Exceptional High and Reversible Ammonia Uptake by Two Dimension Few-layer BiI3 Nanosheets

Improved NH3 Uptake of a Macromolecule-Metal Complex Constructed with Dual Polymeric Ligands and M(II)

MOFs are considered as efficient NH3 adsorbents for their high capacity but are accompanied by the collapse of MOFs. In this work, macromolecule-metal complexes (MMCs), which could provide metal sites like MOFs, were developed for reversible NH3 uptake with high capacity with the assistance of the polymeric ligands. Based on the tunable structure of MMCs, the role of the polymeric ligands and metallic center was investigated. Thereinto, MMCs-3 with dual polymeric ligands presented higher NH3 adsorption capacity and reversibility of adsorbents compared with MMCs containing a single polymeric ligand (MMCs-1 and MMCs-2). Combined with the NH3 adsorption test, characterization of FT-IR, UV-vis, EPR spectroscopy, NH3-TPD measurement, and the DFT calculations, it was found that the neutral polymeric ligands PVIm contributed to improve the stability of MMCs-3 under a NH3 atmosphere for the tough networks of PVIm-M(II), while the polymeric ligands with a carboxylate anion together with M(II) enhanced the NH3 capacity for the feasible coordination of a carboxylate anion with M(II). The mechanism of NH3 uptake by PVIm-Co-PVBA was proposed that the NH3 was fixed through the coordination with Co(II) along with the departure of PVBA and the following hydrogen bonding interaction with PVBA, while the coordination between PVIm and Co(II) was not destroyed. Thus, MMCs-3 with dual polymeric ligands presented a higher NH3 uptake capacity and stability. Optimally, PVIm-M-PVBA with the metal center of Co(II), Cu(II), and Ni(II) were obtained with a high capacity of 20.8-23.7 NH3 mmol/g at 25 °C and 1 bar and a high selectivity of NH3 over CO2 (54.9-99.9) and N2 (73.0-187.6) through the breakthrough measurement with a gas mixture of 0.2% NH3, 2% CO2, and 99.6% N2 at 25 °C.

Interaction of Nucleic Acids with Metal-Organic Framework Nanosheets by Fluorescence Spectroscopy and Molecular Dynamics Simulations

The integration of nanomaterials and nucleic acids has attracted great attention in various research fields, especially biomedical applications. Designing two-dimensional nanomaterials and studying the mechanism of their interaction with nucleic acids are still attractive tasks. Herein, we designed and prepared a class of ultrathin two-dimensional metal-organic framework (MOF) nanosheets, named Zr-BTB MOF nanosheets, composed of Zr-O clusters and 1,3,5-benzenetribenzoate by a bottom-up synthesis strategy. The Zr-BTB MOF nanosheets possessed inherent excellent performance such as a high specific surface area, porosity, and biocompatibility. In addition, we clarified the interaction difference between the Zr-BTB MOF nanosheets and fluorophore-labeled double-stranded DNA and single-stranded DNA via molecular dynamics simulations and fluorescence measurement. Through molecular dynamics simulations, specific interactions between DNA and nanosheets such as forces, binding energies, and binding modes were deeply analyzed and clearly presented. Based on the affinity difference, the system showed the biosensing potential for target DNA detection with considerable specificity, sensitivity, and linearity. Our research results presented the Zr-BTB MOF nanosheet as a platform for nucleic acid detection, showing the potential for hybridization-based biosensing and related biological applications.

Electrospun Ta-MOF/PEBA Nanohybrids and Their CH4 Adsorption Application

For the first time, biocompatible and biodegradable Ta-metal organic framework (MOF)/polyether block amide (PEBA) fibrous polymeric nanostructures were synthesized by ultrasonic and electrospinning routes in this study. The XRD peaks of products were wider, which is due to the significant effect of the ultrasonic and electrospinning methods on the final product. The adsorption/desorption behavior of the nanostructures is similar to that of the third type of isotherm series, which showed mesoporous behavior for the products. The sample has uniform morphology without any evidence of agglomeration. Since the adsorption and trapping of gaseous pollutants are very important, the application of the final Ta-MOF/PEBA fibrous polymeric nanostructures was investigated for CH4 adsorption. In order to achieve the optimal conditions of experiments and also systematic studies of the parameters, fractional factorial design was used. The results showed that by selecting temperature 40°C, time duration 35 min, and pressure 3 bar, the CH4 gas adsorption rate was near 4 mmol/g. Ultrasonic and electrospinning routes as well as immobilization of Ta-MOF in the PEBA fibrous network affect the performance of the final products for CH4 gas adsorption.

High Gravimetric and Volumetric Ammonia Capacities in Robust Metal-Organic Frameworks Prepared via Double Postsynthetic Modification

Ammonia is a promising energy vector that can store the high energy density of hydrogen. For this reason, numerous adsorbents have been investigated as ammonia storage materials, but ammonia adsorbents with a high gravimetric/volumetric ammonia capacity that can be simultaneously regenerated in an energy-efficient manner remain underdeveloped, which hampers their practical implementation. Herein, we report Ni_acryl_TMA (TMA = thiomallic acid), an acidic group-functionalized metal-organic framework prepared via successive postsynthetic modifications of mesoporous Ni₂Cl₂BTDD (BTDD = bis(1H-1,2,3,-triazolo [4,5-b],-[4',5'-i]) dibenzo[1,4]dioxin). By virtue of the densely located acid groups, Ni_acryl_TMA exhibited a top-tier gravimetric ammonia capacity of 23.5 mmol g^-1 and the highest ammonia storage of 0.39 g cm^-3 at 1 bar and 298 K. The structural integrity and ammonia storage capacity of Ni_acryl_TMA were maintained after ammonia adsorption-desorption tests over five cycles. Temperature-programmed desorption analysis revealed that the moderate strength of the interaction between the functional groups and ammonia significantly reduced the desorption temperature compared to that of the pristine framework with open metal sites. The structures of the postsynthetic modified analogues were elucidated based on Pawley/Rietveld refinement of the synchrotron powder X-ray diffraction patterns and van der Waals (vdW)-corrected density functional theory (DFT) calculations. Furthermore, the ammonia adsorption mechanism was investigated via in situ infrared and vdW-corrected DFT calculations, revealing an atypical guest-induced binding mode transformation of the integrated carboxylate. Dynamic breakthrough tests showed that Ni_acryl_TMA can selectively capture traces of ammonia under both dry and wet conditions (80% relative humidity). These results demonstrate that Ni_acryl_TMA is a superior ammonia storage/capture material.

Fabrication of a Nickel Ferrite/Nanocellulose-Based Nanocomposite as an Active Sensing Material for the Detection of Chlorine Gas

Chlorine gas is extensively utilised in industries as both a disinfectant and for wastewater treatment. It has a pungent and irritating odour that is comparable with that of bleach and can cause serious health issues such as headaches and breathing difficulties. Hence, efficiently, and accurately monitoring chlorine gas is critical to ensure that no undesirable incidents occur. Due to its remarkable characteristics, numerous researchers have explored the potential of ferrite nanoparticles as a sensing material for chlorine gas detection. Among several ferrite nanoparticles, nickel ferrite (NiFe₂O₄) is extensively studied as an inverse spinel structured magnetic material that may be ideal for sensing applications. However, the magnetic characteristics of NiFe₂O₄ cause agglomeration, which necessitates the use of a substrate for stabilisation. Therefore, nanocellulose (NC), as a green and eco-friendly substrate, is ideal for stabilising bare nickel ferrite nanoparticles. In a novel experiment, nickel ferrite was loaded onto NC as a substrate using in situ deposition. The structure was confirmed by X-ray Diffraction (XRD) analysis, while elemental composition was verified by Energy dispersive X-ray (EDX) analysis. Gas sensing properties were determined by evaluating sensitivity as a function of various regulating factors, such as the amount of nickel ferrite, gas concentration, repeatability, and reusability. In the evaluation, 0.3 g nickel ferrite showed superior response and sensitivity than those of other samples. The achieved response time was around 40 s, while recovery time was about 50 s. This study demonstrates the potential of a nickel ferrite/nanocellulose-based nanocomposite to efficiently monitor chlorine gas.

A model of FeN-decorated BeO layer particle for CO gas adsorption

Carbon monoxide (CO) is known as a deathful gas produced by burning of hydrocarbons in a lack of enough oxygen, in which breathing CO leads to serious issues on human life health quality. Therefore, adsorption of CO gas is an essential task for diagnosis or removal of this dreadful gas in environment. To do this, a HEME-like model of iron-nitrogen-doped beryllium oxide (FeNBeO) monolayer was investigated for adsorbing CO gas by performing density functional theory (DFT) calculations. Two models were obtained for this process, in which relaxation of CO with C-head or O-head towards Fe region of monolayer. The results indicated that the formation of FeNBeO-CO model could be achieved more favorable than the formation of FeNBeO-OC model. The obtained optimized geometers and energies all approved this achievement for favorability of FeNBeO-CO model formation. Moreover, molecular orbital based electronic features indicated variations of such features for the models upon adsorption of CO substance, in which the models could be detectable in a sensor function for the existence of CO gas in the environment. As a consequence, the investigated FeNBeO monolayer could be proposed useful for adsorption of CO gas at least for the CO deathful gas diagnosis purposes.

Selective adsorption and dissociation of NO, NO2, and N2O molecules on Si-doped haeckelite boron nitride nanotube: an investigation for sensitive molecular sensors and catalysts

The current study describes the investigation of the adsorption NO, N₂O, and NO₂ on haeckelite boron nitride nanotube doped with Si (Si-doped haeck-BNNT) by means of density functional theory calculation (DFT). The obtained results confirmed the energetic stability of the optimized geometries and revealed that the adsorption of the gas molecules with the nanotube sidewall is a spontaneous process. The calculated work function of Si-doped haeck-BNNT in the presence of gas molecules is greater than that of a bare Si-doped haeck-BNNT sheet. The energy gap of the Si-doped haeck-BNNT is sensitive to the adsorption of the gas molecules, which implies possible future applications in gas sensors. For most of the adsorption configurations studied, the adsorption energies for the Si_B-doped haeck-BNNT are higher than those for Si_N-doped haeck-BNNTones. The N₂O gas molecule is totally dissociated into N₂ and O species through the adsorption process, while the other gas molecules retain their molecular forms. Thus, the Si_N-doped haeck-BNNT is a likely catalyst for dissociation of the N₂O gas molecule. Our findings divulge promising potential of the doped haeck-BNNT as a highly sensitive molecular sensor for NO and NO₂ detection and a catalyst for N₂O dissociation.

Tailoring Multiple Sites of Metal-Organic Frameworks for Highly Efficient and Reversible Ammonia Adsorption

The structural diversity and designability of metal-organic frameworks (MOFs) make these porous materials a strong candidate for NH₃ uptake. However, to achieve a high NH₃ capture capacity and good recyclability of MOFs at the same time remains a great challenge. Here, a multiple-site ligand screening strategy of MOFs is proposed for highly efficient and reversible NH₃ uptake for the first time. Based on the optimized DFT results for various possible ligands, pyrazole-3,5-dicarboxylate with multiple sites was screened as the best ligand to construct robust MOF-303(Al) with Al³⁺. It is experimentally found that the NH₃ adsorption capacity of MOF-303(Al) is as high as 19.7 mmol g^-1 at 25.0 °C and 1.0 bar, and the NH₃ capture is fully reversible and no clear loss of capture capacity is observed after 20 cycles of adsorption-desorption. Various spectral studies verify that the superior NH₃ capacity and excellent recyclability of MOF-303(Al) are mainly attributed to the hydrogen bonding interactions of NH₃ with multiple sites of MOF-303(Al).

Substitution effects via aromaticity, polarizability, APT, AIM, IR analysis, and hydrogen adsorption in C20-nTin nanostructures: a DFT survey

In this paper, the substitution effects of titanium heteroatom(s) on aromaticity, the average isotropic polarizability (< α >), the atomic polar tensor (APT) charge, the electrostatic potential (ESP) map, and the atoms in molecule (AIM) analysis along with infrared (IR) spectroscopy of C₂₀ fullerene and its C_20-nTi_n derivatives (n = 1-5) are probed via density functional theory (DFT). The nucleus-independent chemical shifts (NICS) specify that substitution effect causes more aromaticity character of the optimized heterofullerenes than benzene molecule and higher APT charge distribution upon surfaces of them than pure cage. The highest negative and positive APT charge distribution on carbons of C₁₅Ti₅ and titanium substitutions of C₁₆Ti_4-2 implies that these sites can be attacked more readily by electrophilic and nucleophilic regents, respectively. We are very pleased to state that isolating the Ti-Ti single bonds by intermediacy of one or two C atoms is an applicable strategy for attaining the highest APT charge distribution on Ti atoms of C₁₆Ti_4-2 as suitable hydrogen storage. AIM analysis of the studied C_20-nAl_n derivatives signifies the highest electron density (ρ (r)) of 0.294 a.u. and the highest positive Laplacian of electron density (∇²ρ (r)) of 0.190 a.u., at bond critical points (BCPs) of C-Ti bond in the most stable C₁₉Ti₁ species. This heterofullerene shows the lowest < α > between the studied structures. IR spectroscopy shows that exclusive of C₁₆Ti_4-1 (as transition state), the other optimized hollow cages (as global minima) have no imaginary frequency.

Quantum chemical studies of mercaptan gas detection with calcium oxide nanocluster

The electronic sensitivity and adsorption behavior for mercaptan natural gas of a Ca₁₂O₁₂ nanocluster were studied via ab initio computations. To be more specific, to fully grasp the influence of mercaptan molecules on the chemical and electronic features of Ca₁₂O₁₂ nanocluster, some parameters, namely, charge transfer of natural bond orbital, molecular electrostatic potential, binding energies, and frontier molecular orbitals, are computed. The interaction between CH₄S molecule and calcium atoms of Ca₁₂O₁₂ nanocluster through the sulfur head is strong. This strong interaction leads to a considerable transfer of charge from CH₄S to the nanocluster. After mercaptan adsorption, the existing energy gap between two levels, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the nanostructure, dropped by 2.21 eV, illustrating that the dissociation process has extensively increased the electrical conductance of nanostructure. This electrical signal can help to detect CH₄S molecules. Moreover, it could be concluded that Ca₁₂O₁₂ nanocluster has a short recovery time. In addition, solvent considerably influences the geometry factors and electronic features of CH₄S/Ca₁₂O₁₂ complexes, and the interactions between species are significantly weaker in the aqueous medium compared with those in the vacuum.

Alkoxysulfenylation of alkenes: development and recent advances

Among the wide variety of synthetic transformations of inexpensive and abundant feedstock alkenes, vicinal difunctionalization of carbon-carbon double bonds represent one of the most powerful and effective strategies for the introduction of two distinct functional groups into target compounds in a one-pot process. In this context, the direct alkoxysulfenylation of alkenes has emerged as an elegant method to construct valuable β-alkoxy sulfides in an atom- and pot-economic manner utilizing readily accessible starting materials. Here, we review the available literature on this appealing research topic by hoping that it will be beneficial for eliciting further research and thinking in this domain.

Recent trends in dehydroxylative trifluoro-methylation, -methoxylation, -methylthiolation, and -methylselenylation of alcohols

This review studies on the direct dehydroxylative trifluoromethylation, trifluoromethoxylation, trifluoromethylthiolation, and trifluoromethylselenylation of alcohols.