@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 {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} } @article {48953, title = {Tailoring COFs: transforming nonconducting 2D layered COF into a conducting quasi-3D architecture via interlayer knitting with polypyrrole}, journal = {Journal of the American Chemical Society}, volume = {146}, year = {2023}, month = {DEC}, pages = {487-499}, type = {Journal Article}, abstract = {

Improving the electronic conductivity and the structural robustness of covalent organic frameworks (COFs) is paramount. Here, we covalently cross-link a 2D COF with polypyrrole (Ppy) chains to form a quasi-3D COF. The 3D COF shows well-defined reflections in the SAED patterns distinctly indexed to its modeled crystal structure. This knitting of 2D COF layers with conjugated polypyrrole units improves electronic conductivity from 10(-9) to 10(-2 )S m(-1). This conductivity boost is affirmed by the presence of density of states near the Fermi level in the 3D COF, and this elevates the COF{\textquoteright}s valence band maximum by 0.52 eV with respect to the parent 2D pyrrole-functionalized COF, which agrees well with the opto-electro band gaps. The extent of HOMO elevation suggests the predominant existence of a polaron state (radical cation), giving rise to a strong EPR signal, most likely sourced from the cross-linking polypyrrole chains. A supercapacitor devised with COF20-Ppy records a high areal capacitance of 377.6 mF cm(-2), higher than that of the COF loaded with noncovalently linked polypyrrole chains. Thus, the polypyrrole acts as a {\textquoteleft}{\textquoteleft}conjugation bridge{\textquoteright}{\textquoteright} across the layers, lowering the band gap and providing polarons and additional conduction pathways. This marks a far-reaching approach to converting many 2D COFs into highly ordered and conducting 3D ones.

}, keywords = {covalent organic frameworks, Electrical conductivity}, issn = {0002-7863}, doi = {10.1021/jacs.3c09937}, author = {Jain, Chitvan and Kushwaha, Rinku and Rase, Deepak and Shekhar, Pragalbh and Shelke, Ankita and Sonwani, Disha and Ajithkumar, Thalasseril G. and Vinod, Chathakudath Prabhakaran and Vaidhyanathan, Ramanathan} }