Flexible Zirconium MOFs as Bromine‐Nanocontainers for Bromination Reactions under Ambient Conditions

A series of flexible MOFs (PCN‐605, PCN‐606, and PCN‐700) are synthesized and applied to reversible bromine encapsulation and release. The chemical stability of these Zr‐MOFs ensures the framework's integrity during the bromine adsorption, while the framework's flexibility allows for structural adaptation upon bromine uptake to afford stronger host–guest interactions and therefore higher bromine adsorption capacities. The flexible MOFs act as bromine‐nanocontainers which elongate the storage time of volatile halides under ambient conditions. Furthermore, the bromine pre‐adsorbed flexible MOFs can be used as generic bromine sources for bromination reactions giving improved yields and selectivities under ambient conditions when compared with liquid bromine.     

An Efficient,Visible‐Light‐Driven,Hydrogen Evolution Catalyst NiS/ZnxCd1−xS Nanocrystal Derived from a Metal–Organic Framework

Photocatalytic water splitting for hydrogen production using sustainable sunlight is a promising alternative to industrial hydrogen production. However, the scarcity of highly active, recyclable, inexpensive photocatalysts impedes the development of photocatalytic hydrogen evolution reaction (HER) schemes. Herein, a metal–organic framework (MOF)‐template strategy was developed to prepare non‐noble metal co‐catalyst/solid solution heterojunction NiS/Zn_xCd_1−xS with superior photocatalytic HER activity. By adjusting the doping metal concentration in MOFs, the chemical compositions and band gaps of the heterojunctions can be fine‐tuned, and the light absorption capacity and photocatalytic activity were further optimized. NiS/Zn_0.5Cd_0.5S exhibits an optimal HER rate of 16.78 mmol g⁻¹ h⁻¹ and high stability and recyclability under visible‐light irradiation (λ>420 nm). Detailed characterizations and in‐depth DFT calculations reveal the relationship between the heterojunction and photocatalytic activity and confirm the importance of NiS in accelerating the water dissociation kinetics, which is a crucial factor for photocatalytic HER.     

Reentrant Structural Transitions and Collapse of Charge and Orbital Orders in Quadruple Perovskites

Charge and orbital degrees of freedom determine properties of many materials, and are central to many important phenomena. At high temperatures, thermal fluctuations overcome them, and high‐symmetry structures are realized. On decreasing temperature, different charge‐ and orbital‐order transitions take place accompanied by symmetry lowering. Remarkable exceptions to this general tendency, realized in Cu‐doped BiMn₇O₁₂ quadruple perovskites, are presented. Introduction of Cu²⁺ produces mixtures of Mn³⁺ and Mn⁴⁺ and charge degree of freedom. BiCuMn₆O₁₂ (and compositions in the vicinity) exhibits well‐defined 1:3 charge order of Mn⁴⁺ and Mn³⁺ and orbital order of Mn³⁺ near room temperature, but both charge and orbital orders collapse below about 115 K with the reentrance of the high‐temperature cubic Im phase. What is interesting the collapse can be controlled by a magnetic field even without long‐range magnetic order, and the collapsed phase shows nearly zero thermal expansion.     

Sorting of C4 Olefins with Interpenetrated Hybrid Ultramicroporous Materials by Combining Molecular Recognition and Size‐Sieving

C₄ olefin separations present one of the great challenges in hydrocarbon purifications owing to their similar structures, thus a single separation mechanism often met with limited success. Herein we report a series of anion‐pillared interpenetrated copper coordination for which the cavity and functional site disposition can be varied in 0.2 Å scale increments by altering the anion pillars and organic linkers (GeFSIX‐2‐Cu‐i (ZU‐32), NbFSIX‐2‐Cu‐i (ZU‐52), GeFSIX‐14‐Cu‐i (ZU‐33)), which enable selective recognition of different C₄ olefins. In these materials the rotation of the organic linkers is controlled to create a contracted flexible pore window that enables the size‐exclusion of specific C₄ olefins, while still adsorbing significant amounts of 1,3‐butadiene (C₄H₆) or 1‐butene (n‐C₄H₈). Combining the molecular recognition and size‐sieving effect, these materials unexpectedly realized the sieving of C₄H₆/n‐C₄H₈, C₄H₆/iso‐C₄H₈, and n‐C₄H₈/iso‐C₄H₈ with high capacity.     

A Convenient and Versatile Amino‐Acid‐Boosted Biomimetic Strategy for the Nondestructive Encapsulation of Biomacromolecules within Metal–Organic Frameworks

Herein, an amino‐acid‐boosted biomimetic strategy is reported that enabled the rapid encapsulation, or co‐encapsulation, of a broad range of proteins into microporous metal–organic frameworks (MOFs), with an ultrahigh loading efficiency. It relies on the accelerated formation of prenucleation clusters around proteins via a metallothionein‐like self‐assembly. The encapsulated proteins maintained their native conformations, and the structural confinement within porous MOFs endowed enzymes with excellent bioactivity, even in harsh conditions (e.g. in the presence of proteolytic or chemical agents or at high temperature). Furthermore, owing to the merits of nondestructive and protein surface charge‐independent encapsulation, the feasibility of this biomimetic strategy for biostorage, enzyme cascades, and biosensing was also verified. It is believed that this convenient and versatile encapsulation strategy has great promise in the important fields of biomedicine, catalysis, and biosensing.     

Guest‐Switchable Multi‐Step Spin Transitions in an Amine‐Functionalized Metal–Organic Framework

Materials with hysteretic multi‐step spin‐crossover (SCO) have potential application in high‐order data storage. Here, an unprecedented hysteretic four‐step SCO behavior with the sequence of LS↔HS_0.25LS_0.75↔HS_0.5LS_0.5↔ HS_0.75LS_0.25↔HS is found in a three‐dimensional (3D) Hofmann‐type metal–organic framework (MOF), which is evidenced by magnetic, differential scanning calorimetry, and crystal data. Further experiments involving guest exchange leads to the first reversible modulation of four‐, two‐, and one‐stepped SCO behaviors, which provides a new strategy for developing multi‐step SCO materials.     

Photofunctionality in Porphyrin‐Hybridized Bis(dipyrrinato)zinc(II) Complex Micro‐ and Nanosheets

New bis(dipyrrinato)zinc(II) complex micro‐ and nanosheets containing zinc(II) porphyrin ( N2 ) are synthesized. A liquid/liquid interface method between dipyrrin porphyrin ligand L2 and zinc acetate produces N2 with a large domain size. N2 can be layered quantitatively onto a flat substrate by a modified Langmuir–Schäfer method. N2 deposited on a SnO₂ electrode functions as a photoanode for a photoelectric conversion system. The photoresponse of N2 covers the whole visible wavelength range (400–650 nm), with a maximum quantum efficiency of more than twice that of a bis(dipyrrinato)zinc(II) complex nanosheet without porphyrin.     

Boosting Electrocatalytic Hydrogen Evolution over Metal–Organic Frameworks by Plasmon‐Induced Hot‐Electron Injection

Efficient hydrogen evolution via electrocatalytic water splitting holds great promise in modern energy devices. Herein, we demonstrate that the localized surface plasmon resonance (LSPR) excitation of Au nanorods (NRs) dramatically improves the electrocatalytic hydrogen evolution activity of CoFe‐metal–organic framework nanosheets (CoFe‐MOFNs), leading to a more than 4‐fold increase of current density at ?0.236 V (vs. RHE) for Au/CoFe‐MOFNs composite under light irradiation versus in dark. Mechanistic investigations reveal that the hydrogen evolution enhancement can be largely attributed to the injection of hot electrons from AuNRs to CoFe‐MOFNs, raising the Fermi level of CoFe‐MOFNs, facilitating the reduction of H₂O and affording decreased activation energy for HER. This study highlights the superiority of plasmonic excitation on improving electrocatalytic efficiency of MOFs and provides a novel avenue towards the design of highly efficient water‐splitting systems under light irradiation.     

MOF‐5‐Polystyrene: Direct Production from Monomer,Improved Hydrolytic Stability,and Unique Guest Adsorption

An unprecedented mode of reactivity of Zn₄O‐based metal–organic frameworks (MOFs) offers a straightforward and powerful approach to polymer‐hybridized porous solids. The concept is illustrated with the production of MOF‐5‐polystyrene wherein polystyrene is grafted and uniformly distributed throughout MOF‐5 crystals after heating in pure styrene for 4–24 h. The surface area and polystyrene content of the material can be fine‐tuned by controlling the duration of heating styrene in the presence of MOF‐5. Polystyrene grafting significantly alters the physical and chemical properties of pristine MOF‐5, which is evident from the unique guest adsorption properties (solvatochromic dye uptake and improved CO₂ capacity) as well as the dramatically improved hydrolytic stability of composite. Based on the fact that MOF‐5 is the best studied member of the structure class, and has been produced at scale by industry, these findings can be directly leveraged for a range of current applications.     

Layer‐by‐Layer Assembled Conductive Metal–Organic Framework Nanofilms for Room‐Temperature Chemiresistive Sensing

The utility of electronically conductive metal–organic frameworks (EC‐MOFs) in high‐performance devices has been limited to date by a lack of high‐quality thin film. The controllable thin‐film fabrication of an EC‐MOF, Cu₃(HHTP)₂, (HHTP=2,3,6,7,10,11‐hexahydroxytriphenylene), by a spray layer‐by‐layer liquid‐phase epitaxial method is reported. The Cu₃(HHTP)₂ thin film can not only be precisely prepared with thickness increment of about 2 nm per growing cycle, but also shows a smooth surface, good crystallinity, and high orientation. The chemiresistor gas sensor based on this high‐quality thin film is one of the best room‐temperature sensors for NH₃ among all reported sensors based on various materials.     

Phosphorus‐Modulation‐Triggered Surface Disorder in Titanium Dioxide Nanocrystals Enables Exceptional Sodium‐Storage Performance

Structural modulation and surface engineering have remarkable advantages for fast and efficient charge storage. Herein, we present a phosphorus modulation strategy which simultaneously realizes surface structural disorder with interior atomic‐level P‐doping to boost the Na⁺ storage kinetics of TiO₂. It is found that the P‐modulated TiO₂ nanocrystals exhibit a favourable electronic structure, and enhanced structural stability, Na⁺ transfer kinetics, as well as surface electrochemical reactivity, resulting in a genuine zero‐strain characteristic with only approximately 0.1 % volume variation during Na⁺ insertion/extraction, and exceptional Na⁺ storage performance including an ultrahigh rate capability of 210 mAh g^?1 at 50 C and a strong long‐term cycling stability without significant capacity decay up to 5000 cycles at 30 C.