Promoting Catalytic Performance Involving Hydrogen Spillover by Ion Exchange of Pt@A Catalysts to Regulate Reactant Adsorption.

Zeolite-encapsulated metal nanoparticle systems have exhibited interesting catalytic performances via the hydrogen spillover process, yet how to further utilize the function of zeolite supports to promote catalytic properties in such a process is still challenging and has rarely been investigated. Herein, to address this issue, the strategy to strengthen the adsorption energy of reactant onto the zeolite surface via a simple ion exchange method has been implemented. Ion-exchanged linde type A (LTA) zeolite-encapsulated platinum nanoclusters (Pt@NaA, Pt@HA, Pt@KA, and Pt@CaA) were prepared to study the influence of ion exchange on the catalytic performance in the model reaction of hydrogenation of acetophenone to 1-phenylethanol. The reaction results showed that the Pt@CaA catalyst exhibited the best catalytic activity in the series of encapsulated catalysts, and the selectivity of 1-phenylethanol approached 100%. As revealed by density functional theory (DFT) calculations and acetophenone temperature-programmed desorption (acetophenone-TPD) experiments, in comparison with introduced cations of Na+, H+, and K+, ion-exchanged Ca2+ on the zeolite maximumly enhanced the adsorption of carbonyl groups in acetophenone, playing a critical role in achieving the highest activity and excellent catalytic selectivity among the Pt@A catalysts.

Zeolite Encapsulation of Indole as an Antibacterial with Controllable Release Property.

Effective regulation of the release behavior of bactericides to avoid both too fast release and too slow release to maximize their antibacterial ability is still the face of a grand challenge. In this study, indole as a bactericide was encapsulated into three types of zeolites (denoted as indole@zeolite), including the ZSM-22 zeolite, ZSM-12 zeolite, and beta zeolite with different topologies, respectively, to obtain indole@ZSM-22, indole@ZSM-12, and indole@Beta complexes finally. Benefiting from the confinement effect of zeolites, the release rate of indole from these three zeolite encapsulation systems showed a much slower release rate than that of indole impregnated onto a counterpart zeolite (denoted as indole/zeolite), thus avoiding the too-fast and too-slow release very well. As determined by molecular dynamics simulation combined with experimental results, attributed to the unequal diffusion coefficient in these three encapsulation systems caused by different zeolite topologies, the release rate of indole within these three complexes was different from each other, hence providing an effective way to avoid a too-slow release rate through choosing different zeolite topologies. The simulation results showed that the timescale of hopping of indoles in zeolites plays an important role in the dynamics in zeolites. Taking killing Escherichia coli as an instance, compared with indole/zeolite, the corresponding indole@zeolite sample exhibited more efficient and sustainable antibacterial activity for its controlled-release behavior.

Template-Guided Regioselective Encaging of Platinum Single Atoms into Y Zeolite: Enhanced Selectivity in Semihydrogenation and Resistance to Poisoning.

It is challenging to establish single metal atoms with a uniform coordination environment at targeted sites of a zeolite. In this study, single platinum atoms were selectively encaged in the six-membered rings of sodalite (SOD) cages within Y zeolite using a template-guiding strategy. During the in situ synthesis process, template molecules were designed to occupy supercages and thereby force coordinated platinum species into SOD cages. Subsequent control of the post-treatment conditions yielded the Y zeolite with selectively encaged single platinum atoms, denoted Pt@Y-SOD. The Pt@Y-SOD catalyst had good stability and excellent catalytic selectivity in the semihydrogenation reaction, and it exhibited interesting thiophene and carbon monoxide resistance in this transformation because interactions with these poisons are weakened by the configuration of the encaged single platinum atoms.