Traditional semiconducting metal oxide-based gas sensors are always limited on low surface areas and high operating temperatures. Considering the high surface area and high stability of zeolitic ...imidazolate framework (ZIF), ZIF-67 (surface area of 1832.2 m(2) g(-1)) was first employed as a promising formaldehyde gas sensor at a low operating temperature (150 °C), and the gas sensor could detect formaldehyde as low as 5 ppm. This work develops a new promising application approach for porous metal-organic frameworks.
Abstract
ZnIn
2
S
4
(ZIS) is an efficient photocatalyst for solar hydrogen (H
2
) generation from water splitting owing to its suitable band gap, excellent photocatalytic behaviour and high ...stability. Nevertheless, modifications are still necessary to further enhance the photocatalytic performance of ZIS for practical applications. This has led to our interest in exploring phosphorus doping on ZIS for photocatalytic water splitting, which has not been studied till date. Herein, phosphorus-doped ZnIn
2
S
4
(P-ZIS) was modelled via Density Functional Theory to investigate the effects of doping phosphorus on the structural and electronics properties of ZIS as well as its performance toward photocatalytic water splitting. This work revealed that the replacement of S3 atom by substitutional phosphorus gave rise to the most stable P-ZIS structure. In addition, P-ZIS was observed to experience a reduction in band gap energy, an upshift of valence band maximum (VBM), an increase in electron density near VBM and a reduction of H* adsorption–desorption barrier, all of which are essential for the enhancement of the hydrogen evolution reaction. In overall, detailed theoretical analysis carried out in this work could provide critical insights towards the development of P-ZIS-based photocatalysts for efficient H
2
generation via solar water splitting.
Skeletal muscles are natural motors executing sophisticated work through precise control of linear contraction. Although various liquid crystal polymers based artificial muscles have been designed, ...the mechanism based on mainly the order–disorder transition usually leads to discrete shape morphing, leaving arbitrary and precise deformation a huge challenge. Here, one novel photoresponsive hemiphasmidic side‐chain liquid crystal polymer with a unique “breathing” columnar phase that enables continuous morphing is presented. Due to confinement inside the supramolecular columnar assembly, the cooperative movements of side‐chains and backbones generate a significant negative thermal expansion and lead to temperature‐controllable muscle‐like elongation/contraction in the oriented polymer strip. The irreversible isomerization of the photoresponsive mesogens results in the synergistic phototunable bending and high‐contrast fluorescence change. Based on the orthogonal responses to heat and light, controllable arm‐like bending motions of this material, which is applicable in constructing advanced artificial muscles or intelligent soft robotics, are further demonstrated.
A hemiphasmidic side‐chain liquid crystal polymer forms multichain supramolecular columnar assemblies. Through the cooperative movements of main‐chains and side‐chains, the uniaxially aligned polymer strip executes muscle‐like continuous and reversible elongation/contraction. The irreversible photoisomerization of mesogens further endows the polymer strip with arm‐like phototunable bending which can lift heavy load. Both deformations are under precise control of temperature.
A series of zirconium polyphenolate‐decorated‐(metallo)porphyrin metal–organic frameworks (MOFs), ZrPP‐n (n = 1, 2), featuring infinite ZrIV‐oxo chains linked via polyphenolate groups on four ...peripheries of eclipse‐arranged porphyrin macrocycles, are successfully constructed through a top–down process from simulation to synthesis. These are the unusual examples of Zr‐MOFs (or MOFs in general) based on phenolic porphyrins, instead of commonly known carboxylate‐based types. Representative ZrPP‐1 not only exhibits strong acid resistance (pH = 1, HCl) but also remains intact even when immersed in saturated NaOH solution (≈20 m), an exceptionally large range of pH resistance among MOFs. The metallation at the porphyrin core gives rise to materials with enhanced sorption and catalytic properties. In particular, ZrPP‐1‐Co, with precise and uniform distribution of active centers, exhibits not only high CO2 trapping capability (≈90 cm3 g−1 at 1 atm, 273 K, among the highest in Zr‐MOFs) but also high photocatalytic activity for reduction of CO2 into CO (≈14 mmol g−1 h−1) and high selectivity over CH4 (>96.4%) without any cocatalyst under visible‐light irradiation (λ > 420 nm). Given the strong chemical resistance under extreme alkali conditions, these catalysts can be recycled without appreciable loss of activity. The possible mechanism for photocatalytic reduction of CO2‐to‐CO over ZrPP‐1‐Co is also proposed.
Top–down fabrication of robust and porous materials based on infinite ZrIV‐polyphenolate chains linked via eclipsed‐arranged porphyrin macrocycles is presented. Among them, ZrPP‐1 retains its framework integrity when immersed in saturated NaOH solution as long as 1 week. Moreover, metallation at the porphyrin core gives rise to materials with enhanced CO2 trapping capability and high visible‐light‐driven CO2‐to‐CO photoreduction activity.
Two novel two‐dimensional metal–organic frameworks (2D MOFs), 2D‐M2TCPE (M=Co or Ni, TCPE=1,1,2,2‐tetra(4‐carboxylphenyl)ethylene), which are composed of staggered (4,4)‐grid layers based on ...paddlewheel‐shaped dimers, serve as heterogeneous photocatalysts for efficient reduction of CO2 to CO. During the visible‐light‐driven catalysis, these structures undergo in situ exfoliation to form nanosheets, which exhibit excellent stability and improved catalytic activity. The exfoliated 2D‐M2TCPE nanosheets display a high CO evolution rate of 4174 μmol g−1 h−1 and high selectivity of 97.3 % for M=Co and Ni, and thus are superior to most reported MOFs. The performance differences and photocatalytic mechanisms have been studied with theoretical calculations and photoelectric experiments. This study provides new insight for the controllable synthesis of effective crystalline photocatalysts based on structural and morphological coregulation.
As a result of rational structural design and structure‐directed morphology control, two new 2D MOFs underwent photochemically assisted in situ exfoliation to form nanosheets during visible‐light photocatalytic CO2 reduction (see picture). The exfoliated nanosheets displayed a high CO evolution rate and high selectivity for the formation of CO.
Photocatalytic reduction of CO2 has attracted enormous interest as a sustainable and renewable source of energy. In the past decade, numerous bulk‐type semiconductors have been developed, but the ...existing designs suffer many limitations, namely rapid recombination of charge carriers and weak light absorption ability. Herein, a bottom‐up approach was developed to design atomically thin sulfur‐doped Bi2WO6 perovskite nanosheets (S‐BWO) with improved reduction ability, extended visible light absorption, prolonged lifetime of charge carriers, enhanced adsorption of CO2, and reduced work function. Compared with pristine Bi2WO6 (P‐BWO), S‐BWO nanosheets exhibited a 3‐fold improvement in photocatalytic reduction of CO2 under simulated sunlight irradiation. Experimental studies and density functional theory calculations revealed the synergistic roles of atomically thin nanosheets and S atoms in promoting photocatalytic efficiency.
CO2 reduction: Charge modulation of atomically thin perovskite structure containing sulfur dopants promotes photocatalytic carbon dioxide reduction. Experimental results and theoretical calculations reveal the enhanced light absorption ability of the catalyst, elevated conduction band, prolonged lifetime of charge carriers, lower electron transfer resistance, reduced work function, and enhanced adsorption of carbon dioxide.
Two new chemically stable metalloporphyrin‐bridged metal‐catechol frameworks, InTCP‐Co and FeTCP‐Co, were constructed to achieve artificial photosynthesis without additional sacrificial agents and ...photosensitizers. The CO2 photoreduction rate over FeTCP‐Co considerably exceeds that obtained over InTCP‐Co, and the incorporation of uncoordinated hydroxyl groups, associated with catechol, into the network further promotes the photocatalytic activity. The iron‐oxo coordination chain assists energy band alignment and provides a redox‐active site, and the uncoordinated hydroxyl group contributes to the visible‐light absorptance, charge‐carrier transfer, and CO2‐scaffold affinity. With a formic acid selectivity of 97.8 %, FeTCP‐OH‐Co affords CO2 photoconversion with a reaction rate 4.3 and 15.7 times higher than those of FeTCP‐ Co and InTCP‐Co, respectively. These findings are also consistent with the spectroscopic study and DFT calculation.
A series of hydro‐stable metalloporphyrin‐bridged metal‐phenate frameworks are constructed, which exhibit artificial photosynthetic activity under visible‐light irradiation without photosensitizer or sacrificial agent. Activity is boosted by substitution of the Fe‐oxo chain for an In‐oxo chain, and further enhanced by addition of the uncoordinated hydroxyl groups of catechol into the scaffold.
Melatonin (N‐acetyl‐5‐methoxytryptamine) is an important biological hormone in many abiotic stress responses and developmental processes. In this study, the protective roles of melatonin were ...investigated by measuring the antioxidant defense system and photosynthetic characteristics in maize under salt stress. The results indicated that NaCl treatment led to the decrease in plant growth, chlorophyll contents and photochemical activity of photosystem II (PSII). However, the levels of reactive oxygen species increased significantly under salt stress. Meanwhile, we found that application of exogenous melatonin alleviated reactive oxygen species burst and protected the photosynthetic activity in maize seedlings under salt stress through the activation of antioxidant enzymes. In addition, 100 μM melatonin‐treated plants showed high photosynthetic efficiency and salinity. Immunoblotting analysis of PSII proteins showed that melatonin application alleviated the decline of 34 kDa PSII reaction center protein (D1) and the increase of PSII subunit S protein. Taken together, our study promotes more comprehensive understanding in the protective effects of exogenous melatonin in maize under salt stress, and it may be involved in activation of antioxidant enzymes and regulation of PSII proteins.
Photocatalysis is a perennial solution that promises to resolve deep-rooted challenges related to environmental pollution and energy deficit through harvesting the inexhaustible and renewable solar ...energy. To date, a cornucopia of photocatalytic materials has been investigated with the research wave presently steered by the development of novel, affordable, and effective metal-free semiconductors with fascinating physicochemical and semiconducting characteristics. Coincidentally, the recently emerged red phosphorus (RP) semiconductor finds itself fitting perfectly into this category ascribed to its earth abundant, low-cost, and metal-free nature. More notably, the renowned red allotrope of the phosphorus family is spectacularly bestowed with strengthened optical absorption features, propitious electronic band configuration, and ease of functionalization and modification as well as high stability. Comprehensively detailing RP's roles and implications in photocatalysis, this review article will first include information on different RP allotropes and their chemical structures, followed by the meticulous scrutiny of their physicochemical and semiconducting properties such as electronic band structure, optical absorption features, and charge carrier dynamics. Besides that, state-of-the-art synthesis strategies for developing various RP allotropes and RP-based photocatalytic systems will also be outlined. In addition, modification or functionalization of RP with other semiconductors for promoting effective photocatalytic applications will be discussed to assess its versatility and feasibility as a high-performing photocatalytic system. Lastly, the challenges facing RP photocatalysts and future research directions will be included to propel the feasible development of RP-based systems with considerably augmented photocatalytic efficiency. This review article aspires to facilitate the rational development of multifunctional RP-based photocatalytic systems by widening the cognizance of rational engineering as well as to fine-tune the electronic, optical, and charge carrier properties of RP.
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