moreover, this reactant-structure to the product-quality relationship has further been utilized for the synthesis of highly crystalline and porous COFs that are unattainable by other synthetic means.}, doi = {10.1021/jacs.7b13558}, author = {Karak, Suvendu and Kumar, Sushil and Pachfule, Pradip and Banerjee, Rahul} } @article {46162, title = {Porosity switching in polymorphic porous organic cages with exceptional chemical stability}, journal = {Angewandte Chemie-International Edition}, volume = {58}, year = {2019}, month = {MAR}, pages = {4243-4247}, type = {Article}, abstract = {

Porous solids that can be switched between different forms with distinct physical properties are appealing candidates for separation, catalysis, and host-guest chemistry. In this regard, porous organic cages (POCs) are of profound interest because of their solution-state accessibility. However, the application of POCs is limited by poor chemical stability. Synthesis of an exceptionally stable imine-linked (4+6) porous organic cage (TpOMe-CDA) is reported using 2,4,6-trimethoxy-1,3,5-triformyl benzene (TpOMe) as a precursor aldehyde. Introduction of the -OMe functional group to the aldehyde creates significant steric and hydrophobic characteristics in the environment around the imine bonds that protects the cage molecules from hydrolysis in the presence of acids or bases. The electronic effect of the -OMe group also plays an important role in enhancing the stability of the reported POCs. As a consequence, TpOMe-CDA reveals exceptional chemical stability in neutral, acidic and basic conditions, even in 12m NaOH. Interestingly, TpOMe-CDA exists in three different porous and non-porous polymorphic forms (, , and ) with respect to differences in crystallographic packing and the orientation of the flexible methoxy groups. All of the polymorphs retain their crystallinity even after treatment with acids and bases. All the polymorphs of TpOMe-CDA differ significantly in their properties as well as morphology and could be reversibly switched in the presence of an external stimulus.

}, keywords = {chemical stability, Morphology, organic cages, polymorphism, porosity switching}, issn = {1433-7851}, doi = {10.1002/anie.201813773}, author = {Bera, Saibal and Dey, Kaushik and Pal, Tapan K. and Halder, Arjun and Tothadi, Srinu and Karak, Suvendu and Addicoat, Matthew and Banerjee, Rahul} } @article {48209, title = {Porous covalent organic nanotubes and their assembly in loops and toroids}, journal = {Nature Chemistry}, volume = {14}, year = {2022}, month = {MAY}, pages = {507+}, type = {Article}, abstract = {

Carbon nanotubes, and synthetic organic nanotubes more generally, have in recent decades been widely explored for application in electronic devices, energy storage, catalysis and biosensors. Despite noteworthy progress made in the synthesis of nanotubular architectures with well-defined lengths and diameters, purely covalently bonded organic nanotubes have remained somewhat challenging to prepare. Here we report the synthesis of covalently bonded porous organic nanotubes (CONTs) by Schiff base reaction between a tetratopic amine-functionalized triptycene and a linear dialdehyde. The spatial orientation of the functional groups promotes the growth of the framework in one dimension, and the strong covalent bonds between carbon, nitrogen and oxygen impart the resulting CONTs with high thermal and chemical stability. Upon ultrasonication, the CONTs form intertwined structures that go on to coil and form toroidal superstructures. Computational studies give some insight into the effect of the solvent in this assembly process.

}, issn = {1755-4330}, doi = {10.1038/s41557-022-00908-1}, author = {Koner, Kalipada and Karak, Shayan and Kandambeth, Sharath and Karak, Suvendu and Thomas, Neethu and Leanza, Luigi and Perego, Claudio and Pesce, Luca and Capelli, Riccardo and Moun, Monika and Bhakar, Monika and Ajithkumar, Thalasseril G. and Pavan, Giovanni M. and Banerjee, Rahul} }