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Although anisotropic phononic crystals (PnCs) could be utilized to control the phonon dispersions and thermal transports, rapidly discovering their properties presents a significant challenge due to the enormous consumption of traditional computational methods. In this study, we have developed machine learning techniques to forecast the thermal conductance of anisotropic PnCs (GPnC and GPnC/Gmem) based on the elastic constants, taking conventional inorganic and halide perovskites as examples for their thermoelectric applications. Our findings suggest that predicting GPnC/Gmem is more challenging than predicting GPnC attribute to the complex influence factors and spatial distribution patterns of the former. The GPnC and GPnC/Gmem of the weakest thermal anisotropic materials—all hexagonals are invariants in the (0 0 1) plane, because the velocities in this plane are direction-independent. The GPnC and GPnC/Gmem of the strongest thermal anisotropic material FAPbI3 reaches the minimum and maximum values in [1 1 0] and [1 0 0] directions, respectively. Ultimately, our machine learning models can map the hidden complex nonlinear relationships between target thermal properties and mechanical features to provide valuable insight for accurate and efficient prediction and analysis of the thermal behaviors of PnCs at a mesoscopic level under low temperatures. [ABSTRACT FROM AUTHOR]

The issue includes metal-organic frameworks, covalent-organic frameworks, hybrid organic-inorganic perovskites, and metal oxides, with different structural dimensionalities (1D, 2D, and 3D) and morphological scales (nano, micro, and bulk). Li-rich Mn-based layered oxides are outstanding candidates as cathode materials, but the decline of capacity and discharge potential, induced by the phase transformation during the charge-discharge cycling, is a challenge for their practical applications (article number 2100864). In this regard, Prof. Jang and co-workers summarize the applications of 2D metal/covalent-organic frameworks in the field of electrocatalysis (article number 2003990), Prof. Eddaoudi and co-workers outline 2D covalent-organic framework-based electrodes for supercapacitors and metal-ion batteries (article number 2100177), and Prof. Bu and co-workers summarize the metal/covalent-organic framework based cathodes for metal-ion batteries (article number 2100172). [Extracted from the article]

Recent years have witnessed the prosperous developments of crystalline materials based on diverse organic/inorganic small molecules, metal organic frameworks (MOFs), covalent organic frameworks (COFs), etc. In terms of luminescent species encapsulated host-guest MOFs, Prof. Xian-He Bu and co-workers provide a comprehensive review on the construction strategies and optical applications of luminescent particles hybridized MOFs materials (adom.202100283). Lead halide perovskites have recently emerged as highly promising optoelectronic materials owing to their low-cost solution fabrication, chemical versatility, tolerance to defects, large absorption coefficient, and high charge carrier mobility. [Extracted from the article]

Abstract: Crystallization of tetrazole compound, 2-(1H-tetrazol-5-yl)pyrazine (TZP), from water gives rise to the 2:1 hydrate, TZP·(TZP·H2O), with entangled structure involving two-dimensionally distinct strong hydrogen-bonded motifs of 1-D sawtooth chain and 3-D ths net (also called ThSi2, (10,3)-b net). In the former, TZP molecules link each other in an end-to-end mode by NN(pyrazine) hydrogen bonds (C(6) synthon), while in the latter, both TZP and water molecules assemble through ON(tetrazol), ON(pyrazine) and NO hydrogen bonds with each acting as a 3-connected node. There also exist weak hydrogen bonds of the CN(tetrazol) between such 1-D chains and the 3-D net, and between adjacent chains, respectively. This result represents a rare example of hydrogen-bonded polythreading organic structure, and further exploits the using of tetrazole compound in hydrogen-bonded crystal engineering. [Copyright &y& Elsevier]

A pentacoordinate monomeric CuII complex, [Cu(H2O)(HL1)(L2)](NO3)(H2O) (1), with the mixed ligands (where H2L1=pyridine-2,6-dicarboxylic acid and L2=3-(2-pyridyl)pyrazole), has been synthesized and characterized by elemental analyses, IR, thermogravimetric analysis and X-ray diffraction techniques. X-ray structural analysis of complex 1 revealed that the CuII center has a CuN3O2 distorted square pyramid environment with three N atoms of two different ligands and an O atom of coordinated water molecule constituting the mean plane, and one O atom of ligand HL1 occupying the axial site. The H2L1 ligand is mono-deprotonated in this structure, and only one oxygen atom of the carboxylate group coordinates to the CuII center. A striking structural feature of complex 1 is the three-dimensional supramolecular architecture formed through intermolecular C–H⋯O, O–H⋯O and N–H⋯O hydrogen-bonding interactions. The IR and ESR spectra, and thermogravimetric analysis of complex 1 have been further investigated. [Copyright &y& Elsevier]

The mononuclear CuII complex [CuL(H2O)]·2H2O (1) with a diazamesocyclic ligand bearing two functional carboxylic donor groups, 1,5-diazacyclooctane-N,N′-diacetate acid (H2L), has been synthesized and characterized by elemental analyses, thermal analyses and IR spectrum. The crystal structure of 1 has been determined by X-ray diffraction analysis, which revealed that the CuII center coordinates to the tetradentate chelated ligand L and an axial water molecule, and the 1,5-diazacyclooctane (DACO) moiety adopts a boat/chair conformation that inhibits the axial coordination at the metal center to form this penta-coordinated pyramidal (CuN2O3) complex. The most striking feature of this structure is the formation of a novel two-dimensional joint-ladder like architecture through multiple inter- and intramolecular O–H⋯O hydrogen bonds. The solution behaviors of 1 have been further investigated by conductance, UV–Vis and ESR techniques. [Copyright &y& Elsevier]

The complexes of Cu(I), Cu(II), Ni(II), Zn(II) and Co(II) with a new polypyridyl ligand, 2,3-bis(2-pyridyl)-5,8-dimethoxyquinoxaline (L), have been synthesized and characterized. The crystal structures of these complexes have been elucidated by X-ray diffraction analyses and three types of coordination modes for L were found to exist in them. In the dinuclear complex [Cu(I)L(CH3CN)]2·(ClO4)2 (1), L acts as a tridentate ligand with two Cu(I) centers bridged by two L ligands to form a box-like dimeric structure, in which each Cu(I) ion is penta-coordinated with three nitrogen atoms and a methoxyl oxygen atom of two L ligands, and an acetonitrile. In [Cu(II)L(NO3)2]·CH3CN 2, the Cu(II) center is coordinated to the two nitrogen atoms of the two pyridine rings of L which acts as a bidentate ligand. The structures of [Ni(II)L(NO3)(H2O)2]·2CH3CN·NO3 (3), [Zn(II)L(NO3)2 (H2O)]·2CH3CN (4) and [Co(II)LCl2(H2O)] (5) are similar to each other in which L acts as a tridentate ligand by using its half side, and the metal centers are coordinated to a methoxyl oxygen atom and two bipyridine nitrogen atoms of L in the same side. The formation of infinite quasi-one-dimensional chains (1, 4 and 5) or a quasi-two-dimensional sheet (2) assisted by the intra- or intermolecular face-to-face aryl stacking interactions and hydrogen bonds may have stabilized the crystals of these complexes. Luminescence studies showed that 1 exhibits broad, structureless emissions at 420 nm in the solid state and at 450 nm in frozen alcohol frozen glasses at 77 K. Cyclic voltammetric studies of 1 show the presence of an irreversible metal-centered reduction wave at approximately −0.973 V versus Fc+/0 and a quasi-reversible ligand-centered reduction couple at approximately −1.996 V versus Fc+/0. The solution behaviors of these complexes have been further studied by UV–Vis and ESR techniques. [Copyright &y& Elsevier]

With the aim of examining the metal-assisted rearrangement behaviors of 2,2′-pyridil (L), its reactions with M(ClO4)2·6H2O (M=CoII, NiII and CuII) were considered. X-ray diffraction analyses of the products reveal the formation of complexes containing 2,2′-pyridilate anion (L1) or picolinate anion (L2) as arrangement products of 2,2′-pyridil, induced by different metal ions. [CoIII(L1)2](ClO4)·CH3OH (1) and [NiII(L1)2]·2H2O (2) have similar mononuclear structures, and it should be noted that the CoII ion is unstable to oxidation in this process. However, [CuII(L2)2]·2H2O (3) forms a one-dimensional linear complex via Cu–O weak interactions. [Copyright &y& Elsevier]

Fluoropolymers and metal halide perovskites (MHPs), as two classes of important piezoelectric materials, suffer from active phases through a facile process and brittleness led poor manufacturability, respectively. Here, TMCM‐CdCl3/PVDF nanocomposites (TMCM = trimethylchloromethyl ammonium, PVDF = polyvinylidene fluoride) are synthesized to overcome the above shortcomings. The abundant hydrogen (H) and chlorine (Cl) sites in TMCM‐CdCl3 can interlock with H and fluorine (F) atoms within PVDF via C─H···Cl and C─H···F interactions. This programming effect augments the dipole alignment and consequently promotes the formation of polar phases within PVDF. The devices made by these nanocomposites exhibit high energy harvesting properties surpassing established MHP/PVDF analogues, and prominent performance in sensing delicate human motions. Moreover, the devices show exceptional capabilities for detecting underwater ultrasound waves. The signal intensity is ≈4 times that of commercial PVDF film devices, and the frequency distortion is only a quarter of that observed in commercial ceramic transducers. This study opens up new possibilities for developing high‐performance piezoelectric nanocomposites and the creation of advanced electromechanical devices. [ABSTRACT FROM AUTHOR]

Organic piezochromic materials that manifest pressure‐stimuli‐responses are important in various fields such as data storage and anticounterfeiting. The manipulation of piezofluorochromic behaviors for these materials is promising but remains a great challenge. Herein, a non‐luminous components regulated strategy is developed and organic molecular cages (OMCs), a burgeoning class of crystalline organic materials with structural dynamics, are first explored for the design of piezofluorochromic materials with tunable luminescence. A series of OMCs based on aggregation‐induced emission (AIE) chromophores, termed Cage 1–3, are synthesized and their piezofluorochromic behaviors are investigated by diamond anvil cell technique. Due to the sufficient voids between its flexible chromophores offered by the OMC structure, Cage 1 exhibits thermofluorochromic and piezofluorochromic properties. Moreover, the piezofluorochromic performance of this OMC could be further promoted by replacing its non‐luminous components with improved flexibilities, and a remarkable luminescence peak shift by 150 nm together with a response sensitivity of 13.8 nm GPa−1 was achieved upon hydrostatic compression. The cage structure plays a vital role in facilitating efficient and reversible piezofluorochromic behaviors. This study has shed light on the rational design and exploitation of OMCs as an exceptional platform to accomplish customizable piezofluorochromic behaviors and enlarge their potential applications in pressure‐based luminescence. [ABSTRACT FROM AUTHOR]

Organic piezochromic materials that manifest pressure‐stimuli‐responses are important in various fields such as data storage and anticounterfeiting. The manipulation of piezofluorochromic behaviors for these materials is promising but remains a great challenge. Herein, a non‐luminous components regulated strategy is developed and organic molecular cages (OMCs), a burgeoning class of crystalline organic materials with structural dynamics, are first explored for the design of piezofluorochromic materials with tunable luminescence. A series of OMCs based on aggregation‐induced emission (AIE) chromophores, termed Cage 1–3, are synthesized and their piezofluorochromic behaviors are investigated by diamond anvil cell technique. Due to the sufficient voids between its flexible chromophores offered by the OMC structure, Cage 1 exhibits thermofluorochromic and piezofluorochromic properties. Moreover, the piezofluorochromic performance of this OMC could be further promoted by replacing its non‐luminous components with improved flexibilities, and a remarkable luminescence peak shift by 150 nm together with a response sensitivity of 13.8 nm GPa−1 was achieved upon hydrostatic compression. The cage structure plays a vital role in facilitating efficient and reversible piezofluorochromic behaviors. This study has shed light on the rational design and exploitation of OMCs as an exceptional platform to accomplish customizable piezofluorochromic behaviors and enlarge their potential applications in pressure‐based luminescence. [ABSTRACT FROM AUTHOR]

Pressure‐induced emission enhancement (PIEE) is a novel phenomenon in contrast to conventional pressure‐induced emission quenching, and has attracted considerable attention owing to the potential application of materials with this effect as optical pressure‐sensing devices. The urgent need and significant significance lie in the design and exploration of systems that possess high‐efficiency PIEE. Here, a large PIEE in a novel zero‐dimensional (0D) hybrid manganese bromide is realized, (BPPH)2MnBr4·1.5CH3CN [BPPH+ = bis(triphenylphosphine)iminium]. The experimental and theoretical results demonstrate that such emission enhancement is primarily attributed to the pressure‐induced reconfiguration of electronic band alignment and resultant redistribution of band‐edge excitons. Under compression, the electronic bandgap of (MnBr4)2− experiences a more rapid reduction compared to that of the organic cations. Consequently, this leads to the gradual closure of the charge transfer pathway from (MnBr4)2− to BPPH+. This progression results in a higher retention of excitons on (MnBr4)2−, amplifying the efficiency of Mn2+d–d transitions, and leading to a substantial enhancement in emission. This study not only offers fresh insights into the behavior of carrier dynamics induced by pressure in hybrid manganese halides but also presents a promising avenue for the advancement of PIEE systems. [ABSTRACT FROM AUTHOR]

Based on the electron‐withdrawing effect of the Pt(bpy)Cl2 molecule, a simple post‐modification amide reaction was firstly used to graft it onto the surface of NH2‐MIL‐125, which performed as a highly efficient electron acceptor that induced the conversion of the photoinduced charge migration pathway from internal BDC→TiOx migration to external BDC→PtNx migration, significantly improving the efficiency of photoinduced electron transfer and separation. Furthermore, precisely regulating over the first coordination sphere of Pt single atoms was achieved using further post‐modification with additional bipyridine to investigate the effect of Pt−Nx coordination numbers on reaction activity. The as‐synthesized NML‐PtN2 exhibited superior photocatalytic hydrogen evolution activity of 7.608 mmol g−1 h−1, a remarkable improvement of 225 and 2.26 times compared to pristine NH2‐MIL‐125 and NML‐PtN4, respectively. In addition, the superior apparent quantum yield of 4.01 % (390 nm) and turnover frequency of 190.3 h−1 (0.78 wt % Pt SA; 129 times compared to Pt nanoparticles/NML) revealed the high solar utilization efficiency and hydrogen evolution activity of the material. And macroscopic color changes caused by the transition of carrier migration paths was first observed. It holds profound significance for the design of MOF‐Molecule catalysts with efficient charge carrier separation and precise regulation of single‐atom coordination sphere. [ABSTRACT FROM AUTHOR]

Chiral hybrid organic–inorganic metal halides (HOMHs) offer an ideal platform for the advancement of second‐order nonlinear optical (NLO) materials owing to their inherent noncentrosymmetric structures. The enhancement of optical nonlinearity of chiral HOMHs could be achieved by matching the free exciton and/or self‐trapped exciton energy levels with desired NLO frequencies. However, the current scarcity of resonance modes and low resonance ratio hamper the further improvements of NLO performance. Herein, we propose a new resonant channel of charge transfer (CT) excited states from metal halide polyhedra to organic ligand to boost the second‐order optical nonlinearity of chiral HOMHs. The model lead halide (C7H10N)PbBr3 (C7H10N=1‐ethylpyridinium) exhibits a drastically enhanced second harmonic generation in resonance to the deep CT exciton energy, with intensity of up to 111.0 times that of KDP and 10.9 times that of urea. The effective NLO coefficient has been determined to be as high as ~40.2 pm V−1, balanced with a large polarization ratio and high laser damage threshold. This work highlights the contribution of organic ligands in the construction of a resonant channel for enhancing second‐order NLO coefficients of metal halides, and thus provides guidelines for designing new chiral HOMHs materials for advanced nonlinear photonic applications. [ABSTRACT FROM AUTHOR]

Chiral hybrid organic–inorganic metal halides (HOMHs) offer an ideal platform for the advancement of second‐order nonlinear optical (NLO) materials owing to their inherent noncentrosymmetric structures. The enhancement of optical nonlinearity of chiral HOMHs could be achieved by matching the free exciton and/or self‐trapped exciton energy levels with desired NLO frequencies. However, the current scarcity of resonance modes and low resonance ratio hamper the further improvements of NLO performance. Herein, we propose a new resonant channel of charge transfer (CT) excited states from metal halide polyhedra to organic ligand to boost the second‐order optical nonlinearity of chiral HOMHs. The model lead halide (C7H10N)PbBr3 (C7H10N=1‐ethylpyridinium) exhibits a drastically enhanced second harmonic generation in resonance to the deep CT exciton energy, with intensity of up to 111.0 times that of KDP and 10.9 times that of urea. The effective NLO coefficient has been determined to be as high as ~40.2 pm V−1, balanced with a large polarization ratio and high laser damage threshold. This work highlights the contribution of organic ligands in the construction of a resonant channel for enhancing second‐order NLO coefficients of metal halides, and thus provides guidelines for designing new chiral HOMHs materials for advanced nonlinear photonic applications. [ABSTRACT FROM AUTHOR]

Water pollutions have caused serious threats to the aquatic environment and human health, it is of great significance to monitor and control their contents in water. Compared with the traditional single treatment method, multiple treatment can simultaneously realize detection and removal of water pollutions on one material, which brings convenience and promotes comprehensive treatment for water remediation. Metal–organic frameworks (MOFs) are versatile porous materials that hold huge potential in wastewater treatments. This feature article reviews the recent advances in MOFs for multifunctional water treatment. First, strategies to design the sensing, removal and degradation functions onto MOFs are introduced. Then, the sensing, removal and degradation effects on various inorganic and organic water pollutions based on multifunctional MOF materials are summarized, and the interaction mechanisms are discussed in detail. Finally, the current challenges and the future research trends on MOF materials for wastewater treatment are discussed as well. [ABSTRACT FROM AUTHOR]

Chiral hybrid perovskites have shown great potential for applications in next‐generation optoelectronic devices. The intrinsic asymmetric structures of these chiral hybrid perovskites make them particularly promising for second‐order nonlinear optics (NLO). However, it remains still a challenge to obtain ideal perovskite NLO crystals featuring simultaneously large NLO coefficient, good optical transparency, high laser damage threshold, and stable physical and chemical properties, which are highly desirable for practical applications. Herein, a series is constructed of 1D chiral lead halide hybrid perovskites (R/S‐2‐MPD)PbX3 (2‐MPD = 2‐methylpiperidine; X = Cl, Br, I) featuring non‐centrosymmetric architectures. Among them, the (R/S‐2‐MPD)PbBr3 perovskites demonstrate superior performances in second‐order optical nonlinearity, including a large second‐harmonic generation coefficient (≈29.9 pm V–1), wide transparency region (λUV ≈ 310 nm), high laser damage threshold (≈2.84 mJ cm–2), high polarization ratio (up to 96%), and robust physical and chemical stabilities. Such a balanced performance of the chiral lead halide perovskites promises their advanced application in next‐generation photonics devices. [ABSTRACT FROM AUTHOR]

Broadband emission in hybrid lead halide perovskites (LHPs) has gained significant attention due to its potential applications in optoelectronic devices. The origin of this broadband emission is primarily attributed to the interactions between electrons and phonons. Most investigations have focused on the impact of structural characteristics of LHPs on broadband emission, while neglecting the role of electronic mobility. In this work, the study investigates the electronic origins of broadband emission in a family of 2D LHPs. Through spectroscopic experiments and density functional theory calculations, the study unveils that the electronic states of the organic ligands with conjugate effect in LHPs can extend to the band edges. These band‐edge carriers are no longer localized only within the inorganic layers, leading to electronic coupling with molecular states in the barrier and giving rise to additional interactions with phonon modes, thereby resulting in broadband emission. The high‐pressure photoluminescence measurements and theoretical calculations reveal that hydrostatic pressure can induce the reconfiguration of band‐edge states of charge carriers, leading to different types of band alignment and achieving macroscopic control of carrier dynamics. The findings can provide valuable guidance for targeted synthesis of LHPs with broadband emission and corresponding design of state‐of‐the‐art optoelectronic devices. [ABSTRACT FROM AUTHOR]

Chiral hybrid metal halides have emerged as a promising class of piezoelectric materials owing to their ease of synthesis, low acoustic impedance, and solution processibility. However, many known chiral halides crystalize in structures with only shear piezoelectricity which is less facile to be utilized compared with the longitudinal piezoelectricity, largely preventing their practical utility. In addressing this problem, chiral lead‐free S‐MPBiCl5 and R‐MPBiCl5 (MP = 2‐methylpiperazinium) with shear piezoelectricity are synthesized and the thin films orientating along the polarization direction are fabricated. These orientated films, characterized by numerous grains and compact grain boundaries, can effectively facilitate the grain boundary sliding to convert normal stress into shear stress, thus facilely activating the shear piezoelectricity. The resulting devices can accurately identify the position and type of ultrasound sources without the need for a complex acoustic impedance matching layer. Moreover, these devices can successfully sense delicate variations in momentum caused by table tennis balls. The findings open up a new pathway to utilize shear piezoelectricity that is normally considered unuseful of metal halides and other molecular piezoelectrics. [ABSTRACT FROM AUTHOR]

2D conductive metal–organic frameworks (2D c‐MOFs) have attracted increasing attention as promising electrode materials for rechargeable batteries due to their designable periodic motifs, large specific surface areas, and prominent electrical conductivity. However, the development of 2D c‐MOF electrode materials with functionality remains a significant challenge because of the limited electroactive ligand motifs available. Herein, a hexahydroxy‐substituted triazacoronene ligand (6OH‐TAC) is deliberately designed and synthesized, which coordinates with Cu2+ ions to form an unprecedented 2D c‐MOF (Cu‐TAC) with functionality sites of efficient lithium storage. The synergistic effect of TAC and CuO4 enables Cu‐TAC as an anode for lithium‐ion batteries with a superior reversible capacity of 772.4 mAh g−1 at 300 mA g−1, remarkable rate performance, and outstanding long‐term cyclability (83% capacity retention at 300 mA g−1 for 600 cycles). These metrics outperform almost all 2D c‐MOF‐based electrodes, shedding light on new opportunities for energy storage devices. [ABSTRACT FROM AUTHOR]

Purifying olefin from ternary paraffin/olefin/alkyne mixtures through a one‐step adsorption process is extremely desirable. Herein, a stable zirconium(IV) metal‐organic framework with a customized pore surface composed of nonpolar phenyl and slightly polar thiophene rings is reported to access the adsorption preference of paraffin and alkyne over olefin. Noteworthily, this material displays a superior ability to discriminate C3 hydrocarbon molecules, which is principally more challenging compared with C2 ones and rarely documented. Computational studies disclose that its featured pore shape fits well with C3 gas molecules, enabling them to get close contact with the immobilized affinity sites. Leveraging surface chemistry and pore shape engineering synergistically gives rise to excellent C3 adsorption capacities (>5 mmol g−1) and concurrently high C3H8/C3H6 (1.4) and C3H4/C3H6 (1.9) selectivities (at 298 K and 1 atm). Dynamic column breakthrough experiments demonstrate that one‐step purification of C2H4 and C3H6 can be simultaneously realized on this material. [ABSTRACT FROM AUTHOR]

To address the ever‐increasing societal demand for clean energy, electrocatalytic water splitting has attracted considerable interest for the efficient production of H2 and O2. However, the oxygen evolution reaction (OER) is inherently sluggish and poses a significant challenge to the overall water splitting process. As a result, extensive research efforts have been dedicated to pursuing various approaches in developing efficient electrocatalysts for water oxidation. The oxygen‐evolving center (OEC) of Photosystem II (PS II) is a natural model giving the prominent reference. Hence, this review discusses recent advances in the design of artificial electrocatalyst inspired by PS II. The discussion begins with a brief introduction to the fundamentals of electrocatalytic water oxidation and PS II. Subsequently, the progress of the novel electrocatalysts inspired by PS II is presented in the following two aspects: engineering various transition metal clusters to mimic the inorganic metal cluster of OEC (Mn4O5Ca), and utilizing different ligands to simulate the protein and amino acid environment around [Mn4O5Ca]. In addition to outlying the structures, catalytic activities, and corresponding mechanisms of these prepared catalysts, this present review concludes by proposing several effective development perspectives to this emerging field that warrant further investigation. [ABSTRACT FROM AUTHOR]

Hybrid organic−inorganic metal halides (HOMHs) have emerged as an ideal platform for the construction of semiconductor materials with promising optoelectronic properties. A number of HOMHs based on different metals including Sb3+ have been demonstrated with second‐harmonic generation (SHG) properties, but their nonlinear optical (NLO) performances including effective conversion wavelength range, optical stability, and NLO coefficients are not yet satisfactory. Here, by adopting a molecular design involving fluorine‐substitution on the achiral organic ammonium, this work has synthesized single crystals of two new chiral noncentrosymmetric HOMHs, (2‐FPEA)2SbX5 (X = Cl and Br), with large polarization ratios and outstanding optical transparency. The second‐order NLO coefficients of (2‐FPEA)2SbCl5 and (2‐FPEA)2SbBr5 are determined to be ≈24.3 and 21.6 pm V−1. Significantly, the Sb3+‐based HOMHs enable very high thermal stability and laser resistance. The distinguished laser‐induced damage thresholds (LDTs) have been estimated to be as high as 3.44 mJ cm−2 for (2‐FPEA)2SbCl5 and 3.32 mJ cm−2 for (2‐FPEA)2SbBr5, higher than that of the reported HOMHs. Such a highly efficient SHG performance and stability indicate the promising future of these Sb3+‐based metal halides for nonlinear photonic applications. [ABSTRACT FROM AUTHOR]

Chiral hybrid metal halides have been widely studied in the field of photondetectors, chiral optics, and spintronics due to their great structural flexibility and suitable bandgaps. Inspired by such great progress made in the abovementioned fields, continuous efforts need to be paid to seek other interesting applications for chiral hybrid metal halides. Herein, the synthesis of a pair of one‐dimensional enantiomorphic hybrid metal halide piezoelectrics, R/SMPCdCl4(R/SMP = R/S‐2‐methylpiperazine), and their applications in piezoelectric energy harvesting and sensing are reported. Density functional theory calculations show that these chiral piezoeletrics possess low elastic properties and high piezoelectric constants (16.71, 8.39, and 7.35 pC N−1). In addition, devices made of RMPCdCl4/PDMS (PDMS = polydimethylsiloxane) composite films are fabricated for piezoelectric energy harvesting and sensing. The piezoelectric energy harvesters with optimized content of 15 wt% RMPCdCl4/PDMS show not only excellent performance with an open‐circuit voltage of 2.57 V, short‐circuit current of 0.37 μA, and power density of 0.55 μW cm−2 but also outstanding stability of more than 3500 cycles. Meanwhile, these piezoelectric energy harvesters exhibit prominent sensing properties for detecting tapping, finger bending, walking, and running. It is demonstrated that chiral hybrid metal halides hold great potential in intelligent wearable and sensing devices. [ABSTRACT FROM AUTHOR]

A highly stable thiazole functionalized covalent triazine framework, namely CTF-BT-500, was developed for C2H6/C2H4 separation, which exhibits a record-high ethane uptake (99.7 cm3 g−1) among all reported COFs at 298 K and 1 bar. This work not only presents an excellent C2H6-selective adsorbent, but also provides guidance for the construction of robust adsorbents for value-added gas purification. [ABSTRACT FROM AUTHOR]

Highly adjustable photonic modules were constructed based on the heterostructures crystals of a new series of donor‐acceptor metal–organic framework (D‐A MOF) featuring highly tunable thermally activated delayed fluorescence (TADF). By introducing N‐phenylcarbazole and derivatives as donor guests into the acceptor host NKU‐111, highly tunable through‐space charge transfer based TADF could be achieved through the engineering of heavy atom effect, which result in modulatable emission wavelength (540 to 600 nm) and enhanced quantum yield (up to 30.86 %). Furthermore, by rationally integrating the D‐A MOFs with distinctive emissions, rod‐like heterostructures crystals featuring excitation position dependent tip emissions in wide wavelength range (495 to 598 nm) could be fabricated, which could serve as highly potential photonic modules for photonic circuit applications. [ABSTRACT FROM AUTHOR]

Highly adjustable photonic modules were constructed based on the heterostructures crystals of a new series of donor‐acceptor metal–organic framework (D‐A MOF) featuring highly tunable thermally activated delayed fluorescence (TADF). By introducing N‐phenylcarbazole and derivatives as donor guests into the acceptor host NKU‐111, highly tunable through‐space charge transfer based TADF could be achieved through the engineering of heavy atom effect, which result in modulatable emission wavelength (540 to 600 nm) and enhanced quantum yield (up to 30.86 %). Furthermore, by rationally integrating the D‐A MOFs with distinctive emissions, rod‐like heterostructures crystals featuring excitation position dependent tip emissions in wide wavelength range (495 to 598 nm) could be fabricated, which could serve as highly potential photonic modules for photonic circuit applications. [ABSTRACT FROM AUTHOR]

Highlights • The meaning and significance of the removal of pollutants from wastewater are illustrated. • Representative studies about MOFs for the removal of contaminants from wastewater are illustrated. • Perspectives and challenges about the removal of pollutions from wastewater by MOFs are presented. Abstract Water pollution is one of the most serious worldwide problems that endangers the survival and development of human society. Therefore, the effective and efficient removal of contaminants from water has become a hot topic. As a fast-growing branch of coordination chemistry, metal–organic frameworks (MOFs) with tailorable porous structures and numerous active sites have proved to be ideal adsorbents or photocatalysts for water purification. In this review, recent advances in the removal and degradation of water pollutants by MOFs are highlighted. In addition, the challenges and prospects in this active field are also briefly discussed. [ABSTRACT FROM AUTHOR]

Abstract: A sulfonated hollow covalent organic polymer (sh‐COP‐P) was prepared by post sulfonation of hollow covalent organic polymer (h‐COP‐P) synthesized through poly‐condensation of tetrabiphenylporphyrin (TBPP). In comparison with h‐COP‐P, sh‐COP‐P exhibits significantly enhanced adsorption capacity of organic cationic dyes in aqueous solutions accompanied with notably reduced adsorption capacity of anionic dyes. This gives sh‐COP‐P a satisfactory performance in selectively separating cationic organic dyes from anionic ones, mainly attributed to the electrostatic interaction between polymer backbone and the guest molecules. [ABSTRACT FROM AUTHOR]

The exploitation of photo-responsive metal–organic frameworks (MOFs) is important in the field of optical switching, advanced detection, and molecular machines. However, it remains challenging due to the heavy dependence on conventional organic photochromic molecules. Herein, a novel photochromic MOF based on benzophenone units, [Zn4(μ2-O)(μ3-O)(cdip)2(DMF)]n (H4cdip = 5,5′-carbonyldiisophthalic acid) (1), has been successfully synthesized. Compound 1 exhibits instant and reversible photochromic behavior under 365 nm UV and X-ray irradiation through the radical formation of benzophenone units. Furthermore, the fluorescence of 1 can be reversibly modulated during the photochromic process. The excellent stability and reproducibility make it suitable for inkless erasable printing paper. [ABSTRACT FROM AUTHOR]

Organic redox‐active materials are promising electrode candidates for lithium‐ion batteries by virtue of their designable structure and cost‐effectiveness. However, their poor electrical conductivity and high solubility in organic electrolytes limit the device's performance and practical applications. Herein, the π‐conjugated nitrogen‐containing heteroaromatic molecule hexaazatriphenylene (HATN) is strategically embedded with redox‐active centers in the skeleton of a Cu‐based 2D conductive metal–organic framework (2D c‐MOF) to optimize the lithium (Li) storage performance of organic electrodes, which delivers improved specific capacity (763 mAh g−1 at 300 mA g−1), long‐term cycling stability (≈90% capacity retention after 600 cycles at 300 mA g−1), and excellent rate performance. The correlation of experimental and computational results confirms that this high Li storage performance derives from the maximum number of active sites (CN sites in the HATN unit and CO sites in the CuO4 unit), favorable electrical conductivity, and efficient mass transfer channels. This strategy of integrating multiple redox‐active moieties into the 2D c‐MOF opens up a new avenue for the design of high‐performance electrode materials. [ABSTRACT FROM AUTHOR]

The mismatched fast‐electron‐slow‐proton process in the electrocatalytic oxygen evolution reaction (OER) severely restricts the catalytic efficiency. To overcome these issues, accelerating the proton transfer and elucidating the kinetic mechanism are highly sought after. Herein, inspired by photosystem II, we develop a family of OER electrocatalysts with FeO6/NiO6 units and carboxylate anions (TA2−) in the first and second coordination sphere, respectively. Benefiting from the synergistic effect of the metal units and TA2−, the optimized catalyst delivers superior activity with a low overpotential of 270 mV at 200 mA cm−2 and excellent cycling stability over 300 h. A proton‐transfer‐promotion mechanism is proposed by in situ Raman, catalytic tests, and theoretical calculations. The TA2− (proton acceptor) can mediate proton transfer pathways by preferentially accepting protons, which optimizes the O−H adsorption/activation process and reduces the kinetic barrier for O−O bond formation. [ABSTRACT FROM AUTHOR]

The mismatched fast‐electron‐slow‐proton process in the electrocatalytic oxygen evolution reaction (OER) severely restricts the catalytic efficiency. To overcome these issues, accelerating the proton transfer and elucidating the kinetic mechanism are highly sought after. Herein, inspired by photosystem II, we develop a family of OER electrocatalysts with FeO6/NiO6 units and carboxylate anions (TA2−) in the first and second coordination sphere, respectively. Benefiting from the synergistic effect of the metal units and TA2−, the optimized catalyst delivers superior activity with a low overpotential of 270 mV at 200 mA cm−2 and excellent cycling stability over 300 h. A proton‐transfer‐promotion mechanism is proposed by in situ Raman, catalytic tests, and theoretical calculations. The TA2− (proton acceptor) can mediate proton transfer pathways by preferentially accepting protons, which optimizes the O−H adsorption/activation process and reduces the kinetic barrier for O−O bond formation. [ABSTRACT FROM AUTHOR]

Chiral hybrid organic−inorganic perovskites (HOIPs) with intrinsic noncentrosymmetry have shown great potentials for chiroptoelectronic applications including second‐order nonlinear optics (NLO). Ideal NLO materials should simultaneously feature a large NLO coefficient, wide optical transparency, high laser damage threshold, and physicochemical stability. However, the development of applicable second‐order NLO materials has been largely restricted due to their strict requirement on structural noncentrosymmetry. Here, chiral amino acids abundant in nature have been adopted to synthesize hybrid lead halide perovskites (D‐/L‐Pro)PbI3·H2O (Pro = Proline) with resonance enhanced second‐harmonic generation (SHG). Their crystals feature balanced NLO performances with a large NLO coefficient, wide transparent region, high laser damage threshold, and high polarization ratio. This work demonstrates the promise of naturally abundant amino acids for the construction of hybrid chiral metal halide perovskites for next generation optoelectronic materials. [ABSTRACT FROM AUTHOR]

The chemical diversity and structural flexibility of lead halide perovskites (LHPs) offer tremendous opportunities to tune their optical properties through internal molecular engineering and external stimuli. Herein, we report the wide‐range and ultrapure photoluminescence emissions in a family of homologous 2D LHPs, [MeOPEA]2PbBr4−4xI4x (MeOPEA=4‐methoxyphenethylammonium; x=0, 0.2, 0.425, 0.575, 1) enabled through internal chemical pressure and external hydrostatic pressure. The chemical pressure, induced by the C−H⋅⋅⋅π interactions and halogen doping/substitution strengthens the structural rigidity to give sustained narrow emissions, and regulates the emission energy, respectively. Further manipulation of physical pressure leads to wide‐range emission tuning from 412 to 647 nm in a continuous and reversible manner. This work could open up new pathways for developing 2D LHP emitters with ultra‐wide color gamut and high color purity which are highly useful for pressure sensing. [ABSTRACT FROM AUTHOR]

The chemical diversity and structural flexibility of lead halide perovskites (LHPs) offer tremendous opportunities to tune their optical properties through internal molecular engineering and external stimuli. Herein, we report the wide‐range and ultrapure photoluminescence emissions in a family of homologous 2D LHPs, [MeOPEA]2PbBr4−4xI4x (MeOPEA=4‐methoxyphenethylammonium; x=0, 0.2, 0.425, 0.575, 1) enabled through internal chemical pressure and external hydrostatic pressure. The chemical pressure, induced by the C−H⋅⋅⋅π interactions and halogen doping/substitution strengthens the structural rigidity to give sustained narrow emissions, and regulates the emission energy, respectively. Further manipulation of physical pressure leads to wide‐range emission tuning from 412 to 647 nm in a continuous and reversible manner. This work could open up new pathways for developing 2D LHP emitters with ultra‐wide color gamut and high color purity which are highly useful for pressure sensing. [ABSTRACT FROM AUTHOR]

Lanthanide metal–organic frameworks (Ln‐MOFs) are promising for luminescence detection of volatile organic compound (VOC) vapors, but usually suffer from the silent or quenched Ln3+ emission. Herein, we report a new dual‐emissive Eu‐MOF composed of the coordinatively unsaturated Eu9 clusters that afford abundant open metal sites to form a confined "binding pocket" to facilitate the preconcentration and recognition of VOCs. Single‐crystal structural analyses reveal that specific analytes can replace the OH oscillators in the first coordination sphere of Eu3+ and form a unique hydrogen‐bonding second‐sphere adduct tying adjacent Eu9 clusters together to minimize their nonradiative vibrational decay. With the promoted Eu3+ luminescence, the MOF realizes real‐time in situ visual sensing of THF vapor (<1 s) and shows a quantitative ratiometric response to the vapor pressure with a limit of detection down to 17.33 Pa. Also, it represents a top‐performing ratiometric luminescent thermometer. [ABSTRACT FROM AUTHOR]

Lanthanide metal–organic frameworks (Ln‐MOFs) are promising for luminescence detection of volatile organic compound (VOC) vapors, but usually suffer from the silent or quenched Ln3+ emission. Herein, we report a new dual‐emissive Eu‐MOF composed of the coordinatively unsaturated Eu9 clusters that afford abundant open metal sites to form a confined "binding pocket" to facilitate the preconcentration and recognition of VOCs. Single‐crystal structural analyses reveal that specific analytes can replace the OH oscillators in the first coordination sphere of Eu3+ and form a unique hydrogen‐bonding second‐sphere adduct tying adjacent Eu9 clusters together to minimize their nonradiative vibrational decay. With the promoted Eu3+ luminescence, the MOF realizes real‐time in situ visual sensing of THF vapor (<1 s) and shows a quantitative ratiometric response to the vapor pressure with a limit of detection down to 17.33 Pa. Also, it represents a top‐performing ratiometric luminescent thermometer. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Ammonia (NH3) is one of the most important industrial feedstocks in the fields of fertilizers, drugs, explosives, ordnance, commercial cleanings, and so on. However, the features of ammonia such as high toxicity and corrosivity, and difficulty in handling would inevitably increase the risk of environmental damage and the deterioration of natural/public lands. Although sorts of solid adsorbents such as metal oxides, zeolites, organic polymers, activated carbons, and metal organic frameworks have been applied in NH3 capture, they still show low uptake capacity, low affinities, and instability. Herein, we developed the first case of a highly stable sulfuric acid covalent organic framework (COF), namely TpBD‐(SO3H)2, as NH3 capturer, in which sulfonic acid sites can strongly interact with NH3 molecules, and enhance the performance of NH3 sorption. As a result, TpBD‐(SO3H)2 shows high chemical stability under strong acid and water conditions, an important merit for the potential application in harsh environment. And it also exhibits high ammonia capacity of 11.5 mmol·g−1 at 298 K and 1.0 bar, making it one of the best in all chemically stable NH3 adsorbents up to date. This work thus develops sulfuric acid COF materials as a new platform for ammonia capture and storage. [ABSTRACT FROM AUTHOR]

Thermally activated delayed fluorescence (TADF) was achieved when electron-rich triphenylene (Tpl) donors were confined to a cage-based porous metal-organic framework (MOF) host (NKU-111) composed of electron-deficient 2,4,6-tri(pyridin-4-yl)-1,3,5-triazine (Tpt) acceptor as the ligand. The spatially separated donor and acceptor molecules in a face-to-face stacking pattern generated strong through-space charge transfer (CT) interactions with a small energy splitting between the singlet and triplet excited states (∼0.1 eV), which enabled TADF. The resulting Tpl@NKU-111 exhibited an uncommon enhanced emission intensity as the temperature increased. Extensive steady-state and time-resolved spectroscopic measurements and first-principles simulations revealed the chemical and electronic structure of this compound in both the ground and low-lying excited states. A double-channel (T1, T2) intersystem crossing mechanism with S1 was found and explained as single-directional CT from the degenerate HOMO−1/HOMO of the guest donor to the LUMO+1 of one of the nearest acceptors. The rigid skeleton of the compound and effective through-space CT enhanced the photoluminescence quantum yield (PLQY). A maximum PLQY of 57.36% was achieved by optimizing the Tpl loading ratio in the host framework. These results indicate the potential of the MOFs for the targeted construction and optimization of TADF materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • Low-power non-coherent light-triggered two-photon absorption process with long-lived transition state: consecutive photo-induced electron transfer and triplet triplet annihilation upconversion. • Supramolecular approaches to extending the lifetime of radical anion or triplet state of dye molecules. • Applications in photoredox catalysis, 3D printing, cancer treatment and bioimaging. • The challenges and future directions are proposed. Materials with multi-photon absorption (MPA) feature, are highly desirable for applications such as deep-seated tumor treatment, high spatiotemporal resolution bioimaging, sophisticated micro-nano fabrication, optical data storage, frequency-upconverting laser, and optical limiting. The classical two-photon absorption (TPA) process relies on an extremely short-lived virtue state, leading to the requirement of an ultrahigh power density of femtosecond pulsed laser. To break this application barrier, the key solution is to extending the lifetime of the transition state in TPA. Recently, the operation of TPA with low-power non-coherent excitation (LPNC-TPA) was achieved by leveraging the mono-reduced species (such as radical anion) and the triplet excited state of dye molecules as the transition state with a relatively long lifetime. In this review, the mechanism of these LPNC-TPA processes will first be introduced, followed by the approaches to extend the lifetime of the mono-reduced species and the triplet state. Then, considering its ability to tune the aggregation mode of dye molecules, the metal–organic framework (MOF) will be emphasized as an efficient tool to operate efficient LPNC-TPA in the solid state. The merits and features of LPNC-TPA materials will be revealed through their emerging applications in photoredox catalysis, photopolymerization, 3D printing, in vivo cancer treatment, bioimaging, and biosensing. Finally, the future directions and challenges of LPNC-TPA are proposed, along with the possible solutions. [ABSTRACT FROM AUTHOR]

We developed herein for the first time a sensitizer created defective MOF (SCD-MOF), simultaneously possessing sensitizers and defects as visible-light harvester and electron trapper, respectively, which can synergistically improve the visible-light photocatalysis of polymeric graphitic carbon nitride (g-C 3 N 4). Based on this discovery, the resulting 5.0 wt% FeTCPP⊂UiO-66@g-C 3 N 4 shows a significant 6.6 and 3.9 times improvement in catalytic efficiency compared with its parent materials of FeTCPP⊂UiO-66 and g-C 3 N 4 in degrading organic pollutants. Moreover, it shows a 10.4 times enhancement in catalytic efficiency compared with commercial TiO 2 (P25). Mechanism studies suggest that sensitizer molecules and defects in SCD-MOF can synergistically improve photocatalytic efficiency because of broadening the visible-light response and strengthening the charge carrier separation. This work illustrates a remarkably triple synergetic effect among visible-light harvester, electron/hole separator, and semiconductor and thus established SCD-MOF as a class of new platform to greatly improve the visible-light photocatalytic performance of conventional semiconductors. [Display omitted] • SCD-MOF@g-C 3 N 4 was prepared by a facile thermal treatment route. • The sensitizer molecules inserted in a MOF can create defective sites to boost charge transfer. • The sensitizer molecules in SCD-MOF can act as a light harvester. • The sensitizer molecules and organic ligands within MOFs can adjust band gaps. • The mechanism of photocatalytic degradation were deduced. [ABSTRACT FROM AUTHOR]

Developing universal stimuli‐responsive materials capable of emitting a broad spectrum of colors is highly desirable. Herein, we deliberately grafted a conformation‐adaptable organic chromophore into the established coordination space of a flexible metal–organic framework (MOF). In terms of the coupled structural transformations and the space confinement, the chromophore in the MOF matrix underwent well‐regulated conformational changes under physical and chemical stimuli, simultaneously displaying thermo‐, piezo‐, and solvato‐fluoro‐chromism with color tunability over the visible range. Owing to the resilient nature and the reduced dimensionality of the selected coordination space, all three color modulations behaved in a sensitive and self‐reversible manner, each following a linear correlation of the emission maximum with stimulus. Single‐crystal X‐ray diffraction of the variable‐temperature structures and solvent‐inclusion crystals elucidated the intricate color varying mechanisms. [ABSTRACT FROM AUTHOR]

Developing universal stimuli‐responsive materials capable of emitting a broad spectrum of colors is highly desirable. Herein, we deliberately grafted a conformation‐adaptable organic chromophore into the established coordination space of a flexible metal–organic framework (MOF). In terms of the coupled structural transformations and the space confinement, the chromophore in the MOF matrix underwent well‐regulated conformational changes under physical and chemical stimuli, simultaneously displaying thermo‐, piezo‐, and solvato‐fluoro‐chromism with color tunability over the visible range. Owing to the resilient nature and the reduced dimensionality of the selected coordination space, all three color modulations behaved in a sensitive and self‐reversible manner, each following a linear correlation of the emission maximum with stimulus. Single‐crystal X‐ray diffraction of the variable‐temperature structures and solvent‐inclusion crystals elucidated the intricate color varying mechanisms. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: The sequestration of organic luminescent molecules (OLMs) within cage‐based metal‐organic frameworks (MOFs) as a dispersion platform has been developed to impede aggregation‐caused quenching (ACQ). The homogenous encapsulation of distinct luminescent guests of different sizes and emissive behaviors in the cage structure of a MOF resulted in high fluorescent quantum yields of 44.8% for DAPI@NKU‐110 (DAPI = 4',6‐diamidino‐2‐phenylindole), 65.4% for TPPA@NKU‐110 (TPPA = tris(4‐(pyridin‐4‐ yl)phenyl)amine), 31.3% for R6G@NKU‐110 (R6G = Rhodamine 6G), and 58.3% for PY@NKU‐110 (PY = Pyronin Y), attributable to the confinement effect caused by the rigid cages of NKU‐110. More significantly, a positive correlation of the encapsulated quantity of OLMs with their concentration in the in‐situ solvothermal reaction was unveiled by spectral analysis and utilized to facilely fabricate a white‐light‐emitting crystal material TPPA+R6G@NKU‐110. This material features a large crystal size on the millimeter‐scale, broadband white emission, ideal CIE coordinates (0.33, 0.34), and a high quantum yield (49.1%) when excited at 365 nm. Moreover, such a strategy can be easily generalized to an abundance of other cage‐based MOFs and a plentiful volume of OLMs for the future development of colorful, high performance luminescent materials. [ABSTRACT FROM AUTHOR]

Chiral hybrid organic–inorganic metal halides (HOMHs) with intrinsic noncentrosymmetry have shown great promise for applications in second‐order nonlinear optics (NLO). However, established chiral HOMHs often suffer from their relatively small band gaps, which lead to negative impacts on transparent window and laser‐induced damage thresholds (LDT). Here, we have synthesized two chiral HOMHs based on CuI halides, namely (R‐/S‐MBA)CuBr2, which feature well‐balanced NLO performances with a highly efficient SHG response, outstanding optical transparency, and high LDT. The effective second‐order NLO coefficient of (R‐MBA)CuBr2 has been determined to be ≈24.7 pm V−1, which is two orders of magnitude higher than that of their CuII counterparts. This work shows the promising potential of CuI‐based chiral HOMHs for nonlinear photonic applications in wide wavelength regions. [ABSTRACT FROM AUTHOR]

Chiral hybrid organic–inorganic metal halides (HOMHs) with intrinsic noncentrosymmetry have shown great promise for applications in second‐order nonlinear optics (NLO). However, established chiral HOMHs often suffer from their relatively small band gaps, which lead to negative impacts on transparent window and laser‐induced damage thresholds (LDT). Here, we have synthesized two chiral HOMHs based on CuI halides, namely (R‐/S‐MBA)CuBr2, which feature well‐balanced NLO performances with a highly efficient SHG response, outstanding optical transparency, and high LDT. The effective second‐order NLO coefficient of (R‐MBA)CuBr2 has been determined to be ≈24.7 pm V−1, which is two orders of magnitude higher than that of their CuII counterparts. This work shows the promising potential of CuI‐based chiral HOMHs for nonlinear photonic applications in wide wavelength regions. [ABSTRACT FROM AUTHOR]

We report that the previously reported square lattice coordination network [Ni(4,4′-bipyridine)2(NCS)2]n, sql-1-Ni-NCS, undergoes acetylene induced switching between closed (nonporous) and open (porous) phases. The resulting stepped sorption isotherms exhibit temperature controlled steps, consistent high uptake and benchmark working capacity (185 cm−3 g−1 or 189 cm−3, 1–3.2 bar, 288 K) for acetylene storage. [ABSTRACT FROM AUTHOR]