We studied a series of thermally activated delayed fluorescence (TADF) emitters based on phenothiazine–dibenzothiophene-S,S-dioxide (PTZ-DTO) electron donor–acceptor (D–A) dyads, using femtosecond/nan...

Transition metal silicates (hydroxides) have been extensively studied as electrode materials, particularly as electrocatalysts for the oxygen evolution reaction (OER). However, their synthesis has not...

Zeolite-like supramolecular assemblies (ZSAs) are a distinctive class of hydrogen-bonded organic frameworks (HOFs) that form zeolite-like structures using fundamental four-membered ring (4 MR) buildin...

Two different coordinated Fe3+ ions in Co─Fe bimetallic silicate hydroxide are confirmed and distinguished in effects on properties and oxygen evolution reaction (OER) performances by introducing Al ...

Ga/ZSM-5 is among the most promising catalysts for propane dehydrogenation (PDH) to selectively produce propylene, which is one of the most important feedstocks in chemical industry. PDH over Ga/ZSM-5 operates at harsh conditions (T > 800 K), limiting the in-depth and in situ characterization of the catalysts. The Ga speciation and the structures of active sites on Ga/H-ZSM-5 in dehydrogenation have remained in active discussion as they have not been solved clearly. Furthermore, Ga species stabilized by mono-Al sites would be the most abundant Ga species; the PDH pathways over them would be different from those of Ga-oxo or reduced Ga species trapped by dual-Al sites in Ga/ZSM-5, and were reported to exhibit unexpectedly high performance. To bridge these gaps, the potential catalytic roles and evolution of [Ga]+, [GaH2]+, and [Ga]3+ in the channel and on the surface of ZSM-5 in PDH were investigated with first-principles-based calculations. We showed that dynamically generated undercoordinated [GaH2]+ (Sin-[GaH2]+) would exhibit superior catalytic performance as compared with other mononuclear reduced Ga species stabilized by mono-Al sites at the operation conditions. Though [Ga]+ is thermodynamically more plausible, [GaH2]+ is also kinetically favored on PDH pathways. A catalytic cycle of PDH was proposed connecting the concerted pathway over [Ga]+ and the alkyl pathway over [GaH2]+, showing the strong coupling between the evolution of Ga species and the conversion of propane. We also proposed that, competing with PDH and the interconversion, [Ga]+ and [GaH2]+ may also evolve and transport to form [Ga]3+ in channels or on the surface of zeolites, and this transportation also changes the Ga/Al ratio, forming Ga species that are more active than [GaH2]+ and [Ga]+ in situ and may account for the observed PDH performance of Ga/ZSM-5. The findings may help to rationalize the understanding of PDH performance of Ga/ZSM-5 and benefit the design of novel catalysts with superior PDH performance.

The separation of C3H6/C2H4 mixtures is a critical process in MTO reactions, which remains a great challenge because of their similar physicochemical properties. Immobilizing functional groups in MOFs has emerged as an effective strategy for tuning pore environments and improving the C3H6/C2H4 separation performance. Herein, two isoreticular and functionalized Zn-MOFs are successfully designed and constructed to separate MTO products, namely, CH3-decorated JLU-MOF125 and NH2-decorated JLU-MOF126. The two MOFs feature moderate pore volumes, micropore structures, and rich N/O sites, which collectively contribute to exceptional C3H6/C2H4 separation efficiency. Ultrahigh polymer-grade (>99.9%) C2H4 (1146.1 and 1138.6 L/kg, respectively) can be obtained from the dynamic breakthrough experiments of JLU-MOF125 and JLU-MOF126, and 29.6 and 48.9 L/kg of C3H6 (>99.5%) can be recovered, respectively. More importantly, both MOFs exhibit remarkable stability and the breakthrough curves remain nearly unchanged after 5 cycles, which makes them promising materials for the separation of MTO products in industrial application.