Selectivity Control in the Direct CO Esterification over Pd@UiO-66: The Pd Location Matters

Interfacial Electronic Interactions Between Ultrathin NiFe-MOF Nanosheets and Ir Nanoparticles Heterojunctions Leading to Efficient Overall Water Splitting

Creating specific noble metal/metal-organic framework (MOF) heterojunction nanostructures represents an effective strategy to promote water electrolysis but remains rather challenging. Herein, a heterojunction electrocatalyst is developed by growing Ir nanoparticles on ultrathin NiFe-MOF nanosheets supported by nickel foam (NF) via a readily accessible solvothermal approach and subsequent redox strategy. Because of the electronic interactions between Ir nanoparticles and NiFe-MOF nanosheets, the optimized Ir@NiFe-MOF/NF catalyst exhibits exceptional bifunctional performance for the hydrogen evolution reaction (HER) (η10 = 15 mV, η denotes the overpotential) and oxygen evolution reaction (OER) (η10 = 213 mV) in 1.0 m KOH solution, superior to commercial and recently reported electrocatalysts. Density functional theory calculations are used to further investigate the electronic interactions between Ir nanoparticles and NiFe-MOF nanosheets, shedding light on the mechanisms behind the enhanced HER and OER performance. This work details a promising approach for the design and development of efficient electrocatalysts for overall water splitting.

Tailoring Type III Porous Ionic Liquids for Enhanced Liquid-Liquid Two-Phase Catalysis

Porous Ionic Liquids (PILs) have gained attention but facing challenges in catalysis, especially in liquid-liquid two-phase reactions due to limited catalytic sites and hydrophilicity control. This work engineered a Type III PILs (PILS-M) using zeolitic imidazolate framework-8 (ZIF-8) confined phosphomolybdic acid (HPMo) as the microporous framework and N-butyl pyridine bis(trifluoromethane sulfonyl) imide ionic liquid ([Bpy][NTf2]) as the solvent. The PILS-M not only combines the advantages of traditional ionic liquids and microporous frameworks, including excellent extraction, high dispersion of catalytically active species, remarkable stability, etc., but also can make the inner surface of ZIF-8 turned to be hydrophilic that favors the contact between aqueous hydrogen peroxide oxidant and catalytically active sites for the promotion of catalytic performance in reactive extractive desulfurization (REDS) processes of fuel oils. This study demonstrates Type III PILs' potential as catalysts for sustainable chemical processes, offering insights into versatile PILs applications in diverse fields.

Heteroatom-Doped Ag25 Nanoclusters Encapsulated in Metal-Organic Frameworks for Photocatalytic Hydrogen Production

Atomically precise metal nanoclusters (NCs) with unique optical properties and abundant catalytic sites are promising in photocatalysis. However, their light-induced instability and the difficulty of utilizing the photogenerated carriers for photocatalysis pose significant challenges. Here, MAg24 (M=Ag, Pd, Pt, and Au) NCs doped with diverse single heteroatoms have been encapsulated in a metal-organic framework (MOF), UiO-66-NH2, affording MAg24@UiO-66-NH2. Strikingly, compared with Ag25@UiO-66-NH2, the MAg24@UiO-66-NH2 doped with heteroatom exhibits much enhanced activity in photocatalytic hydrogen production, among which AuAg24@UiO-66-NH2 presents the best activity up to 3.6 mmol g-1 h-1, far superior to all other counterparts. Moreover, they display excellent photocatalytic recyclability and stability. X-ray photoelectron spectroscopy and ultrafast transient absorption spectroscopy demonstrate that MAg24 NCs encapsulated into the MOF create a favorable charge transfer pathway, similar to a Z-scheme heterojunction, when exposed to visible light. This promotes charge separation, along with optimized Ag electronic state, which are responsible for the superior activity in photocatalytic hydrogen production.

Photosynthetic System Based on a Polyoxometalate-Based Dehydrated Metal-Organic Framework for Nitrogen Fixation

In nature, biological nitrogen fixation is accomplished through the π-back-bonding mechanism of nitrogenase, which poses significant challenges for mimic artificial systems, thanks to the activation barrier associated with the N≡N bond. Consequently, this motivates us to develop efficient and reusable photocatalysts for artificial nitrogen fixation under mild conditions. We employ a charge-assisted self-assembly process toward encapsulating one polyoxometalate (POM) within a dehydrated Zr-based metal-organic framework (d-UiO-66) exhibiting nitrogen photofixation activities, thereby constructing an enzyme-mimicking photocatalyst. The dehydration of d-UiO-66 is favorable for facilitating nitrogen chemisorption and activation via the unpaired d-orbital electron at the [Zr6O6] cluster. The incorporation of POM guests enhanced the charge separation in the composites, thereby facilitating the transfer of photoexcited electrons into the π* antibonding orbital of chemisorbed N2 for efficient nitrogen fixation. Simultaneously, the catalytic efficiency of SiW9Fe3@d-UiO-66 is enhanced by 9.0 times compared to that of d-UiO-66. Moreover, SiW9Fe3@d-UiO-66 exhibits an apparent quantum efficiency (AQE) of 0.254% at 550 nm. The tactics of "working-in-tandem" achieved by POMs and d-UiO-66 are extremely vital for enhancing artificial ammonia synthesis. This study presents a paradigm for the development of an efficient artificial catalyst for nitrogen photofixation, aiming to mimic the process of biological nitrogen fixation.