@article {46326, title = {Ag nanoparticles supported on a resorcinol-phenylenediamine-based covalent organic framework for chemical fixation of CO2}, journal = {Chemistry-An Asian Journal }, year = {2019}, month = {OCT}, type = {Article; Early Access}, abstract = {

Covalent organic frameworks are a new class of crystalline organic polymers possessing a high surface area and ordered pores. Judicious selection of building blocks leads to strategic heteroatom inclusion into the COF structure. Owing to their high surface area, exceptional stability and molecular tunability, COFs are adopted for various potential applications. The heteroatoms lining in the pores of COF favor synergistic host-guest interaction to enhance a targeted property. In this report, we have synthesized a resorcinol-phenylenediamine-based COF which selectively adsorbs CO2 into its micropores (12 angstrom). The heat of adsorption value (32 kJ mol(-1)) obtained from the virial model at zero-loading of CO2 indicates its favorable interaction with the framework. Furthermore, we have anchored small-sized Ag nanoparticles (approximate to 4-5 nm) on the COF and used the composite for chemical fixation of CO2 to alkylidene cyclic carbonates by reacting with propargyl alcohols under ambient conditions. Ag@COF catalyzes the reaction selectively with an excellent yield of 90 \%. Recyclability of the catalyst has been demonstrated up to five consecutive cycles. The post-catalysis characterizations reveal the integrity of the catalyst even after five reaction cycles. This study emphasizes the ability of COF for simultaneous adsorption and chemical fixation of CO2 into corresponding cyclic carbonates.

}, keywords = {CO2 capture, covalent organic frameworks, cyclic carbonates, Propargyl alcohols, silver nanoparticles}, issn = {1861-4728}, doi = {10.1002/asia.201901157}, author = {Chakraborty, Debanjan and Shekhar, Pragalbh and Singh, Himan Dev and Kushwaha, Rinku and Vinod, C. P. and Vaidhyanathan, Ramanathan} } @article {47318, title = {Nanoporous covalent organic framework embedded with Fe/Fe3O4 nanoparticles as air-stable low-density nanomagnets}, journal = {ACS Applied Nano Materials}, volume = {3}, year = {2020}, month = {SEP }, pages = {9088-9096}, type = {Article}, abstract = {

Covalent organic frameworks (COFs) made of light atoms such as H, C, N, and O with a significant void-to-framework ratio are excellent low-density supports for nanoparticles (nPs). Their framework can be precoded with heteroatoms to ensure binding with metallic nanoclusters. With these advantages, if controlled amounts of magnetic nPs are anchored to them, they can yield low-density organic-inorganic nanomagnets. Their organic nature facilitates fusion with bulk materials such as paper/textile to enable bulk composites with well-dispersed low-density magnets, which have potential for defense and next-generation aviation applications. Herein, we have grown small Fe/Fe3O4 nPs (5-18 wt \%) inside a COF. Interestingly, 300 mg of this organic-inorganic framework material (containing 50 mg of nPs) can lift a vial of similar to 15,000 mg (300 times heavier). Also, the hydrophobic COF wraps around the Fe/Fe3O4 nanocluster retaining its room-temperature magnetic character even after 1 year, while the naked nPs lose it within a few days because of air oxidation. Bulk composites with paper and polymers have been made using this low-density Fe-COF to demonstrate their processability.

}, keywords = {air-stable nanomagnets, Covalent organic framework, Fe/Fe3O4 nanoparticles, low-density nanomagnets, magnetic rayon, nanoporous COF}, issn = {2574-0970}, doi = {10.1021/acsanm.0c01762}, author = {Kushwaha, Rinku and Kaleeswaran, Dhananjayan and Haldar, Sattwick and Chakraborty, Debanjan and Mullangi, Dinesh and Borah, Aditya and Vinod, Chathakudath P. and Murugavel, Ramaswamy and Vaidhyanathan, Ramanathan} } @article {47067, title = {Exceptional capacitance enhancement of a non-conducting COF through potential-driven chemical modulation by redox electrolyte}, journal = {Advanced Energy Materials}, volume = {11}, year = {2021}, month = {APR}, pages = {2003626}, type = {Article}, abstract = {

Capacitors are the most practical high-storage and rapid charge-release devices. The number of ions stored per unit area and their interaction strength with the electrode dictates capacitor-performance. Microporous materials provide a high storage surface and optimal interactions. Adsorbing electron-rich and easily polarizable molecules into microporous electrodes is expected to boost Faradaic pseudo-activity. If such electrode-electrolyte interactions can be made as a potential-driven reversible process, the resulting capacitors would be adaptable and device-friendly. A composite covalent organic framework (COF)-carbon electrode with redox-active KI is combined in an H2SO4 electrolyte for the first time. This composite electrode benefits from the redox-functionality of COF and electronic conductivity of carbon, leading to superior capacitative activity. Operando spectro-electrochemical measurements reveal the existence of multiple polyiodide species, although the I-3(-) is the predominantly electroactive species adsorbing on the microporous triazine-phenol COF electrode. A systematic fabrication of the flexible solid-state devices using the COF-redox-electrolyte reveals a high areal capacitance of 270 +/- 11 mF cm(-2) and gravimetric capacitance of 57 +/- 8 F g(-1). The inclusion of KI in H2SO4 (electrolyte) yields an approximately eight-fold enhancement in solid-state gravimetric specific capacitance. The imine-COF retains 89\% of its capacity even after 10 000 cycles.

}, keywords = {covalent organic frameworks, polyiodide, redox electrolytes, solid\&\#8208, state capacitors, Supercapacitors}, issn = {1614-6832}, doi = {10.1002/aenm.202003626, Early Access Date = FEB 2021}, author = {Kushwaha, Rinku and Haldar, Sattwick and Shekhar, Pragalbh and Krishnan, Akshara and Saha, Jayeeta and Hui, Pramiti and Vinod, Chathakudath Prabhakaran and Subramaniam, Chandramouli and Vaidhyanathan, Ramanathan} } @article {48183, title = {Synergistic electronic effects in AuCo nanoparticles stabilized in a triazine-based covalent organic framework: a catalyst for methyl orange and methylene blue reduction}, journal = {ACS Applied Nano Materials}, volume = {5}, year = {2022}, month = {APR }, pages = {4744-4753}, type = {Article}, abstract = {

Developing stable active catalysts for reducing water-soluble pollutants is a desirable target. In this pursuit, we have functionalized covalent organic frameworks (COFs) with gold (Au) and cobalt (Co) nanoparticles via a one-step aqueous synthesis process, and their catalytic activity in reducing methyl orange and methylene blue is examined. Operando absorbance measurements of methyl orange (anionic dye) reduction revealed AuCoCOF (1.3 Au/1.0 Co) to have superior kinetics over many other catalysts, which typically require additional external stimuli (e.g., photons) and higher catalyst loadings. After confirming the homogeneous dispersion of the nanoparticles on the COF support using three-dimensional (3D) tomography and material stability through powder X-ray diffraction (PXRD), infrared (IR), and thermal studies, we investigated their redox activity. Cyclic voltammetry (CV) confirmed the involvement of both metals in the redox process, while spectroelectrochemical measurements show that their activity and kinetics remain unaltered by an applied potential. Solid-state UV measurements reveal that the neat COF is a semiconductor with a large band gap (2.8 eV), which is substantially lowered when loaded with cobalt nanoparticles (2.2 eV for CoCOF). The electronic synergy between Au and Co nanoparticles further reduces the band gap of AuCoCOF (1.9 eV). Thus, there is a definite advantage in doping non-noble metal nanoparticles into a noble metal lattice and nanoconfining them into a porous COF support. Our study highlights the significance of bimetallic COF-supported nanocatalysts, wherein one can engage each component toward targeted applications that demand redox activity with favorable kinetics.

}, keywords = {AuCoCOF, band gaps, Covalent organic framework, methyl orange reduction, Nanoparticles, UV-vis spectroscopy}, doi = {10.1021/acsanm.1c04212}, author = {Devulapalli, Venkata Swaroopa Datta and Kushwaha, Rinku and Ovalle, Edwin and Singh, Himan Dev and Shekhar, Pragalbh and Chakraborty, Debanjan and Vinod, Chathakudath Prabhakaran and Vaidhyanathan, Ramanathan and Borguet, Eric} } @article {48735, title = {Made to measure squaramide COF cathode for zinc dual-ion battery with enriched storage via redox electrolyte}, journal = {Advanced Energy Materials}, volume = {13}, year = {2023}, month = {SEP}, type = {Article}, abstract = {

Aqueous rechargeable batteries are promising grid-scale energy storage devices because of their affordability, operational safety, and environmental benignity. Among these, Zn-ion batteries (ZIBs) have unfolded new horizons. Designing superior cathodes for ZIBs is crucial. Covalent organic frameworks (COFs) can be made redox active with a high storage surface. Here, for the first time, a chelating COF with redox-active ZnI2 in a ZnSO4(aq) electrolyte is combined. Including iodide harvests an approximately threefold enhancement in capacity from 208 to 690 mAh g(-1) at 1.5 A g(-1), the highest among all the COF-derived ZIBs. Remarkably, a charge-discharge curve at 1.3 V exhibits very limited dropout voltage and super-flat platform, with a remarkable capacity of 600 mAh g(-1) at 5 A g(-1) stable up to 6000 cycles, confirming that the polyiodide generation and storage are sustainable. The COF{\textquoteright}s dual-ion storage (Zn2+ and polyidode) delivers a ZIB with the highest energy density. Spectro-electrochemical measurements coupled with X-ray photoelectron spectroscopy unambiguously unveil the existence of multiple polyiodide species, with I-3(-) and IO3- ions as the prominent species. The latter gets reduced at the COF electrode under an applied potential, leaving I-3(-) as the major species stored on the COF. The prospect of COF-polyiodide((aq)) is a windfall for metal-ion batteries.

}, keywords = {covalent organic frameworks, flexible batteries, polyiodide, redox electrolytes, Zn ion batteries}, issn = {1614-6832}, doi = {10.1002/aenm.202301049}, author = {Kushwaha, Rinku and Jain, Chitvan and Shekhar, Pragalbh and Rase, Deepak and Illathvalappil, Rajith and Mekan, Deep and Camellus, Augastus and Vinod, Chathakudath Prabhakaran and Vaidhyanathan, Ramanathan} }