Research Interest
The area of interest covers mainly inorganic and materials chemistry. It includes coordination chemistry, host-guest chemistry, electrochemistry of inorganic materials, adsorption and conduction, catalysis, etc
I have significant expertise in synthesis, characterizations of Metal-Organic Frameworks (MOFs) and their application in the area of proton conduction, gas adsorption, drug encapsulation and release, chemical sensing and catalytic performance and other electrochemical application. In addition to these, I also have a collective experience in design and synthesis of Covalent Organic Frameworks (COFs), another emerging class of lightweight porous materials. I would like to expand my professional horizons by seeking new challenges in these areas.
Chemical Sensing:
A new Mg(II) based photochromic porous metal–organic framework (MOF) has been synthesized bearing naphthalenediimide (NDI) chromophoric unit. This MOF (Mg–NDI) shows instant and reversible solvatochromic behavior in presence of solvents with different polarity. Mg–NDI also exhibits fast and reversible photochromism via radical formation. Due to the presence of electron deficient NDI moiety, this MOF exhibits selective organic amine (electron rich) sensing in solid state. The organic amine detection has been confirmed by photoluminescence quenching experiment and visual color change.
Metal-Organic Polyhedra (MOP):
Few layer thick metal-organic nanosheets have been synthesized using water-assisted solid state transformation through a combined top-down and bottom-up approach. The metal-organic polyhedra (MOPs) convert into metal-organic frameworks (MOFs) which subsequently self-exfoliate into few layered metal-organic nanosheets. These MOP crystals experience a hydrophobicity gradient with the inner surface during contact with water because of the existence of hydrophobic spikes on their outer surface. When the amount of water available for interaction is higher, the resultant layers are not stacked to form bulk materials; instead few layered nanosheets with high uniformity were obtained in high yield. The phenomenon has resulted high yield production of uniformly distributed layered metal-organic nanosheets from three different MOPs, showing its general adaptability.
Covalent-Organic Framework (COF) Nano-Structures:
Covalent organic frameworks (COFs) were synthesized using combined reversible and irreversible organic reactions. Syntheses of these COFs were done by the Schiff base reactions of 1,3,5-triformylphloroglucinol (Tp) with diamine (in 1:1 mesitylene/dioxane. The expected enol−imine (OH) form underwent irreversible proton tautomerism, and only the keto−enamine form was observed. Because of the irreversible nature of the total reaction and the absence of an imine bond in the system, TpPa-1 and TpPa-2 showed strong resistance toward acid (9 N HCl) and boiling water. Moreover, TpPa-2 showed exceptional stability in base (9 N NaOH) as well. Hollow and tubular TpPa-COF structures have been synthesized by template-assisted replication of nanometer sized ZnO-nanorods. The hollow structures composed of microporous TpPa shells have high periodicity, moderate porosity, chemical stability and capsule shaped morphology as revealed by X-ray diffraction, porosity measurements, and SEM and TEM analyses.
Proton Conduction in MOF Channels:
we have studied the crystal structure and the proton conductivity of five Ca-MOFs at variable temperature and relative humidity. Ca–BTC–H2O shows a high conductivity of 1.2 × 10-4 S cm-1 and exhibits low activation energy of 0.18 eV and the water content per Ca unit is 1.00. Whereas Ca–BTC– DMF and Ca–BTC–DMA have water content per Ca unit of 0.66 and 0.50, which show 4.8 × 10-5 S cm-1 and 1.46 × 10-5 S cm-1 proton conductivity and 0.32 and 0.40 eV activation energy, respectively. Whereas Ca–BTC does not show proton conductivity because the water content per Ca unit is 0.00. Hence we believe that the extent of water content per metal unit plays a key role in high proton conduction under humidified conditions. We hope that these kinds of materials will provide a roadmap towards the synthesis of controllable proton-conducting materials by varying the water content per metal center.
Ultra-stable MOFs as Energy Storage Materials:
Here we report for the first time, the synthesis of a pre-designed Zr-based-MOF having a redox active organic linker and evaluate it as a supercapacitor electrode. Specifically, we have deliberately incorporated a naphthalenediimide (NDI) core as redox center, which exhibits a two-step redox process, in our organic linker. The combination of the high porosity of the designed Zr-NDI-MOF and the incorporated NDI redox centers contribute double-layer and pseudo-capacitance, respectively, leading to enhanced capacitance performance of this new MOF. The post-synthetic modification of the Zr-NDI-MOFs using organic pillars, to make the structure more rigid, has led to enhanced surface area and consequently increased the capacitance of this MOF by almost a factor of two. This result shows that our rational MOF design strategy can serve as a model for development of similar MOFs for capacitive energy storage application.
