Confined benzene within InOF-1: contrasting CO2 and SO2 capture behaviours.

The confinement of small amounts of benzene in InOF-1 (Bz@InOF-1) shows a contradictory behavior in the capture of CO2 and SO2. While the capture of CO2 is increased 1.6 times, compared to the pristine material, the capture of SO2 shows a considerable decrease. To elucidate these behaviors, the interactions of CO2 and SO2 with Bz@InOF-1 were studied by DFT periodical calculations postulating a plausible explanation: (a) in the case of benzene and CO2, these molecules do not compete for the preferential adsorption sites within InOF-1, providing a cooperative CO2 capture enhancement and (b) benzene and SO2 strongly compete for these preferential adsorption sites inside the MOF material, reducing the total SO2 capture.

Confined toluene within InOF-1: CO2 capture enhancement.

The toluene adsorption properties of InOF-1 are studied along with the confinement of small amounts of this non-polar molecule revealing a 1.38-fold increase in CO2 capture, from 5.26 wt% under anhydrous conditions to 7.28 wt% with a 1.5 wt% of pre-confined toluene at 298 K. The InOF-1 affinity towards toluene was experimentally quantified by ΔH ads (-46.81 kJ mol-1). InOF-1 is shown to be a promising material for CO2 capture under industrial conditions. Computational calculations (DFT and QTAIM) and DRIFTs in situ experiments provided a possible explanation for the experimental CO2 capture enhancement by showing how the toluene molecule is confined within InOF-1, which constructed a "bottleneck effect".

Confined methanol within InOF-1: CO2 capture enhancement.

The CO2 capture performance of InOF-1 was optimised by confining small amounts of MeOH within its micropores (MeOH@InOF-1). In comparison with fully activated InOF-1, MeOH@InOF-1 shows a 1.30 and 4.88-fold increase in CO2 capture capacity for kinetic and static isothermal CO2 adsorption experiments respectively. Density functional theory calculations coupled with forcefield based-Monte Carlo simulations revealed that such an enhancement is assigned to an increase of the degree of confinement felt by the CO2 molecules resulting from the formation of a lump at the vicinity of the µ2-OH groups since MeOH strongly interacts with these adsorption sites and is thus highly localized in this region.

Structure stability of HKUST-1 towards water and ethanol and their effect on its CO2 capture properties.

Water and ethanol stabilities of the crystal structure of the Cu-based metal-organic framework (MOF) HKUST-1 have been investigated. Vapour (water and ethanol) sorption isotherms and cyclability were measured by a dynamic strategy. The ethanol sorption capacity of HKUST-1 at 303 K remained unchanged contrasting water sorption (which decreased along with the sorption experiment time). Considering the binding energy of each sorbate with the open Cu(ii) sites, obtained by the use of diffusion coefficients, we showed the superior crystal stability of the HKUST-1 framework towards ethanol. Finally, a small quantity of ethanol (pre-adsorbed) slightly enhanced CO2 capture without crystal structure degradation.

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.

HKUST-1 as a Heterogeneous Catalyst for the Synthesis of Vanillin.

Vanillin (4-hydoxy-3-methoxybenzaldehyde) is the main component of the extract of vanilla bean. The natural vanilla scent is a mixture of approximately 200 different odorant compounds in addition to vanillin. The natural extraction of vanillin (from the orchid Vanilla planifolia, Vanilla tahitiensis and Vanilla pompon) represents only 1% of the worldwide production and since this process is expensive and very long, the rest of the production of vanillin is synthesized. Many biotechnological approaches can be used for the synthesis of vanillin from lignin, phenolic stilbenes, isoeugenol, eugenol, guaicol, etc., with the disadvantage of harming the environment since these processes use strong oxidizing agents and toxic solvents. Thus, eco-friendly alternatives on the production of vanillin are very desirable and thus, under current investigation. Porous coordination polymers (PCPs) are a new class of highly crystalline materials that recently have been used for catalysis. HKUST-1 (Cu3(BTC)2(H2O)3, BTC = 1,3,5-benzene-tricarboxylate) is a very well known PCP which has been extensively studied as a heterogeneous catalyst. Here, we report a synthetic strategy for the production of vanillin by the oxidation of trans-ferulic acid using HKUST-1 as a catalyst.

CO2 capture enhancement in InOF-1 via the bottleneck effect of confined ethanol.

CO2 capture of InOF-1 was enhanced 3.6-fold, at 1 bar and 30 °C, by confining EtOH within its pores. Direct visualisation by single crystal X-ray diffraction revealed that EtOH divides InOF-1 channels in wide sections separated by "bottlenecks" caused by EtOH molecules bonded to the µ2-OH functional groups of InOF-1.

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.