Molecular Dynamics Simulation of the Energetics and Structure of Layered Double Hydroxides Intercalated with Carboxylic Acids

Abstract

Molecular dynamics (MD) simulation of the Mg/Al (3:1) layered double hydroxide (LDH), hydrotalcite (HT), containing the monocarboxylic acids formate, acetate, and propanoate as the charge balancing interlayer anions provides new molecular-scale insight into the interlayer structure, hydrogen bonding, and energetics of hydration and consequent swelling of LDH compounds containing organic molecules and biomolecules with carboxylate functional groups. As for citrate-HT (Kumar, P. P.; Kalinichev, A. G.; Kirkpatrick, R. J. J. Phys. Chem. B 2006, 110, 3841), the hydration energy of these systems as a function of water content has no distinct minima, indicating the absence of energetically well-defined structural states with specific water contents. The hydration energies, however, approach the energy of bulk liquid water at lower water contents than for citrate-HT, suggesting that synthesis strategies involving delamination of the hydroxide layers in water are likely to be more successful using starting compounds containing larger molecules with multiple carboxylate groups. This result is consistent with recent experimental observations of the delamination of lactate-HT (Hibino, T.; Kobayashi, W.

Structural Arrangements of Isomorphic Substitutions in Smectites: Molecular Simulation of the Swelling Properties, Interlayer Structure, and Dynamics of Hydrated Cs–Montmorillonite Revisited with New Clay Models

“…In order to quantify the thermodynamics of hydration and swelling for three different Cs−montmorillonite models, we calculated the hydration energy, immersion energy, 27,36,40,41,[96][97][98]100 and the isosteric heat of adsorption 27 at each of the hydration states. The hydration energy (ΔU) evaluates the energy change associated with water uptake by the dry clay, and can be calculated using the generic formula:…”

Theoretical studies of the interaction of terephthalate anion in MgAl-layered double hydroxides

“…Due to the versatility for construction of the structure, the LDHs represent a class of materials with interesting and potentially useful properties (Vucelic et al, 1995), (Nishimura et al, 2013). Also, by reason of their capacity of expansion along the c vector, LDHs are suitable to intercalate a large number of organic species, making them useful in many fields such as medicine, photochemistry, molecular separation, catalysis, and anion-exchange (Kloprogge & Frost, 1999), (Kumar et al, 2007), (Costa et al, 2010), (Costa et al, 2011), (Costantino et al, 2013). Although the most common anion is carbonate, terephthalate (TA) has been widely studied most because of its use as swelling agent, to assist the incorporation of bulkier anions (Drezdzon, 1988), (Vucelic et al, 1995), and also because its relatively rigid nature enables studies on the dynamics of interlayer anions, both by spectroscopic, and computational studies (Greenwell et al, 2010).…”

Interaction of Natural Organic Matter with Layered Minerals: Recent Developments in Computational Methods at the Nanoscale

“…In simulating the adsorption of small alcohol and thiol compounds onto Al(OH) 3 , Greathouse et al [50] showed that trends in simulated adsorption enthalpies were in excellent agreement with experiment ( Figure 2). MD simulations have also been used to study the adsorption of small organic molecules [51][52][53][54], polymers [55][56][57], (bio)organic acids [58][59][60], or entire nucleic acid strands [61][62][63][64][65] onto mineral surfaces. The latter simulations have been particularly noteworthy owing to the size and complexity of the biomolecules studied, with Thyveetil et al [61] using a high performance computing grid to simulate hydrated whole deoxyribonucleic acid (DNA) plasmids of 480 base pairs within a periodic mineral cell of 50 nm lateral dimensions, and containing 1,157,038 atoms in total.…”