Inspired by recent experimental synthesis of two-dimensional cobalt bis(dithioline) (CoBHT) metal−organic surface (J. Am. Chem. Soc., 2015, 137, 118−121), herein, using first principle calculations, we have investigated the electronic and magnetic properties of two-dimensional BHT-based metal (M = Co, Fe, Mn, Cr)-organic frameworks (MBHT). Our detailed theoretical calculations predict that CoBHT, FeBHT, and MnBHT are planar ferromagnetic (FM) half-metals, whereas CrBHT is planar spinfrustrated kagome lattice antiferromagnetic (AFM) semimetal, a new state of matter referred as spin-liquid. These planar ferromagnetic half-metal materials are promising candidates for spintronic devices. Further, polluting gas such as CO can be detected by these MOFs as there is remarkable variation of electronic and magnetic properties after gas adsorption. Interestingly, these properties have been found to be a function of coordination environment of central metal atom, which is actually a coordinatively unsaturated (CUS) center. Square planar central metal atom changes its coordination geometry to distorted square pyramidal geometry (as metal atom protrude out of the square plane) to octahedral, after single and both side full coveraged gas adsorption, respectively. Especially, for their practical purposes in gas sensing, we have calculated the transport properties, taking the cobalt bis(dithioline) (Cobdt) molecule as an example. Unadsorbed (Cobdt) and coordinatively saturated bis-CO [Cobdt(CO) 2 ] adsorbed molecule provide remarkably distinct I−V responses, which becomes a signal for detection of CO gas. Moreover, Cobdt molecule shows the spin-filtering effect as it is half-metallic, thus Cobdt can be used as novel material for spintronic device fabrication. Therefore, the MOFs we have studied and Cobdt molecule can be used as potential materials for spintronic devices and for polluting gas sensing.
Presently, great attention is focused on the search for promising anode materials due to the rapid development of electronic products. In this study, by means of density functional calculations, we have predicted that a bilayer covalent triazine framework (CTF) may be a promising anode material for rechargeable lithium-ion batteries (LIBs). Our calculations reveal that lithium atoms can be preferably inserted into the interlayer spacing of the bilayer CTF. The calculations indicate charge transfer from Li atoms to the bilayer CTF. After lithium adsorption, the bilayer CTF undergoes a transition from a semiconductor to a metal, ensuring good electrical conductivity of the electrode material. Furthermore, the bilayer CTF can achieve a high theoretical specific capacity of 925.99 mAh/g and a moderately low diffusion barrier of 0.65 eV. Our calculated average open-circuit voltages (OCVs) lie in the range of 1.58–0.51 V, which are in between those of some typical anode materials. All of these calculations suggest that the bilayer CTF can be used as a potential anode material for LIBs.
Electrocatalytic water spliting is the most attractive route for hydrogen production, but the development of nonprecious, stable, and high-performance catalysts for hydrogen evolution reaction (HER) to replace the scarce platinum group metal-based electrocatalysts is still a challenging task for the scientific community. In this work, within the framework of density functional theory computations, we have predicted that a silicon and phosphorus co-doped bipyridine-linked covalent triazine framework, followed by substitution of bipyridine hydrogens at the P-site with fluorine atoms, may be a potential catalyst for HER. Our predicted model system (SiPF-Bpy-CTF) exhibits a very low band gap (7 meV), which may exhibit facile charge transfer kinetics during HER. Using the Gibbs free energy for the adsorption of atomic hydrogen ( ) as the key descriptor, we have found that our proposed model system (SiPF-Bpy-CTF) exhibits superior HER catalytic activity, with its being close to the ideal value (0 eV).
By using the state-of-the-art theoretical method, we have investigated the electronic structures of recently synthesized two-dimensional azine-linked covalent organic framework (ACOF-1). Our result indicates that ACOF-1 is a direct band gap semiconductor, suggesting useful application in nanoelectronics. Its one-dimensional (1D) structure also exhibits semiconducting properties. Furthermore, this azine-linked COF is found to be practically useful for selective sensing of nitroaromatics over nitroaliphatics. Lastly, our calculations reveal a more realizable way for using two tautomers of ATFG-COF, a derivative of ACOF-1, in conductance switching device by means of transport property calculation. Therefore, our present study may provide a guideline for multifunctionalities of azine-linked COF (ACOF-1).
By using a state-of-the-art theoretical method, we have investigated the electronic structure of a new class of nanocomposites, namely, porous graphene (PG)–fullerene (PG–fullerene) composite. We have utilized the porosity of PG to encapsulate the fullerene molecule into it and have investigated the efficacy of the PG–fullerene composite in solar cell and optoelectronic applications. Our study reveals that smaller sized composites show type-II band alignment, suggesting efficient charge separation upon photoexcitation. Hence, these composites may be utilized for designing solar cells. However, larger composites show type-I band alignment, thereby limiting their applications in solar cell. We further propose graphene antidot–fullerene composites with same pore structure as that of PG, which show type-II band alignment even for larger antidots. Qualitative analysis reveals that the electron injection rate as well as charge separation capability of antidot composites is larger than that of the PG composites. Hence, we can suggest that antidot composites are a better candidate for photovoltaic applications. We have also calculated the optical properties of PG–C60 composite systems and explore its applicability in designing optoelectronic devices.
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