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Graphitic carbon nitride (g-C3N4) is an organic semiconductor for photocatalysis. However, it still suffers from low surface area and rapid e–/h+ recombination, which limits its further activity enhancement. In this work, an atomically precise alkynyl- and phosphine-protected Ag33(4-MePhCC)22(Dppp)4 nanocluster is synthesized. It is facilely loaded onto g-C3N4 nanosheets by a one-step process. The resulting Ag33/g-C3N4 nanocomposite is thoroughly characterized. Its activity is evaluated in the photodegradation of methyl orange. Ag33/g-C3N4 has shown a 16-fold activity enhancement compared to pristine g-C3N4. The mechanism investigation using UV–vis/diffuse-reflectance spectroscopy spectra, photocurrent response, and Nyquist plots has revealed the origin of this superior performance. [ABSTRACT FROM AUTHOR]

High-performance nonlinear-optical (NLO) crystals need to simultaneously meet multiple basic and conflicting performance requirements. Here, by using a partial chemical substitution strategy, the first noncentrosymmetric (NCS) PbBeB 2 O 5 crystal with a BeB 2 O 8 group was synthesized, exhibiting a two-dimensional [BeB 2 O 5 ] ∞ layer constructed by interconnecting BeB 2 O 8 groups and bridged PbO 4 with an active lone pair. The crystal shows a promising UV NLO functional feature, including a strong SHG effect of 3.5 × KDP (KH 2 PO 4 ), large birefringence realizing phase matchability in the whole transparency region from 246 to 2500 nm, a short UV absorption edge of 246 nm, and single-crystal easy growth. Remarkably, theoretical studies reveal that the BeB 2 O 8 group has high nonlinear activity, which could stimulate the discovery of a series of excellent NLO beryllium borates.

Atoms in special lattice sites can play a crucial role in realizing materials properties, which is long pursued but difficult to control. Herein, by adopting a stereochemically active lone-pair-containing metal substitution strategy, a nonlinear-optical (NLO) silicate crystal Li 3 (OH)PbSiO 4 was successfully synthesized, featuring [PbSiO 4 ] ∞ layers with the perfect orientation of the stereochemically active lone-pair Pb(II) cation in the polar-axis lattice. Li 3 (OH)PbSiO 4 overcomes the long-standing problem of silicates, that is, poor nonlinear properties because it exhibits both the largest birefringence of 0.082 and the largest phase-matchable second-harmonic-generation (SHG) efficiency of 21 × KDP among the known silicates. The successful polar-axis lattice substitution could offer a new direction for realizing the rational control of materials structures and properties.

Stereochemically active lone-pair (SCALP) cations are one attractive type of nonlinear optical (NLO)-active units because of their large microcosmic polarizability and anisotropy. Currently, the single and/or dual lone-pair cation-based noncentrosymmetric (NCS) oxides have been extensively investigated and verified to be one class of outstanding NLO materials. From the perspective of function optimization, the integration of three kinds of SCALP cations into one crystal may synergistically improve the NLO properties, which is greatly expected but unexplored to date. Herein, by introducing flexible metal halide bonds to guarantee the stereochemical activity and overcome the energetically favorable antiparallel arrangements of lone-pair cations, the first type of three lone-pair-cation (Pb 2+ , Bi 3+ , and Se 4+ )-coexisting NCS oxides PbBi(SeO 3 ) 2 F ( I ) and Pb 2 Bi(SeO 3 ) 2 Cl 3 ( II ) was obtained. As expected, both compounds show outstanding NLO properties, such as the strong second-harmonic-generation signal (10.5× and 13.5 × KDP), large birefringence (0.103 and 0.186), relatively wide energy band gaps (3.75 and 3.45 eV), and good physicochemical stability. Theoretical calculations demonstrated the effect of three lone-pair-cation-based polyhedra and the halide anion on NLO properties.

The high-valence tin-oxo clusters are of great significance because of their structural diversity and potential applications in many fields, e.g., catalysis, extreme ultraviolet (EUV) lithography, and so on. The synthesis of high-nuclearity tin-oxo clusters remains a great challenge currently, since the key inorganic Sn x O y core with Sn 4+ ions could not be obtained only by the in situ Sn-C bond cleavage in organic tin sources. In this context, we synthesize three organic-inorganic hybrid Sn 18 -oxo clusters, [(BuSn) 12 Sn 6 (μ 3 -O) 20 (ba) 12 (PhPO 3 ) 4 ] (Bu = butyl, Hba = benzoic acid), [(BuSn) 12 Sn 6 (μ 3 -O) 20 (pmba) 12 (PhPO 3 ) 4 ]·2CH 3 CN·2H 2 O (Hpmba = p -toluic acid), and [(BuSn) 12 Sn 6 (μ 3 -O) 20 (ptba) 12 (PhPO 3 ) 4 ]·2CH 3 CN·2 i PrOH·2H 2 O (Hptba = p -tert-butyl benzoic acid), as well as one Sn 6 -oxo cluster [(BuSn) 6 (μ 3 -O) 2 (μ 2 -OH) 4 (pnba) 6 (PhPO 3 ) 2 ] (Sn 6 ) (Hpnba = p -nitrobenzoic acid) by combining an inorganic precursor (SnCl 4 ) with an organic one (butyltin hydroxide oxide). It is shown that an inorganic dicyclo-chain-like Sn 6 O 8 core encapsulated in a U-shaped dodecanuclear butyltin-oxo ring plays an important role in the construction of Sn 18 -oxo clusters and that the use of a ligand with an electron-withdrawing group reduces the nuclearity of clusters to Sn 6 . Moreover, electrocatalytic CO 2 reduction studies confirm that the electrocatalytic activities of the Sn 18 clusters are superior to those of the Sn 6 cluster, probably due to the hybrid organotin-inorganotin structures. Our work not only opens a new way for constructing high-nuclearity tin-oxo clusters but also is helpful in deeply revealing the structure-properties relationship of tin-oxo clusters.

The exploration of nonlinear-/linear-optical crystal materials with high performance is an extremely difficult research project. Herein, the two new lead tellurite crystals BaPbTe 2 O 6 and PbVTeO 5 F were successfully obtained through a facile hydrothermal synthesis strategy. BaPbTe 2 O 6 lies in the noncentrosymmetric (NCS) and chiral orthorhombic space group P 2 1 2 1 2 1 , featuring a unique ∞ 1 [PbTe 2 O 6 ] chain consisting of the PbO 4 and TeO 3 building units, while PbVTeO 5 F belonging to the centrosymmetric (CS) orthorhombic space group Pbca manifests a 2D layer made up of ∞ 1 [PbO 4 F 2 ] chains and novel [V 2 Te 2 O 10 F 2 ] clusters. Further, a systematic analysis of lead tellurites finds that the coordination geometries of the Pb atom exert a considerable influence on the connection modes of Pb-O and Te-O building units. BaPbTe 2 O 6 shows a great second-harmonic-generation (SHG) effect of ∼5× the benchmark KH 2 PO 4 (KDP) and a large optical birefringence of 0.086 at 590 ± 3 nm. PbVTeO 5 F demonstrates a remarkably larger birefringence of 0.142 at 590 ± 3 nm, benefiting from the introduction of the VO 5 F octahedral unit. Theoretical studies reveal that the large SHG and birefringence in BaPbTe 2 O 6 can be attributed to TeO 3 and PbO 4 polyhedra with active lone pairs, while the remarkably enlarged birefringence in PbVTeO 5 F is attributable to the highly distorted octahedral VO 5 F. The functional orientations of active building units may offer a practical insight into the design of the desired optical functional materials.

Introducing transition metals into the intercluster linkers has been considered an important strategy for the rapid development of metal chalcogenide supertetrahedral (T n ) cluster-based open frameworks with excellent properties. However, using this strategy for achieving the structure and property tunability in the cluster-based framework of T n ( n ≥ 5) is still a great challenge. Herein, we report on three new sulfide and oxosulfide open frameworks of T5 clusters, i.e., T5-ZnMnInOS ([In 30 Zn 5 Mn 4 O 2 S 58 ] 12- ), T5-MnInOS ([In 34 Mn 5 O 2 S 58 ] 8- ), and T5-MnInS ([In 28 Mn 6 S 54 ] 12- ). Interestingly, transition metals Zn and Mn are successfully introduced into T5-ZnMnInOS and T5-MnInOS via the consolidation of corner-shared Zn 2 OS 2 and Mn 2 OS 2 units, respectively. Under the photoexcitation of UV light, three compounds can emit bright-orange-red light closely associated with the Mn 2+ ions, and the compounds containing M 2 OS 2 units exhibit better photoluminescence (PL) lifetimes. Variable-temperature PL spectra demonstrate that the introduced M 2 OS 2 units are favorable for weakening the deformation of the skeleton structure and decreasing the red shifts of the emission peaks at low temperatures. Moreover, the experimental results exhibit that the three compounds are wide-band-gap semiconductors and that the photogenerated electron separation efficiency can be doubly increased because the intercluster linkers are fixed by the M 2 OS 2 units. This work paves a new way for enriching the content and distribution types of transition-metal sites in the supertetrahedral cluster-based metal chalcogenide open frameworks.

One-dimensional (1D) organic-inorganic hybrid lead halides with unique core-shell quantum wire structures and splendid photoluminescence properties have been considered one of the most promising high-efficiency broadband emitters. However, studies on the broadband emissions in 1D purely face-shared lead iodide hybrids are still rare so far. Herein, we report on a new 1D lead iodide hybrid, (2cepyH)PbI 3 (2cepy = 1-(2-chloroethyl)pyrrolidine), characterized with face-sharing PbI 6 octahedral chains. Upon UV photoexcitation, this material shows broadband yellow emissions originating from the self-trapped excitons associated with distorted Pb-I lattices on account of the strong exciton-phonon coupling, as proved by variable-temperature emission spectra. Moreover, experimental and calculated results reveal that (2cepyH)PbI 3 is an indirect bandgap semiconductor, the band structures of which are governed by inorganic parts. Our work represents the first broadband emitter based on a 1D face-shared lead iodide hybrid and opens a new way to obtain the novel broadband emission materials.

Chromium(III)-based metal-organic frameworks (Cr-MOFs) are highly robust and porous and have been very attractive in a wide range of investigations. However, the harsh direct synthetic conditions not only impede the synthesis of new Cr-MOFs but also restrict the introduction of functional groups into them. Postsynthetic modification has somewhat alleviated such difficulties; nevertheless, it still suffered from procedures that are tedious and conditions that are not mild, which often result in low concentration of the functional groups introduced. To overcome these shortcomings, here, in this paper, we supplied a new route and prepared a benzyl alcohol functionalized Cr-SXU-2 from the judiciously designed benzyl alcohol functionalized Fe-SXU-2 through solvent-assisted metal metathesis strategy. The functionalized Cr-SXU-2 shows well-preserved crystallinity, porosity, and high chemical stability. The benzyl alcohol group can be converted into a very active benzyl bromide group in an almost quantitative yield and thus for the first time produce the benzyl bromide functionalized MOF, Cr-SXU-2-Br , in which the -Br group can be exchanged by a nucleophilic group. As a proof of concept, -N 3 was introduced and transformed into other active sites via "click reaction" to further tailor the interior of Cr-SXU-2 . All these functionalized Cr-MOFs showed improved adsorption performance in contrast to the nonfunctionalized one. This step-by-step postmodification process not only diversifies the functionalization of robust MOFs but also opens a new route to employ many different functional groups in the demanding highly stable Cr-MOF platforms.

The design of material by chemical and/or crystalline modification of a classic structure model benefits not only the optimized physical properties but also the controllability and efficiency. Herein, a new nonlinear-optical (NLO) beryllium borate crystal, Sr 2 Pb(BeB 5 O 10 )(BO 3 ) (SPBBO), is successfully designed and synthesized by chemical and crystalline modification of the perovskite-like K 3 B 6 O 10 Cl NLO crystal. SPBBO displays a 3D BeB 5 O 10 3- open-framework structure composed of interconnecting BeB 5 O 13 groups with filled cationic Sr/Pb and anionic BO 3 groups, which exhibits the striking enhancement of the second-harmonic-generation (SHG) response (8 × KDP) and birefringence (0.10) compared to the parent model. Replacement of K by Sr and Pb with a lone pair and replacement of Cl by conjugated BO 3 result in the synergistic conjugation of Pb with host BeB 5 O 10 3- and filled BO 3 groups, contributing to the striking enhancement of the SHG and birefringence. Single-crystal measurements show that SPBBO has a short UV absorption edge of 280 nm with a wide energy band gap of 4.35 eV and an outstanding laser-induced resistant behavior with a remarkably high laser-induced damage threshold of 2100 MW cm -2 . The excellent properties indicate that the SPBBO crystal is a very promising UV NLO functional material.

Titanium-oxide or polyoxotitanate clusters are a new type of inorganic host materials that can encapsulate inorganic molecules or ions. We report herein a (NH 4 ) 4 (enH 2 )[Ti 18 O 27 (PhCOO) 24 (en) 9 ] molecular cage (Ti 18 ) that encapsulates an entire organic ethylenediamine (en) ion. A thorough investigation has revealed the extraordinary versatility of en. Besides being a guest cation, it also functions as chelating and bridging ligand. It balances the charge of the negative Ti 18 cage and facilitates the deprotonation of benzoic acid at the early stage of the reaction as well. DFT calculation and a derivative of Ti 18 with open sites at its equatorial position shed further light on the formation mechanism. Ti 18 strongly absorbs visible light as a result of en coordination, and it exhibits superior photocatalytic activity compared to anatase TiO 2 .

Rational design and controllable synthesis of efficient and robust electrocatalysts for hydrogen evolution reaction (HER) remain a critical challenge for the renewable energy economy. Herein, heterostructured Nb 4 N 5- x O x -MoS 2 (0 < x < 1) anchored on N-doped graphene (defined as Nb 4 N 5- x O x -MoS 2 /NG) is synthesized by hydrothermal and chemical vapor deposition (CVD) approaches. During the CVD process, MoS 2 nanosheets are etched into small pieces and covalently interconnected with Nb 4 N 5- x O x to form fine Nb 4 N 5- x O x -MoS 2 heterostructures, which possess abundant interfaces and fully exposed edge active sites. The as-prepared Nb 4 N 5- x O x -MoS 2 heterostructures with Nb-(N,S)-Mo bridges provide desired electron density, which exhibit excellent chemisorption ability for both H and water, significantly improving the intrinsic HER activity. Meanwhile, the covalently connected Nb 4 N 5- x O x -MoS 2 heterostructures together with chemical coupling of Nb 4 N 5- x O x -MoS 2 and N-doped graphene improve the structural stability and ensure fast electron transfer in the Nb 4 N 5- x O x -MoS 2 /NG nanocomposite, further supporting the H 2 generation and stability.

In this paper, we synthesized three Zr-MOFs (Zr-SXU-1, Zr-SXU-2, and Zr-SXU-3) composed of identical ligands and metal clusters by using tetratopic carboxylic ligand PBPTTBA as the ligand and benzoic acids as modulators. These three Zr-MOFs showed different structures and topologies, and the connectivity of the Zr clusters varied from 8 in Zr-SXU-3, to 10 in Zr-SXU-1, and finally to 12 in Zr-SXU-2 due to the modulators used. Among them, Zr-SXU-1 represents an unusual 6-node network and [6(10)(11)7] transitivity. Besides, Zr-SXU-2 can only be obtained by using ditopic carboxylic acid as a second modulator when using benzoic acid as the main modulator, which is not reported in other Zr-MOFs synthesis. The adsorption and luminescence tests demonstrated their potential as gas reservoirs, separators, and sensors and also showed the importance of structure topologies to the applications.

Sensitization with dyes is the most promising option to narrow the band gap and improve visible-light absorption of TiO 2 . As ideal structure and reaction models of TiO 2 , titanium oxo clusters (TOCs) with exact crystal structure are beneficial for further understanding the structure-property relationship of TiO 2 . Most reports mainly focus on the synthesis and properties of TOCs, but research on the band-gap tuning of TOCs at the large range of 3.7-2.0 eV by chromophore ligands (CLs) has been lacking. Herein, six new Ti 6 -core-based TOCs (Ti 6 -TOCs) were successfully synthesized by using CLs in a simple and general approach. Each Ti 6 -TOC structure contains two Ti 3 (μ 3 -O) units featuring a flat or pyramidal mode as building blocks. Five Ti 6 -core structure types were present among the six Ti 6 -TOCs, which enriched the family of hexanuclear TOCs. To be noted, the band-gap values were tuned at a wide range of 3.41-1.98 eV by controlling the type and number of the CLs 2-hydroxypyridine, salicylaldoxime, and catechol in the structure. Density functional theory calculation revealed that the lowest-energy bands of these Ti 6 -TOCs are attributed to the CL-to-TiO core charge-transfer bands. This work provides a precise and wide-ranged band-gap tuning method for TOCs. Additionally, the six Ti 6 -TOCs exhibit good photocurrent response.

Smart materials are highly desirable over the recent decade due to the growing demand of complicated nature. Stable stimuli-responsive smart materials exhibit widespread potential for applications in smart windows, sensors, separators, chemical valves, and release platforms but are rare. Despite being good candidates, viologen-based multifunctional smart materials are still a challenging task for chemists. To obtain such materials, the judicious strategy is to introduce polynuclear metal-carboxylate clusters as electron donors into a stable framework to increase chromic sensitivity. Toward this endeavor, we have synthesized a novel viologen-based polymer with a unique Anderson-like metal-carboxylate cluster, [Zn 7 (bpybc) 3 (o-BDC) 6 ]·2NO 3 ·6H 2 O (bpybc = 1,1'-bis(4-carboxyphenyl)-4,4'-bipyridinium, o-BDC = o -benzenedicarboylic acid) ( 1 ), which is a particular 7-fold interpenetrated framework with a 3D pcu network in which bpybc ligand as the linker and Zn 7 O 30 C 12 as the second building unit (Zn 7 SBU) were used as 6-connected nodes. More importantly, it shows excellent chromic behavior in response to multiple external stimuli especially soft X-ray and UV dual light, temperature, electricity, and organic amines, which stand out in the viologen-based polymers. Interestingly, the coloration process of 1 from "core" to "edge" is observed upon heating at the appropriate temperature, which has not yet been found in other reported thermochromic materials. Of particular interest for 1 is the couple of quaternary stimuli-sensitive abilities because it simultaneously meets the following conditions: (i) the capability of withstanding high light, higher temperature, extreme pH, and other harsh conditions; and (ii) the high sensitivity to external stimuli keeping away from photodegradation, thermal relaxation, side reactions, and so on. To be noted, 1 has high thermal stability and chemical stability, which are excellent advantages as smart materials. To further develop possible practical utilization, 1 has been doped into the polymer matrixes to construct a hybrid film, which not only keeps the response to external stimuli but also significantly improves the repeatability of the photochromic process, indicating that a new smart device with multi-stimuli-responsive functions will emerge successively in the future.