Flower-Like Molybdenum Disulfide for Polarity-Triggered Accumulation/Release of Small Molecules

Flower-like molybdenum disulfide (MoS₂) with rich edge sites has been prepared by the hydrothermal method. The edge sites possess polarity due to the noncentrosymmetric Mo-S on exposed (100) facets and thus show a strong electrostatic attraction toward polar species. The flower-like MoS₂ can be used as small-molecule carriers for the model drug, Rhodamine B (RhB). The results prove that flower-like MoS₂ have fast adsorption kinetics and perform a switchable accumulation/release with response to the solvent polarity. An outstanding reusability can be found in flower-like MoS₂ due to little cargo retention, and the recycle of adsorption can be repeated 100 times with above 88.5% of the adsorption capacity retained. The flower-like MoS₂ with solvent polarity-triggered loading/release can be extended to controlled release and color switch of display.

Smart Adsorbents with Photoregulated Molecular Gates for Both Selective Adsorption and Efficient Regeneration

Selective adsorption and efficient regeneration are two crucial issues for adsorption processes; unfortunately, only one of them instead of both is favored by traditional adsorbents with fixed pore orifices. Herein, we fabricated a new generation of smart adsorbents through grafting photoresponsive molecules, namely, 4-(3-triethoxysilylpropyl-ureido)azobenzene (AB-TPI), onto pore orifices of the support mesoporous silica. The azobenzene (AB) derivatives serve as the molecular gates of mesopores and are reversibly opened and closed upon light irradiation. Irradiation with visible light (450 nm) causes AB molecules to isomerize from cis to trans configuration, and the molecular gates are closed. It is easy for smaller adsorbates to enter while difficult for the larger ones, and the selective adsorption is consequently facilitated. Upon irradiation with UV light (365 nm), the AB molecules are transformed from trans to cis isomers, promoting the desorption of adsorbates due to the opened molecular gates. The present smart adsorbents can consequently benefit not only selective adsorption but also efficient desorption, which are exceedingly desirable for adsorptive separation but impossible for traditional adsorbents with fixed pore orifices.

Intramolecular Hydrogen Bonds Enhance Disparity in Reactivity between Isomers of Photoswitchable Sorbents and CO2 : A Computational Study

Reducing the emission of greenhouse gases, such as CO2 , requires efficient and reusable capture materials. The energy for regenerating sorbents is critical to the cost of CO2 capture. Here, we design a series of photoswitchable CO2 capture molecules by grafting Lewis bases, which can covalently bond CO2 , to azo-based backbones that can switch configurations upon light stimulation. The first-principles calculations demonstrate that intramolecular hydrogen bonds are crucial for enlarging the difference of CO2 binding strengths to the cis and trans isomers. As a result, the CO2 -sorbent interaction can be light-adjusted from strong chemical bonding in one configuration to weak bonding in the other, which may lead to a great energy reduction in sorbent regeneration.