Mechanistic Understanding of Sieving Lithium Ions Using a Biobased Sorbent Technology for Sustainable Lithium Reclamation and Cleansing Brines.

Low-cost environmentally benign materials that can be produced in a large scale to extract lithium from brine resources could drive the lithium market toward a clean technology with high lithium recovery and production. Herein, we have investigated the utilization of a novel, environmentally benign, and low-cost biobased sorbent for the extraction of lithium from lithium-rich solutions. This biobased molecular sieving sorbent, iron(III)-tannate (Fe(III)-TA), belongs to a novel class of coordination polymer frameworks derived from a natural polyphenol-tannic acid (TA)-coordinated with iron(III) metal cations. Its lithium adsorption and kinetic isotherm studies conducted using lithium-rich aqueous solutions confirm the sorbent's dual function for lithium sieving via physisorption, chemisorption, and mass transfer diffusion processes. The adsorption equilibrium and kinetic isotherm models combined with the external and internal mass transfer diffusion models reveal a mechanistic pathway for lithium-ion adsorption. Aiding by forming a fluid film for external mass transfer diffusion of lithium ions, analytes adsorb onto the sorbent surface via physisorption and chemisorption followed by the internal mass transfer diffusion, occupying lithium ions in the sorbent's pores. The lithium adsorption efficiency studies conducted for brines with different concentrations of interference alkali and alkaline cations evidence that the sorbent's affinity for lithium ions strongly depends on the analyte concentration. The results evidence that the sorbent has the ability to lower the brine's salinity and significantly reduces the ratios of Mg/Li and Ca/Li by 4-fold and 10-fold, respectively, yielding lithium-rich solutions. Thus, implementing this innovative biobased sorbent technology as an add-in step into traditional lithium extraction and refining processes, one can design a cost-effective pathway to yield lithium-rich leachate by reducing the Mg/Li and Ca/Li ratio. Nonetheless, the present work demonstrates that Fe(III)-tannate is an effective multifunctional sorbent for sieving lithium from lithium-rich aqueous solutions as well as for desalinating brine resources to recover usable water. Thus, this biobased sorbent offers the possibility of effective application of lithium reclamation and remediation of brine, mitigating the environmental impact of brine discharge and large volume of freshwater usage for lithium extraction and refining.

Molecular magnetism in nanodomains of isoreticular MIL-88(Fe)-MOFs.

Molecular magnetism in nanodomains of three isoreticular MIL-88(Fe) analogues is studied and reported. Microstructures of isoreticular extended frameworks of MIL-88B, MIL-88C, and the interpenetrated analogue of MIL-88D, i.e., MIL-126, with the trigonal prismatic 6-c acs net are synthesized by linking Fe3O inorganic cluster units with organic carboxylate linkers - benzene-1,4-dicarboxylic acid (BDC), 2,6-naphthalene dicarboxylic acid (NDC), and biphenyl-4,4'-dicarboxylic acid (BPDC), using a controlled solvent driven self-assembly process followed by a solvothermal method. The powder XRD traces are matched with the simulated diffraction patterns generated from their corresponding crystal structures, revealing the hexagonal symmetry for MIL-88B and MIL-88C, and the tetragonal symmetry for MIL-126. The elemental composition analysis confirms the empirical formula to be Fe3O(L)3 where L is the organic linker, supporting the formation of isoreticular MIL-88(Fe)-MOFs with MIL-88 topology. The morphologies of microstructures analyzed by SEM and TEM exhibit long spindle shaped rods with a core and a shell-like architecture for MIL-88B and MIL-88 C whereas MIL-126 shows cubic-shaped microstructures. The M-T plots confirm their blocking temperatures, TB, to be 60 K, 50 K, and 40 K for MIL-88B, MIL-88C, and MIL-126, respectively. The M-H plots reveal their magnetic response to be ferromagnetic at 10 K with the coercivities, HC, ranging from 250 G to 180 G. The gradual decrease in the TB and HC correlates with the nanocrystals' domain size, which decreases from MIL-88B to MIL-88C to MIL-126. Their phase transition from the ferromagnetic state to the short range ordering of the superparamagnetic state is observed in the temperature range of 100 K to 300 K. At T > TB, nanocrystals of all three MIL-88 microstructures act as a single-magnetic domain, owing to their shape anisotropy and finite-dimensionality. The electron density distribution and the spin density state modeled for each MIL-88 analogue exhibit localized electron density and spin density on Fe3O clusters, indicating the short range magnetic moment ordering in triangular metal oxide nodes with no extended magnetic cooperativity from their organic linkers. The short-range ordering of superparamagnetism in MIL-88(Fe)-MOFs suggests their further study as porous molecular-based magnets.

Analytical Approach to Screen Semiconducting MOFs Using Bloch Mode Analysis and Spectroscopic Measurements.

A rapid and simple analytical approach is developed to screen the semiconducting properties of metal organic frameworks (MOFs) by modeling the band structure and predicting the density of state of isoreticular MOFs (IRMOFs). One can consider the periodic arrangement of metal nodes linked by organic subunits as a 1D periodic array crystal model, which can be aligned with any unit-cell axis included in the IRMOF's primitive cubic lattice. In such a structure, each valence electron of a metal atom feels the potential field of the entire periodic array. We allocate the 1D periodic array in a crystal unit cell to three IRMOFs-n (n = 1, 8, and 10) of the Zn4O(L)3 IRMOF series and apply the model to their crystal lattices with unit-cell constants a = 25.66, 30.09, and 34.28 Å, respectively. By solving Schrödinger's equation with a Kronig-Penney periodic potential and fitting the computed energy spectra to IRMOFs' experimental spectroscopic data, we model electronic band structures and obtain densities of state. The band diagram of each IRMOF reveals the nature of its electronic structures and density of state, allowing one to identify its n- or p-type semiconducting behavior. This novel analytical approach serves as a predictive and rapid screening tool to search the MOF database to identify potential semiconducting MOFs.

Novel biodegradable low-κ dielectric nanomaterials from natural polyphenols.

Biodegradable natural polymers and macromolecules for transient electronics have great potential to reduce the environmental footprint and provide opportunities to create emerging and environmentally sustainable technologies. Creating complex electronic devices from biodegradable materials requires exploring their chemical design pathways to use them as substrates, dielectric insulators, conductors, and semiconductors. While most research exploration has been conducted using natural polymers as substrates for electronic devices, a very few natural polymers have been explored as dielectric insulators, but they possess high dielectric constants. Herein, for the first time, we have demonstrated a natural polyphenol-based nanomaterial, derived from tannic acid as a low-κ dielectric material by introducing a highly nanoporous framework with a silsesquioxane core structure. Utilizing natural tannic acid, porous "raspberry-like" nanoparticles (TA-NPs) are prepared by a sol-gel polymerization method, starting from reactive silane unit-functionalized tannic acid. Particle composition, thermal stability, porosity distribution, and morphology are analyzed, confirming the mesoporous nature of the nanoparticles with an average pore diameter ranging from 19 to 23 nm, pore volume of 0.032 cm3 g-1 and thermal stability up to 350 °C. The dielectric properties of the TA-NPs, silane functionalized tannic acid precursor, and tannic acid are evaluated and compared by fabricating thin film capacitors under ambient conditions. The dielectric constants (κ) are found to be 2.98, 2.84, and 2.69 (±0.02) for tannic acid, tannic acid-silane, and TA-NPs, respectively. The unique chemical design approach developed in this work provides us with a path to create low-κ biodegradable nanomaterials from natural polyphenols by weakening their polarizability and introducing high mesoporosity into the structure.

A sol-gel synthesis to prepare size and shape-controlled mesoporous nanostructures of binary (II-VI) metal oxides.

A base-catalyzed sol-gel approach combined with a solvent-driven self-assembly process at low temperature is augmented to make manganese oxide (Mn3O4), copper oxide (CuO), and magnesium hydroxide (Mg(OH)2) nanostructures with size- and shape-controlled morphologies. Nanostructures of Mn3O4 with either hexagonal, irregular particle, or ribbon shape morphologies with an average diameter ranged from 100 to 200 nm have been prepared in four different solvent types. In all morphologies of Mn3O4, the experimental XRD patterns have indexed the nanocrystal unit cell structure to triclinic. The hexagonal nanoparticles of Mn3O4 exhibit high mesoporocity with a BET surface area of 91.68 m2 g-1 and BJH desorption average pore diameter of ∼28 nm. In the preparation of CuO nanostructures, highly nanoporous thin sheets have been produced in water and water/toluene solvent systems. The simulated XRD pattern matches the experimental XRD patterns of CuO nanostructures and indexes the nanocrystal unit cell structure to monoclinic. With the smallest desorption total pore volume of 0.09 cm3 g-1, CuO nanosheets have yielded the lowest BET surface area of 18.31 m2 g-1 and a BHJ desorption average pore diameter of ∼16 nm. The sol of magnesium hydroxide nanocrystals produces highly nanoporous hexagonal nanoplates in water and water/toluene solvent systems. The wide angle powder XRD patterns show well-defined Bragg's peaks, indexing to a hexagonal unit cell structure. The hexagonal plates show a significantly high BET surface area (72.31 m2 g-1), which is slightly lower than the surface area of Mn3O4 hexagonal nanoparticles. The non-template driven sol-gel synthesis process demonstrated herein provides a facile method to prepare highly mesoporous and nanoporous nanostructures of binary (II-IV) metal oxides and their hydroxide derivatives, enabling potential nanostructure platforms with high activities and selectivities for catalysis applications.