Elí Sánchez-González

Water Adsorption Properties of NOTT-401 and CO2 Capture under Humid Conditions

The water-stable material NOTT-401 was investigated for CO2 capture under humid conditions. Water adsorption properties of NOTT-401 were studied, and their correlation with CO2 sequestration at different relative humidities (RHs) showed that the CO2 capture increased from 1.2 wt % (anhydrous conditions) to 3.9 wt % under 5% RH at 30 °C, representing a 3.2-fold improvement.

CO2 capture in a carbazole-based supramolecular polyhedron structure: the significance of Cu(II) open metal sites

A crystalline, porous Metal–Organic Polyhedron (MOP) 4 was readily assembled starting from 9H-carbazole-3,6-dicarboxylic acid, which was synthesised in only three steps. The single crystal X-ray diffraction analysis of the resulting supramolecule evidenced voids that were occupied by coordinated as well as uncoordinated solvent molecules from the solvothermal reaction. Careful analysis of its desolvation process, activating the sample at 150 °C and 10−5 bar (followed by FTIR), evidenced that all solvents were completely removed, leaving an empty but nevertheless crystalline MOP with coordinatively-unsaturated Cu(II) sites that was studied for gas adsorption using N2 at 77 K, and CO2 at 196 K. Notably, carbon dioxide was found to be strongly adsorbed in the activated 4 (12.1 mmol g−1, 53.2 wt%) with a molar enthalpy of adsorption of ΔH = 65.12 kJ mol−1, revealing a great selectivity over nitrogen, which in turn showed negligible uptake under the same activation conditions. In situ Raman experiments demonstrated the direct interaction of CO2 molecules and coordinatively-unsaturated Cu(II) sites within 4.

Synthesis of vanillin via a catalytically active Cu(II)-metal organic polyhedron

Crystalline Cu(II)-MOP 1 was employed for the first time in the catalytic conversion of trans-ferulic acid to vanillin. The generation of uncoordinated Cu(II) metal sites within MOP 1 by activation as well as sonication, revealed its catalytic potential that afforded a reaction yield of 60%. Complementary cyclic voltammetry experiments (CVs) demonstrated the formation of the complex Cu–H2O2, which supported the reaction mechanism proposed here.

Confinement of alcohols to enhance CO2 capture in MIL-53(Al)

CO2 capture of MIL-53(Al) was enhanced by confining MeOH and i-PrOH within its micropores. Compared to MIL-53(Al), results showed an approximately 1.3 fold increase in CO2 capture capacity (kinetic isothermal CO2 adsorption experiments), via confining small amounts of both alcohols. Adsorption–desorption properties are investigated for MeOH and i-PrOH and the enthalpy of adsorption, for MeOH and i-PrOH, was measured by differential scanning calorimetry (DSC): ΔH = 50 and 56 kJ mol−1, respectively. Regeneration (CO2 adsorption–desorption cycles) of the sample MeOH@MIL-53(Al) exhibited a loss on the CO2 capacity of only 6.3% after 10 cycles and the desorption is accomplished by only turning the CO2 flow off. Static CO2 adsorption experiments (at 196 K) demonstrated a 1.25-fold CO2 capture increase (from 7.2 mmol g−1, fully activated MIL-53(Al) to 9.0 mmol g−1, MeOH@MIL-53(Al)). The CO2 enthalpy of adsorption for MIL-53(Al) and Me@OHMIL-53(Al) were estimated to be ΔH = 42.1 and 50.3 kJ mol−1, respectively. Computational calculations demonstrated the role of the hydrogen bonds formed between CO2 molecules and confined MeOH and i-PrOH molecules, resulting in the enhancement of the overall CO2 capture.

Transient Porosity in Densely Packed Crystalline Carbazole–(p-Diethynylphenylene)–Carbazole Rotors: CO2 and Acetone Sorption Properties

We report for the first time the high sorption properties of a molecular rotor with no permanent voids or channels in its crystal structure. Such crystalline phase originates from THF, DCM, or the irreversible desolvation of entrapped benzene molecules. From these, the benzene in its solvate form acts as rotation stopper, as supported by dynamic characterization using solid-state 2H NMR experiments. In the solvent-free form, the diffusion of small quantities of iodine vapors caused a significant change in the intramolecular rotation, increasing the known activation energy to rotation from 8.5 to 10.6 kcal mol-1. Notably, those results paved the way for the discovery of the high CO2 uptake (201.6 cm3 g-1 at 196 K, under 1 atm) and acetone (5 wt %), a sorption property that was attributed to both, the restriction of the molecular rotation at low temperatures and the flexibility of the molecular axle made of conjugated p-(ethynylphenylene), surrounded by carbazole.

Highly reversible sorption of H2S and CO2 by an environmentally friendly Mg-based MOF

Mg-CUK-1, an ecologically friendly material synthesised in water is found to be a high-capacity, highly reversible adsorbent for acidic gases including H2S and CO2. Furthermore, Mg-CUK-1 is demonstrated to retain long-range crystallinity upon sorption cycling; its sorption performance is maintained over multiple cycles, even in the presence of high relative humidity (95%). Reversible H2S adsorption by Mg-CUK-1 is rare among MOFs studied for this purpose to date. The joint experimental and computational studies presented here show that Mg-CUK-1 is an effective solid adsorbent for applications in the field of acid gas capture, an application that is highly relevant for the purification of many industrial gas streams.