Richa Rajak
@iiti.ac.in
PhD Scholar
IIT Indore
RESEARCH INTERESTS
Inorganic Chemistry
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
Richa Rajak, Parasar Kumar, and Srinivas Dharavath
American Chemical Society (ACS)
Richa Rajak, Navaneet Kumar, Vikas D. Ghule, and Srinivas Dharavath
American Chemical Society (ACS)
Due to the inherent conflict between energy and safety, the construction of energetic materials or energetic metal-organic frameworks (E-MOFs) with balanced thermal stability, sensitivity, and high detonation performance is challenging for chemists worldwide. In this regard, in recent times self-assembly of energetic ligands (high nitrogen- and oxygen-containing small molecules) with alkali metals were probed as a promising strategy to build high-energy materials with excellent density, insensitivity, stability, and detonation performance. Herein, based on the nitrogen-rich N,N'-([4,4'-bi(1,2,4-triazole)]-3,3'-dial)dinitramide (H2BDNBT) energetic ligand, two new environmentally benign E-MOFs including potassium [K2BDNBT]n (K-MOF) and sodium [Na2BDNBT]n (Na-MOF) have been introduced and characterized by NMR, IR, TGA-DSC, ICP-MS, PXRD, elemental analyses, and SCXRD. Interestingly, Na-MOF and K-MOF demonstrate solvent-free 3D dense frameworks having crystal densities of 2.16 and 2.14 g cm-3, respectively. Both the E-MOFs show high detonation velocity (VOD) of 8557-9724 m/s, detonation pressure (DP) of 30.41-36.97 GPa, positive heat of formation of 122.52-242.25 kJ mol-1, and insensitivity to mechanical stimuli such as impact and friction (IS = 30-40 J, FS > 360 N). Among them, Na-MOF has a detonation velocity (9724 m/s) superior to that of conventional explosives. Additionally, both the E-MOFs are highly heat-resistant, having higher decomposition (319 °C for K-MOF and 293 °C for Na-MOF) than the traditional explosives RDX (210 °C), HMX (279 °C), and CL-20 (221 °C). This stability is ascribed to the extensive structure and strong covalent interactions between BDNBT2- and K(I)/Na(I) ions. To the best of our knowledge, for the first time, we report dinitramino-based E-MOFs as highly stable secondary explosives, and Na-MOF may serve as a promising next-generation high-energy-density material for the replacement of presently used secondary thermally stable energetic materials such as RDX, HNS, HMX, and CL-20.
Abhishek Kumar Yadav, Richa Rajak, Vikas D. Ghule, and Srinivas Dharavath
Royal Society of Chemistry (RSC)
In energetic materials research, energetic coordination compounds (ECCs) have received much attention due to their high thermal stability and insensitivity to mechanical stimuli.
Richa Rajak, Parasar Kumar, Vikas D. Ghule, and Srinivas Dharavath
American Chemical Society (ACS)
Poly tetrazole-containing thermally stable and insensitive alkali metal-based 3D energetic metal-organic frameworks (EMOFs) are promising high energy density materials to balance the sensitivity, stability, and detonation performance of explosives in defense, space, and civilian applications. Herein, the self-assembly of L3- ligand with alkali metals Na(I) and K(I) was prepared at ambient conditions, introducing two new EMOFs, [Na3(L)3(H2O)6]n (1) and [K3(L)3(H2O)3]n (2). Single crystal analysis reveals that Na-MOF (1) exhibited a 3D wave-like supramolecular structure with significant hydrogen bonding among the layers, while K-MOF (2) also featured a 3D framework. Both EMOFs were thoroughly characterized by NMR, IR, PXRD, and TGA/DSC analyses. Compounds 1 and 2 show excellent thermal decomposition Td = 344 and 337 °C, respectively, compared to the presently used benchmark explosives RDX (210 °C), HMX (279 °C), and HNS (318 °C), which is attributed to structural reinforcement induced by extensive coordination. They also show remarkable detonation performance (VOD = 8500 m s-1, 7320 m s-1, DP = 26.74 GPa, 20 GPa for 1 and 2, respectively) and insensitivity toward impact and friction (IS ≥ 40 J, FS ≥ 360 N for 1; IS ≥ 40 J, FS ≥ 360 N for 2). Their excellent synthetic feasibility and energetic performance suggest that they are the perfect blend for the replacement of present benchmark explosives such as HNS, RDX, and HMX.
Rakesh Deka, Richa Rajak, Viresh Kumar, and Shaikh M. Mobin
American Chemical Society (ACS)
A cadmium-based metal-organic framework (Cd-MOF) is synthesized in a facile manner at ambient temperature by an easy slow diffusion process. The three-dimensional (3D) structure of Cd-MOF is authenticated by single-crystal X-ray diffraction studies and exhibits a cuboid-shaped morphology with an average edge length of ∼1.13 μm. The prepared Cd-MOF was found to be electroactive in nature, which resulted in a specific capacitance of 647 F g-1 at 4 A g-1 by maintaining a retention of ∼78% over 10,000 successive cycles in the absence of any binder. Further, to distinguish the efficiency of Cd-MOF electrodes, different electrolytes (NaOH, KOH, and LiOH) were explored, wherein NaOH revealed a higher capacitive response due to its combined effect of ionic and hydrated ionic radii. To investigate the practical applicability, an asymmetric supercapacitor (ASC) device is fabricated by employing Cd-MOF as the positive electrode and activated carbon (AC) as the negative electrode, enabling it to light a commercial light-emitting diode (LED) bulb (∼1.8 V). The as-fabricated ASC device delivers comparable energy density and power density.
Rakesh Deka, Viresh Kumar, Richa Rajak, and Shaikh M. Mobin
Royal Society of Chemistry (RSC)
A nickel based coordination polymer (Ni-CP) is synthesized by slow diffusion technique which reveals a 2D layer like structure having sql topology, further this Ni-CP was employed for high performance supercapacitor application.
Richa Rajak, Mohit Saraf, Praveen Kumar, Kaushik Natarajan, and Shaikh M. Mobin
American Chemical Society (ACS)
Recently, metal-organic frameworks (MOFs) have been widely employed as a sacrificial template for the construction of nanostructured materials for a range of applications including energy storage. Herein, we report a facile mixed-ligand strategy for the synthesis of a Cu-MOF, [Cu3(Azopy)3(BTTC)3(H2O)3·2H2O]n (where BTTC = 1,2,4,5-benzenetetracarboxylic acid and Azopy = 4,4'-azopyridine), via a slow-diffusion method at room temperature. X-ray analysis authenticates the two-dimensional (2D)-layered framework of Cu-MOF. Topologically, this 2D-layered structure is assigned as a 4-connected unimodal net with sql topology. Further, nanostructured CuO is obtained via a simple precipitation method by employing Cu-MOF as a precursor. After analysis of their physicochemical properties through various techniques, both materials are used as surface modifiers of glassy carbon electrodes for a comparative electrochemical study. The results reveal a superior charge storage performance of CuO (244.2 F g-1 at a current density of 0.8 A g-1) with a high rate capability compared to Cu-MOF. This observation paves the pathway for the strategic design of high-performing supercapacitor electrode materials.
Richa Rajak, Ravinder Kumar, Shagufi Naz Ansari, Mohit Saraf, and Shaikh M. Mobin
Royal Society of Chemistry (RSC)
Mixed-metallic metal–organic frameworks (M-MOFs) are prepared through one-pot-synthesis or post-synthetic modification approaches and can be easily transformed into various composites/derivatives which offer promising supercapacitor properties.
Richa Rajak, Mohit Saraf, and Shaikh M. Mobin
American Chemical Society (ACS)
A new Na/Co-based heterometallic metal-organic framework, [Na2Co(SDCA)(μ2-OH)2(μ2-H2O)2(Azopy)]n (where Azopy = 4,4'-Azopyridine and SDCA = 2,5'-thiophenedicarboxylic acid) (1) with nanorod-shaped morphology was synthesized using mixed-ligand approach via slow-diffusion technique under ambient conditions. The crystal structure study demonstrates the proportion of Co(II) and Na(I) metal node to be 1:2 and the acquired coordination network reveals as a 3D architecture. Topologically, the 4-c Na(I) ion directs in situ assembly of 4-c SDCA linker and 6-c Co(II) ion, resulting in the formation of 4,4,6-c net with a topology named as smm3. Additionally, 1 was incorporated as a binder-free material for a glassy carbon electrode (1-GCE) to explore its supercapacitor performance, which reveals a high specific capacitance of 321.8 F g-1 at 4 A g-1 and notable rate performance (∼78.9% of initial capacitance up to 16 A g-1) as well as excellent cycling stability (retains 97.4% after 5000 cycles). The demonstrated strategy of employing different heterometallic clusters with mixed ligands markedly increases MOF's complexity and induces synergistic properties, which is highly favorable for electrochemical applications. Hence, the present approach can be extended to build a wide range of MOFs and synergistically enhanced electrochemical performance can be achieved.
Richa Rajak, Mohit Saraf, Sanjay K. Verma, Ravinder Kumar, and Shaikh M. Mobin
American Chemical Society (ACS)
A dysprosium metal-organic framework, {[Dy(μ2-FcDCA)1.5(MeOH)(H2O)]·0.5H2O}n (1), where FcDCA = 1,1'-ferrocene dicarboxylic acid, was prepared by slow-diffusion technique at room temperature. The crystal structure analysis of 1 by single-crystal X-ray diffraction reveals different binding modes of FcDCA linkers coordinated with Dy(III) metal ions, which forms continuous porous two-dimensional (2D) infinite framework. The resulting 2D layers are linked by π···π interactions to build three-dimensional (3D) supramolecular framework. Observably, this thermally stable 3D architecture was topologically simplified as a three-connected uninodal net with fes topology. Furthermore, the practical applicability of 1 was investigated as a fluorescence sensor for the sensitive detection of picric acid in aqueous medium with an impressive detection limit of 0.71 μM with quenching constant (KSV) quantified to be 8.55 × 104 M-1. The distinguished selectivity in the presence of other nitroaromatics suggests the possible incorporation of 1 in real-world futuristic diagnostic kits. Additionally, the electrochemical behavior of 1 exhibits reversible in nature attributed to the ferrocene/ferrocenium cation.
Mohit Saraf, Kaushik Natarajan, Anoop K Gupta, Pawan Kumar, Richa Rajak, and Shaikh M Mobin
IOP Publishing
Mohit Saraf, Richa Rajak, and Shaikh M. Mobin
Wiley
Richa Rajak, Akbar Mohammad, Prakash Chandra, and Shaikh M. Mobin
Wiley
Akbar Mohammad, Khursheed Ahmad, Richa Rajak, and Shaikh M. Mobin
Springer International Publishing
Richa Rajak, Mohit Saraf, and Shaikh M. Mobin
Royal Society of Chemistry (RSC)
A robust 2D heterostructure of heterobimetallic Na/Zn-MOF and rGO can be a promising alternative electrode material for next generation supercapacitors.
Akbar Mohammad, Shagufi Naz Ansari, Archana Chaudhary, Khursheed Ahmad, Richa Rajak, Mohd. Tauqeer, and Shaikh M. Mobin
Wiley
Akbar Mohammad, Khursheed Ahmad, Richa Rajak, and Shaikh M. Mobin
Wiley
Richa Rajak, Mohit Saraf, Akbar Mohammad, and Shaikh M. Mobin
Royal Society of Chemistry (RSC)
An inclined polycatenated Co-MOF (1) synthesized by a facile slow-diffusion technique shows excellent performance for supercapacitors and dye adsorption.
Khursheed Ahmad, Akbar Mohammad, Richa Rajak, and Shaikh M Mobin
IOP Publishing
TiO2 nanosheets were synthesized via solvothermal method and characterized using powder x-ray diffraction (PXRD), UV–vis spectroscopy, scanning electron microscopy (SEM) and energy dispersive x-ray (EDX) mapping. A binder free hydrazine sensor was fabricated by modifying the glassy carbon electrode (GCE) with TiO2 nanosheets, using simple drop casting method (GCE/TiO2). The modified GCE/TiO2 was employed for detection of hydrazine which exhibited a very high sensitivity of 70 μA mM−1 cm−2 with a limit of detection (LOD), 28 μM using cyclic voltammetry whereas a highest sensitivity 330 μA mM−1 cm−2 and LOD, 150 μM was obtained by employing square wave voltammetry.
Mohit Saraf, Richa Rajak, and Shaikh M. Mobin
Royal Society of Chemistry (RSC)
A hybrid (Cu-MOF/rGO) prepared by sonication mixing of a Cu-MOF and rGO shows high potential for both supercapacitors and nitrite sensors.
Kapil Tomar, Richa Rajak, Suresh Sanda, and Sanjit Konar
American Chemical Society (ACS)
Six porous metal–organic frameworks (MOFs), {[Ni(BTC)0.66(BPz)2]·2MeOH·4H2O}n (1), {[Co(BTC)0.66(BPz)2]·2MeOH·4H2O}n (2), {[Mn(BTC)0.66(BPz)2]·2MeOH·4H2O}n (3), {[Cd(BDC)(BPz)(H2O)]·2MeOH·DMF}n (4), {[Cd2(NH2-BDC)2(BPz)(H2O)]·MeOH·H2O·DMF}n (5), and {[Co(BDC)(BPz)(H2O)]}n (6) (where H3BTC = 1,3,5-benzenetricarboxylic acid, H2BDC = 1,4-benzenedicarboxylic acid, NH2-H2BDC = 2-amino-1,4-benzenedicarboxylic acid, and BPz = 3,3′,5,5′-tetramethyl-4,4′-bipyrazole), were obtained through a solvent diffusion technique and characterized. The networks exhibit a variety of topologies: 1, 2, and 3 are isostructural and possess octahedral and cuboctahedra type cages and exhibit 3,6-c binodal net having loh1 topology, 4 is a two-dimensional MOF having one-dimensional open channels with a 4-c uninodal net having sql topology, 5 exhibits a three-dimensional (3D) porous MOF having a 3,3,4,8-c net with a new topology having the name, skr1, whereas 6 discloses a 3D nonporous network which exhibits a 4-c uninodal net having C...