SANDEEP KUMAR
@iitrpr.ac.in
Research Scholar and Department of Chemistry, IIT Ropar
IIT Ropar
RESEARCH INTERESTS
Computational Material Chemistry
Scopus Publications
Scopus Publications
Deepti Sharma, Selvakumar Balasubramaniam, Sandeep Kumar, Eluvathingal D. Jemmis, and Ajay Venugopal
Royal Society of Chemistry (RSC)
Investigations on the boundaries between the neutral and cationic models of (Mesityl)2EX (E = Sb, Bi and X = Cl−, OTf−) have facilitated reversing the Lewis acidity from bismuth to antimony.
Ramkumar Kannan, Selvakumar Balasubramaniam, Sandeep Kumar, Raju Chambenahalli, Eluvathingal D. Jemmis, and Ajay Venugopal
Wiley
Bismuth compounds are desirable green alternatives to transition metal complexes in catalysis. In this work, we generate a dicationic organobismuth compound [(Me 2 NC 6 H 4 )Bi(L) 3 ][B(C 6 H 3 Cl 2 ) 4 ] 2 (L=aldehyde/ketone) in dichloromethane which efficiently catalyzes hydrosilylation of aldehydes and ketones resulting in silyl ethers as the only products in high yields. Computational analysis on the two-coordinate [(Me 2 NC 6 H 4 )Bi] 2+ possessing three electrophilic sites is experimentally evidenced by the isolation of [{Me 2 NC 6 H 4 }Bi{OP(NMe 2 ) 3 } 3 ][B(C 6 H 3 Cl 2 ) 4 ] 2 . Our investigations support a carbonyl activation mechanism at the bismuth center followed by Si-H addition.
Selvakumar Balasubramaniam, Sandeep Kumar, Alex P. Andrews, Eluvathingal D. Jemmis, and Ajay Venugopal
Wiley
Feixiong Liu, Sandeep Kumar, Shuangshuang Li, Hengzhi You, Peng Ren, and Limin Zhao
Elsevier BV
Abstract A highly water stable zinc metal–organic framework (ZnMOF), {[Zn(HL)2]}n, was synthesized using a triazole–carboxylate-based mixed ligand (L = 5-(4H-1,2,4-triazol-4-yl)isophthalic acid). A 2D MOF was formed by hydrothermal synthesis, and extended to a 3D supramolecular network through strong hydrogen bonding. This MOF was fully characterized by Fourier-transformation infrared spectroscopy, thermogravimetric analysis, single-crystal X-ray diffraction (XRD), powder XRD and elemental analysis. Owing to the d10 configuration of this ZnMOF, its luminescent properties were suitable for the sensing of the CN− ions over other anions, as inferred from the florescence result. However, regarding the catalytic mechanism, this ZnMOF showed a strong ability to react with CN−, which might be due to the hydrogen bonding between the COOH groups without coordination. This interaction behavior with CN− ions makes the ZnMOF a promising heterogeneous catalyst for Knoevenagel condensations using malononitrile and aldehyde derivatives as reactants under mild conditions. All reactions were conducted in water as a green solvent.
Sandeep Kumar and T.J. Dhilip Kumar
Elsevier BV
Abstract Hydrogen holds the promise for alternative clean energy carrier due to its renewable and pollution free nature. A metal-organic framework (MOF) is designed with graphyne linker. Each graphyne linker is decorated with two Ca atoms across the linker with average metal binding energy 3.0 eV. The structural, electronic and hydrogen storage properties of Ca decorated MOF have been explored by using first principle calculations. On full saturation with hydrogen, each Ca atom of MOF-Ca8 adsorbs a maximum of six H2 molecules and results in MOF-Ca8-48H2 structure. Further twelve more hydrogen molecules could be accommodated in the pore space of MOF resulting in the MOF-Ca8-60H2 structure having 7.9 hydrogen wt%. According to the simulations, the H2 molecules can be adsorbed on Ca by Kubas mechanism with elongation in H − H bond distance. The calculated hydrogen interaction energy is found in the range between 0.25 and 0.30 eV while desorption energy varies between 0.15 and 0.32 eV. The charge transfer during hydrogen adsorption is investigated by Hirshfeld charge analysis and electrostatic potential map. The molecular dynamics simulations revealed a high degree of reversibility in hydrogen adsorption of the system at ambient conditions. The usable capacity of H2 is explored by calculating occupation number at adsorption and desorption conditions. The energetics and storage capacity meets the US DOE target which makes the MOF-Ca8 as a potential hydrogen storage material.
Alexander Asiedu, Ryan Davis, and Sandeep Kumar
Elsevier BV
Abstract Oil-laden biofuel intermediate (BI) from flash-hydrolyzed microalgae was characterized, pyrolyzed, and subjected to catalytic transfer hydrogenation (CTH) to produce both gaseous and liquid hydrocarbon fuels. The BI was characterized by TGA and FTIR that revealed significant triglyceride, evidenced by C O bond with insignificant level of carbohydrates and proteins. Thermogravimetric analysis (TGA) indicated that the BI could be thermally decomposed at 400 °C. Pyrolysis of the BI engendered mainly gaseous hydrocarbon (alkenes) with high heating value (HHV) of 48.5 kJ/mol at 850 °C. Energy of activation for the pyrolytic process was estimated to be 115–300 kJ/mol. Optimization of oil extraction from the BI was performed via design of experiment. The oil was subjected to CTH over NiOx-CoOx-MoOx-zeolite using 2-propanol as hydrogen donor in a 30-ml batch reactor at a temperature range of 390–420 °C and autogenic pressure of 24–27 bar, leading to fatty acid conversion of 99–100%. The main liquid products obtained from the CTH were iso-alkanes (41%), cyclo-alkanes (35%), aromatics (5%), n-alkanes (14%), and alkenes (5%). Kinetics of the CTH showed first order with activation energy of 176 kJ/mol. The catalyst was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Brunaeur-Emmett-Teller (BET) adsorption and desorption, scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and TGA. The catalyst revealed cubic structure, which was maintained after 5 h of CTH reaction. Present in both the fresh and the used catalysts were oxides of alkali and transition metals. The active sites of the catalyst were dominated by Co3+, Ni2+, and Mo6+.
Rohit Y. Sathe, Sandeep Kumar, and T. J. Dhilip Kumar
AIP Publishing
We present the detailed comparative study of dihydrogen adsorption in Li, Mg, Ca, and Sc decorated γ-graphyne (G γ) performed with density functional theory calculations. Hydrogen molecules are sequentially loaded onto metal decorated G γ. Maximum hydrogen weight percentage for Li, Mg, Ca, and Sc decorated G γ is found to be 8.69, 7.73, 8.10, and 6.83, respectively, with maximum 8 H 2 on Li, Mg, and Sc while 10 on Ca decorated G γ. All hydrogen molecules are physisorbed over all the complexes except that the first one on each Sc of G γ-2Sc is chemisorbed. Orbital hybridization involved in Dewar coordination of metal decoration and the Kubas mechanism of hydrogen adsorption has been explained with the partial density of states. Lower values of adsorption and desorption energies in these complexes indicate the reversibility of adsorption. These complexes obey high hardness and low electrophilicity principles and contain no imaginary frequencies which specify their stability. In Born-Oppenheimer molecular dynamics, reversibility of adsorption is proven at various temperatures. Based on the comparative studies of hydrogen weight percentage, energetics, stability, and reversibility, G γ-2Ca is proven to be a better hydrogen storage candidate. This comprehensive study confirms the potential of metal decorated γ-graphyne as a suitable hydrogen storage material.We present the detailed comparative study of dihydrogen adsorption in Li, Mg, Ca, and Sc decorated γ-graphyne (G γ) performed with density functional theory calculations. Hydrogen molecules are sequentially loaded onto metal decorated G γ. Maximum hydrogen weight percentage for Li, Mg, Ca, and Sc decorated G γ is found to be 8.69, 7.73, 8.10, and 6.83, respectively, with maximum 8 H 2 on Li, Mg, and Sc while 10 on Ca decorated G γ. All hydrogen molecules are physisorbed over all the complexes except that the first one on each Sc of G γ-2Sc is chemisorbed. Orbital hybridization involved in Dewar coordination of metal decoration and the Kubas mechanism of hydrogen adsorption has been explained with the partial density of states. Lower values of adsorption and desorption energies in these complexes indicate the reversibility of adsorption. These complexes obey high hardness and low electrophilicity principles and contain no imaginary frequencies which specify their stability. In Born-Oppe...
Selvakumar Balasubramaniam, Sandeep Kumar, Alex P. Andrews, Babu Varghese, Eluvathingal D. Jemmis, and Ajay Venugopal
Wiley
Invited for the cover of this issue is Ajay Venugopal from the Indian Institute of Science Education and Research Thiruvananthapuram. The cover image shows dication Tp(Me2)Bi](2+) catalyzing olefin hydrosilylation under mild conditions.
Sandeep Kumar, Surinder Pal Kaur, and T. J. Dhilip Kumar
American Chemical Society (ACS)
The need for sustainable energy fuel is much higher than before. The use of hydrogen as a fuel is impeded due to its low storage capacity in the storage medium. In this work, a newly designed metal...
Sandeep Kumar, Rohit Y. Sathe, and T.J. Dhilip Kumar
Elsevier BV
Abstract Using the idea of metal functionalized material for H2 storage, 4-tert-butylcalix[4]arene (CA) functionalized with Sc and Ti atoms are explored. The first principles density functional theory (DFT) with M06 functional and 6-311G(d,p) basis set is used to explore the hydrogen storage properties of metal functionalized CA. Sc and Ti strongly binds with CA by Dewar coordination with high binding energy. It is found that maximum four hydrogen molecules are adsorbed on each metal site in Sc and Ti functionalized CA. Hydrogen molecules are adsorbed on metals by Kubas and Niu-Rao-Jena mechanism. In Sc functionalized CA system all 4 hydrogen molecules on each Sc bind in molecular fashion while on each Ti in Ti functionalized CA, the first hydrogen molecule binds in dissociative fashion and remaining three hydrogen molecules bind in a molecular form. The stability of Sc and Ti functionalized CA is studied by computing conceptual DFT parameters, which obeys maximum hardness and minimum electrophilicity principle. Hirshfeld charge analysis and electrostatic potential map explore the charge transfer mechanism during the hydrogen adsorption. Born-Oppenheimer molecular dynamics simulations are performed at temperature range 200–473 K to study the stability of the system and the reversibility of adsorbed hydrogen from the system. The calculated H wt% is found to be 10.3 and 10.1, respectively for Sc and Ti functionalized CA systems on complete H2 saturation. This study explores that Sc and Ti functionalized CA systems are efficient reversible hydrogen storage material.
Rohit Y. Sathe, Sandeep Kumar, and Thogluva Janardhanan Dhilip Kumar
Elsevier BV
Abstract Use of metal functionalized molecules for reversible hydrogen storage is well established due to their high gravimetric hydrogen storage capacity. We study BN-analogue of [2,2]paracyclophane (BNP22) containing two borazine rings and functionalized with Sc and Ti atoms to interpret its hydrogen binding capacity. First principles calculations based on density functional theory suggest that BNP22-2Sc and BNP22 2Ti systems can have a gravimetric density as high as 8.9 and 9.9 % , respectively. The BNP22-2Sc system can be operated under ambient thermodynamic conditions within the allowable pressure range of 3–30 atm and van ‘t Hoff desorption temperature range of 219–438 K as confirmed from molecular dynamics and occupation number studies. Both the systems establish Bronsted-Evans-Polanyi relation with BNP22-2Sc having significantly less activation energy of 0.38 eV. We discuss the energetic stability of these systems with respect to vibrational frequency, absolute hardness, and transition states. Consistent with 2020 targets set by the DOE, BNP22-2Sc proves to be budding hydrogen storage material.
Sandeep Kumar, Rohit Y. Sathe, and T.J. Dhilip Kumar
Elsevier BV
Abstract The use of hydrogen as a sustainable clean energy source has several benefits, such as reduction in dependency on petroleum fuel and emission of green house gases, and enhanced energy security. The H2 storage properties of Sc grafted calix[4]arene (CX) and octamethylcalix[4]arene (MCX) are investigated by using density functional theory with M06/6-311G(d,p) level of theory. It is observed that Sc strongly binds with benzene rings of CX and MCX through Dewar coordination with average Sc binding energy of 1.09 and 1.25 eV, respectively for CXSc4 and MCXSc4. Each Sc atom adsorbs 4 H2 molecules on both the Sc grafted systems and H2 molecules are bound by Kubas interaction with H2 interaction energy in the range of 0.2–0.5 eV. The calculated conceptual reactivity index shows the stability of the systems increases with number of hydrogen molecules. Hirshfeld charge analysis shows the charge transfer mechanism during H2 adsorption. Born-Oppenheimer molecular dynamics simulations of CXSc4-16H2 and MCXSc4-16H2 systems, show that these systems are stable up to 273 K and all the adsorbed H2 releases at 373 K. The hydrogen storage capacity of Sc grafted CX system is found to be 8.9 wt % and for MCX system is 9.7 wt %. The energy and storage capacity meets the US Department of Energy target, which makes them a propitious hydrogen storage material.
Bharat Ugale, Sandeep Kumar, T. J. Dhilip Kumar, and C. M. Nagaraja
American Chemical Society (ACS)
Highly porous, polyhedral metal-organic frameworks (MOFs) of Co(II)/Ni(II), {[M6(TATAB)4(DABCO)3(H2O)3]·12DMF·9H2O} n (where M = Co(II) (1)/Ni(II) (2), H3TATAB = 4,4',4″- s-triazine-1,3,5-triyl-tri- p-aminobenzoic acid, and DABCO = 1,4-diazabicyclo[2.2.2]octane) have been synthesized solvothermally. Both MOFs 1 and 2 show a 2-fold interpenetrated 3D framework structure composed of dual-walled cages of dimension ∼ 30 Å functionalized with a high density of Lewis acidic Co(II)/Ni(II) metal sites and basic -NH- groups. Interestingly, MOF 1 shows selective adsorption of CO2 with high heat of adsorption ( Qst) value of 39.7 kJ/mol that is further supported by theoretical studies with computed binding energy (BE) of 41.17 kJ/mol. The presence of the high density of both Lewis acidic and basic sites make MOFs 1/2 ideal candidate materials to carry out co-catalyst-free cycloaddition of CO2 to epoxides. Consequently, MOFs 1/2 act as excellent recyclable catalysts for cycloaddition of CO2 to epoxides for high-yield synthesis of cyclic carbonates under co-catalyst-free mild conditions of 1 bar of CO2. Further, MOF 1 was recycled for five successive cycles without substantial loss in catalytic activity. Herein, rational design of rare examples of 3D polyhedral MOFs composed of Lewis acidic and basic sites exhibiting efficient co-catalyst-free conversion of CO2 has been demonstrated.
Nayuesh Sharma, Sandeep Singh Dhankhar, Sandeep Kumar, T. J. Dhilip Kumar, and C. Mallaiah Nagaraja
Wiley
A 3D MnII -porphyrin metal-organic framework (MOF), [{Mn2 (TCPP)⋅2H2 O}⋅DMF]n (MOF1) (TCPP=5,10,15,20-tetrakis(4-benzoate)porphyrin), was constructed; it exhibits an interesting 3D framework structure with two types of 1D channels of dimensions of 3.94×8.37 Å2 and 4.66×4.93 Å2 running along the crystallographic a axis. Owing to the presence of a nonmetallated porphyrin cavity, MOF1 exhibits selective storage of CO2 with an isosteric heat of adsorption value of 32.1 kJ mol-1 , which is further supported by theoretical calculations with the calculated binding energy (BE) of 29.78 kJ mol-1 . Interestingly, the nonmetallated nature of the porphyrin ligand was exploited for implantation of coordinatively unsaturated FeIII ions to generate a FeIII @MOF1 framework, which acts as an efficient recyclable catalyst for the oxidation of styrenes to the corresponding epoxides in the presence of PhIO as an oxidant at room temperature. Moreover, the one-pot synthesis of styrene carbonates from styrenes and CO2 was also achieved using FeIII @MOF1 as a catalyst. The rational design of a porous MnII -porphyrin MOF for the selective capture of CO2 and the one-pot synthesis of styrene carbonates at mild conditions is reported.
Sandeep Kumar, Madhu Samolia, and Thogluva Janardhanan Dhilip Kumar
American Chemical Society (ACS)
Hydrogen is a versatile, clean, and efficient energy carrier considered as an ideal substitute for a future energy source in the automobile industry. A metal–inorganic framework with borazocine (BN) linker resulting in a metal–BN framework (MBF) has been studied for hydrogen storage. Borazocine (B4N4H8) is decorated with metals, M (Sc, Li), and studied the stability and hydrogen storage capacity. Density functional theory with generalized gradient approximation and Perdew–Burke–Ernzerhof functional with double numeric polarized basis set augmented with p-function are used to explore the structural stability, and hydrogen sorption kinetics of metal decorated MBF. It is observed that each Sc and Li physisorbed 4 and 3 H2 molecules, respectively. The BN ring binds with metals (Sc and Li) by Dewar coordination while the metal atoms adsorb H2 molecules by the Kubas–Niu–Rao–Jena mechanism. Molecular dynamics simulations show that the Sc decorated MBF system is stable and the adsorbed hydrogen is reversible at a...
Rohit Y. Sathe, Sandeep Kumar, and Thogluva Janardhanan Dhilip Kumar
Elsevier BV
Abstract Storing hydrogen for commercial purpose with high gravimetric density is a major task. Li and Sc are functionalized over delocalized π electrons of [4,4]paracyclophane to explore reversible hydrogen storing capacity. Electronic structure calculations are performed with Minnesota 06 hybrid functional and 6-311G(d,p) basis set. [4,4]paracyclophane binds strongly to Sc showing Dewar coordination. Sc functionalized [4,4]paracyclophane complex has a capacity of holding 10 H2 molecules while Li functionalized complex holds 8 H2 molecules with hydrogen weight percentage of 11.8% and 13.7% respectively. Conceptual DFT parameters namely hardness and electrophilicity confirm the high stability of the complexes. Atom Density Matrix Propagation simulations at various temperatures and their desorption pattern indicate reversibility of adsorbed hydrogens. The study confirms the potential of Sc functionalized [4,4]paracyclophanes as a hydrogen storage material.
Sandeep Singh Dhankhar, Nayuesh Sharma, Sandeep Kumar, T. J. Dhilip Kumar, and C. M. Nagaraja
Wiley
A bifunctional, microporous ZnII metal-organic framework, [Zn2 (NH2 BDC)2 (dpNDI)]n (MOF1) (where, NH2 BDC=2-aminoterephthalic acid, dpNDI=N,N'-di(4-pyridyl)-1,4,5,8-naphthalenediimide) has been synthesized solvothermally. MOF1 shows an interesting two-fold interpenetrated, 3D pillar-layered framework structure composed of two types of 1D channels with dimensions of approximately 2.99×3.58 Å and 4.58×5.38 Å decorated with pendent -NH2 groups. Owing to the presence of a basic functionalized pore surface, MOF1 exhibits selective adsorption of CO2 with high value of heat of adsorption (Qst =46.5 kJ mol-1 ) which is further supported by theoretically calculated binding energy of 48.4 kJ mol-1 . Interestingly, the value of Qst observed for MOF1 is about 10 kJ mol-1 higher than that of analogues MOF with the benzene-1,4-dicarboxylic acid (BDC) ligand, which establishes the critical role of the -NH2 group for CO2 capture. Moreover, MOF1 exhibits highly selective and sensitive sensing of the nitroaromatic compound (NAC), 2,4,6-trinitrophenol (TNP) over other competing NACs through a luminescence quenching mechanism. The observed selectivity for TNP over other nitrophenols has been correlated to stronger hydrogen bonding interaction of TNP with the basic -NH2 group of MOF1, which is revealed from DFT calculations. To the best of our knowledge, MOF1 is the first example of an interpenetrated ZnII -MOF exhibiting selective adsorption of CO2 as well as efficient aqueous-phase sensing of TNP; investigated through combined experimental and theoretical studies.
Sandeep Kumar and Thogluva Janardhanan Dhilip Kumar
American Chemical Society (ACS)
Porous metal-graphyne framework (MGF) made up of graphyne linker decorated with lithium has been investigated for hydrogen storage. Applying density functional theory spin-polarized generalized gradient approximation with the Perdew-Burke-Ernzerhof functional containing Grimme's diffusion parameter with double numeric polarization basis set, the structural stability, and physicochemical properties have been analyzed. Each linker binds two Li atoms over the surface of the graphyne linker forming MGF-Li8 by Dewar coordination. On saturation with hydrogen, each Li atom physisorbs three H2 molecules resulting in MGF-Li8-H24. H2 and Li interact by charge polarization mechanism leading to elongation in average H-H bond length indicating physisorption. Sorption energy decreases gradually from ≈0.4 to 0.20 eV on H2 loading. Molecular dynamics simulations and computed sorption energy range indicate the high reversibility of H2 in the MGF-Li8 framework with the hydrogen storage capacity of 6.4 wt %. The calculated thermodynamic practical hydrogen storage at room temperature makes the Li-decorated MGF system a promising hydrogen storage material.
Sandeep Kumar and T. J. Dhilip Kumar
American Chemical Society (ACS)
Hydrogen is the most promising candidate for a sustainable energy source in the transport sector. However, the storage of hydrogen is a major problem. Calix[4]arene (CX) is functionalized with Ti and Li metals on the delocalized π electrons of benzene rings, and the metal-functionalized system is studied for hydrogen storage efficiency by applying density functional theory using the M06 hybrid functional and 6-311G(d,p) basis set. The calculated binding energy indicates Ti coordinates with CX strongly while Li coordinates weakly and the binding of CX and metal is through Dewar mechanism. On saturation with hydrogen, each Ti atom traps four H2 molecules while each Li atom traps three H2 molecules on CX. Hydrogen molecules are adsorbed on the metal atoms by Kubas–Niu–Rao–Jena interaction. The global reactivity index obtained for the system obeys the maximum hardness and minimum electrophilicity principle. Molecular dynamics simulations are performed using spin-polarized generalized gradient approximation wi...
Sandeep Kumar, Rohit Y. Sathe, and T. J. Dhilip Kumar
Royal Society of Chemistry (RSC)
Ti decorated calix[4]pyrrole and octamethylcalix[4]pyrrole is explored as a potential H2storage material.
Sandeep Kumar, Arvind kumar, K. Durga Bhaskar Yamajala, Pinki Gaur, Deepak Kumar, and SHAIBAL BANERJEE
Lukasiewicz Research Network - Institute of Industrial Organic Chemistry
A group of polycyclic and aliphatic azido-esters (as energetic plasticizers) have been synthesized by simple synthetic routes and their molecular structures were confirmed by spectroscopic techniques. In addition, their thermal and rheological properties have been determined utilizing DSC, TGA, viscosity, and contact angle. Computational studies of these plasticizers have been performed by means of DFT (B3LYP/6-31G*) to estimate possible stable structures, energies, heat of formation, bond dissociation energies, IR and NMR spectra etc. Their compatibility with glycidyl azide polymer (GAP) binder was studied to explore their applicability in propellants. All of these molecules are novel and have been synthesized with the possibility of scale up.