Sabuj Kanti Das

A New Triazine-Based Covalent Organic Framework for High-Performance Capacitive Energy Storage

The new covalent organic framework material TDFP-1 was prepared through a solvothermal Schiff base condensation reaction of the monomers 1,3,5-tris-(4-aminophenyl)triazine and 2,6-diformyl-4-methylphenol. Owing to its high specific surface area of 651 m2  g-1 , extended π conjugation, and inherent microporosity, TDFP-1 exhibited an excellent energy-storage capacity with a maximum specific capacitance of 354 F g-1 at a scan rate of 2 mV s-1 and good cyclic stability with 95 % retention of its initial specific capacitance after 1000 cycles at 10 A g-1 . The π-conjugated polymeric framework as well as ionic conductivity owing to the possibility of ion conduction inside the micropores of approximately 1.5 nm make polymeric TDFP-1 a favorable candidate as a supercapacitor electrode material. The electrochemical properties of this electrode material were measured through cyclic voltammetry, galvanic charge-discharge, and electrochemical impedance spectroscopy, and the results indicate its potential for application in energy-storage devices.

Electrochemical Stimuli-Driven Facile Metal-Free Hydrogen Evolution from Pyrene-Porphyrin-Based Crystalline Covalent Organic Framework

A [2 + 2] Schiff base type condensation between 5,10,15,20-tetrakis(4-aminophenyl)porphyrin (TAP) and 1,3,6,8-tetrakis (4-formylphenyl) pyrene (TFFPy) under solvothermal condition yields a crystalline, quasi-two-dimensional covalent organic framework (SB-PORPy-COF). The porphyrin and pyrene units are alternatively occupied in the vertex of 3D triclinic crystal having permanent microporosity with moderately high surface area (∼869 m2 g-1) and promising chemical stability. The AA stacking of the monolayers give a pyrene bridged conducting channel. SB-PORPy-COF has been exploited for metal free hydrogen production to understand the electrochemical behavior using the imine based docking site in acidic media. SB-PORPy-COF has shown the onset potential of 50 mV and the Tafel slope of 116 mV dec-1. We expect that the addendum of the imine based COF would not only enrich the structural variety but also help to understand the electrochemical behavior of these class of materials.

Functionalized graphene oxide as an efficient adsorbent for CO2 capture and support for heterogeneous catalysis

We have designed new imine-functionalized graphene oxide (IFGO) through post synthetic modifications involving co-condensation of 3-aminopropyltriethoxysilane with graphene oxide basal plane containing hydroxyl and epoxy functional groups, followed by Schiff base condensation reaction with 2,6-diformyl-4-methylphenol and impregnation of copper(II) to it through covalent attachment (Cu-IFGO). Powder X-ray diffraction, N2 sorption analysis, FT-IR, HR-TEM, FE-SEM and TGA/DTA analysis are employed to characterize the materials. The IFGO material exhibits good CO2 storage capacity of 8.10 mmol g−1 (35.64 wt%) and 2.10 mmol g−1 (9.24 wt%) at 273 K and 298 K temperature, respectively, up to 3 bar pressure, suggesting its potential application in environmental clean-up. Also, Cu-IFGO showed high catalytic activity in microwave-assisted one-pot three-component C–S coupling reactions for a diverse range of aryl halides with thiourea and benzyl bromide in aqueous medium to obtain aryl thioether products (maximum yield 86%), which are derivatives of natural products. Moreover, having imine and hydroxyl groups in functionalized graphene oxide, the grafted Cu(II) chelated at the graphene oxide surface so strongly that it could not be leached out from the material during the course of the coupling reaction. Thus, it displayed very small decrease in product yield up to the sixth reaction cycle suggesting a sustainable future of this Cu(II)-grafted catalyst.

N-rich Porous Organic Polymer as Heterogeneous Organocatalyst for the One-Pot Synthesis of Polyhydroquinoline Derivatives through the Hantzsch Condensation Reaction

Incorporation of nitrogen functionality onto the high surface area porous polymeric network are very demanding in designing suitable heterogeneous organocatalyst having surface basicity. Here we report the synthesis of a new N‐rich triazine based microporous organic polymer (TrzMOP) through a simple and efficient condensation pathway involving the reaction between 1,4‐bis(4,6‐diamino‐s‐triazin‐2‐yl)‐benzene (SL‐1) and 2,5‐thiophene dicarboxaldehyde. The material has been characterized by using powder XRD, FTIR spectroscopy, solid state magic‐angle spinning 13C NMR, CHN analysis, FESEM, HRTEM, CO2‐TPD and N2 adsorption/desorption techniques. This nitrogen‐rich new porous organic polymer showed very high catalytic efficiency for one‐pot proficient synthesis of polyhydroquinoline derivatives via microwave assisted condensation reaction. As little as 8 mg of catalyst was found to be effective under the optimum reaction conditions. In addition, TrzMOP catalyzed synthesis of biologically active polyhydroquinoline derivatives are very cost effective, scalable, less time consuming, and environmentally benign compared to those of currently used as heterogeneous catalysts.

Role of Surface Phenolic-OH Groups in N-Rich Porous Organic Polymers for Enhancing the CO2 Uptake and CO2/N2 Selectivity: Experimental and Computational Studies

Design and successful synthesis of phenolic-OH and amine-functionalized porous organic polymers as adsorbent for postcombustion CO2 uptake from flue gas mixtures along with high CO2/N2 selectivity is a very demanding research area in the context of developing a suitable adsorbent to mitigate greenhouse gases. Herein, we report three triazine-based porous organic polymers TrzPOP-1, -2, and -3 through the polycondensation of two triazine rings containing tetraamine and three dialdehydes. These porous organic polymers possess high Brunauer-Emmett-Teller (BET) surface areas of 995, 868, and 772 m2 g-1, respectively. Out of the three materials, TrzPOP-2 and TrzPOP-3 contain additional phenolic-OH groups along with triazine moiety and secondary amine linkages. At 273 K, TrzPOP-1, -2, and -3 displayed CO2 uptake capacities of 6.19, 7.51, and 8.54 mmol g-1, respectively, up to 1 bar pressure, which are considerably high among all porous polymers reported till date. Despite the lower BET surface area, TrzPOP-2 and TrzPOP-3 containing phenolic-OH groups showed higher CO2 uptakes. To understand the CO2 adsorption mechanism, we have further performed the quantum chemical studies to analyze noncovalent interactions between CO2 molecules and different polar functionalities present in these porous polymers. TrzPOP-1, -2, and -3 have the capability of selective CO2 uptake over that of N2 at 273 K with the selectivity of 61:1, 117:1, and 142:1 by using the initial slope comparing method, along with 108.4, 140.6, and 167.4 by using ideal adsorbed solution theory (IAST) method, respectively. On the other hand, at 298 K, the calculated CO2/N2 selectivities in the initial slope comparing method for TrzPOP-1, -2, and -3 are 27:1, 72:1, and 96:1, whereas those using IAST method are 42.1, 75.7, and 94.5, respectively. Cost effective and scalable synthesis of these porous polymeric materials reported herein for selective CO2 capture has a very promising future for environmental clean-up.