Adsorption characteristics of chloroform on modified zeolites from gaseous phase as well as its aqueous solution

Adsorption and Detection of Hazardous Trace Gases by Metal-Organic Frameworks

The quest for advanced designer adsorbents for air filtration and monitoring hazardous trace gases has recently been more and more driven by the need to ensure clean air in indoor, outdoor, and industrial environments. How to increase safety with regard to personal protection in the event of hazardous gas exposure is a critical question for an ever-growing population spending most of their lifetime indoors, but is also crucial for the chemical industry in order to protect future generations of employees from potential hazards. Metal-organic frameworks (MOFs) are already quite advanced and promising in terms of capacity and specific affinity to overcome limitations of current adsorbent materials for trace and toxic gas adsorption. Due to their advantageous features (e.g., high specific surface area, catalytic activity, tailorable pore sizes, structural diversity, and range of chemical and physical properties), MOFs offer a high potential as adsorbents for air filtration and monitoring of hazardous trace gases. Three advanced topics are considered here, in applying MOFs for selective adsorption: (i) toxic gas adsorption toward filtration for respiratory protection as well as indoor and cabin air, (ii) enrichment of hazardous gases using MOFs, and (iii) MOFs as sensors for toxic trace gases and explosives.

Highly selective adsorption and separation of dichloromethane/trichloromethane on a copper-based metal–organic framework

CuBTC (HKUST-1) has been proven to be a great candidate for highly selective adsorption and separation of dichloromethane and trichloromethane.

Amino-functionalized metal–organic framework for adsorption and separation of dichloromethane and trichloromethane

MOF functionalized with –NH₂ exhibits improved adsorption capacity and selectivity for the adsorption and separation of dichloromethane and trichloromethane.

Cation Mobility and the Sorption of Chloroform in Zeolite NaY: Molecular Dynamics Study

Molecular dynamics simulations at temperatures of 270, 330, and 390 K have been carried out to address the question of cation migration upon chloroform sorption in sodium zeolite Y. The results show that sodium cations located in different sites exhibit different types of mobility. These may be summarized as follows: (1) SII cations migrate toward the center of the supercage upon sorption, due to interactions with the polar sorbate molecules. (2) SI' cations hop from the sodalite cage into the supercage to fill vacant SII sites. (3) SI' cations migrate to other SI' sites within the same sodalite cage. (4) SI cations hop out of the double six-rings into SI' sites. In some instances, concerted motion of cations is observed. Furthermore, former SI' and SI cations, having crossed to SII sites, may then further migrate within the supercage, as in (1). The cation motion is dependent on the level of sorbate loading, with 10 molecules per unit cell not being enough to induce significant cation displacements, whereas the sorption of 40 molecules per unit cell results in a number of cations being displaced from their original positions. Further rearrangement of the cation positions is observed upon evacuation of the simulation cell, with some cations reverting back to sites normally occupied in bare NaY.

Direct observation of host-guest hydrogen bonding in the zeolite NaY/chloroform system by neutron scattering

The differential H pair distribution function obtained from neutron scattering contrast measurements on hydrogenous and deuterated chloroform adsorbed into zeolite NaY (two molecules per supercage) reveals direct evidence for hydrogen bonding between hydrogen atoms on the sorbate molecule and oxygen atoms of the zeolite framework. A vector between the hydrogen and framework Si/Al atoms is also observed. The results confirm the conclusions drawn from previous vibrational spectroscopy and computer modeling studies.