Explore the vast range of titles available.

Metal-organic framework (MOF) nanosheets and covalent organic framework (COF) nanosheets as emerging porous materials nanosheets have captured increasing attention owing to their attractive properties originating from the advantages of large lateral size, ultrathin thickness, tailorable physiochemical environment, flexibility and highly accessible active sites on surface, and the applications of them have been explored in a wide range of fields. Although MOF and COF nanosheets own many similar properties, their applications in various fields show significant differences, probably due to their different compositions and bonding modes. Hence, we summarize the recent progress of MOF and COF nanosheets by comparative analysis on their advantages and limitations in synthesis and applications, providing a more profound and full-scale perspective for researchers or beginners to understand this field. Herein, the categories of preparation methods of MOF and COF nanosheets are firstly discussed, including top-down and bottom-up methods. Secondly, the applications of MOF and COF nanosheets for separation, catalysis, sensing and energy storage are summarized. Finally, based on current achievements, we put forward our personal insights into the challenges and outlooks on the synthesis, characterizations, and promising applications for future research of MOF and COF nanosheets.

Materials exhibiting long-lived, persistent luminescence in the visible spectrum are useful for applications in the display, information encryption and bioimaging sectors1–4. Herein, we report the development of several organic phosphors that provide colour-tunable, ultra-long organic phosphorescence (UOP). The emission colour can be tuned by varying the excitation wavelength, allowing dynamic colour tuning from the violet to the green part of the visible spectrum. Our experimental data reveal that these organic phosphors can have an ultra-long lifetime of 2.45 s and a maximum phosphorescence efficiency of 31.2%. Furthermore, we demonstrate the applications of colour-tunable UOP for use in a multicolour display and visual sensing of ultraviolet light in the range from 300 to 360 nm. The findings open the opportunity for the development of smart luminescent materials and sensors with dynamically controlled phosphorescence.Organic phosphors with ultra-long lifetimes and an emission colour that can be tuned by the excitation wavelength are reported.

Flexible electronics are playing an increasingly important role in human health monitoring and healthcare diagnosis. Strong adhesion on human tissue would be ideal for reducing interface resistance and motion artifacts, but arising problems such as skin irritation, rubefaction, and pain upon device removal have hampered their utility. Here, inspired by the temperature reversibility of hydrogen bonding, a skin-friendly conductive hydrogel with multiple-hydrogen bonds was designed by using biocompatible poly(vinyl alcohol) (PVA), phytic acid (PA), and gelatin (Gel). The obtained PVA/PA/Gel (PPG) hydrogel with temperature-triggered tunable mechanic could reliably adhere to skin and detect electrophysiological signals under a hot compress while be readily removed under a cool compress. Furthermore, the additional advantages of transparency, breathability, and antimicrobial activity of the PPG hydrogel ensure its long-time wearable value on the skin. It is both environmentally friendly and cost saving for the waste PPG hydrogel during production can be recycled based on their reversible physical bonding. The PPG hydrogel sensor is expected to have good application prospects to record electrophysiological signals in human health monitoring.

Dynamic luminescence behavior by external stimuli, such as light, thermal field, electricity, mechanical force, etc., endows the materials with great promise in optoelectronic applications. Upon thermal stimulus, the emission is inevitably quenched due to intensive non-radiative transition, especially for phosphorescence at high temperature. Herein, we report an abnormal thermally-stimulated phosphorescence behavior in a series of organic phosphors. As temperature changes from 198 to 343 K, the phosphorescence at around 479 nm gradually enhances for the model phosphor, of which the phosphorescent colors are tuned from yellow to cyan-blue. Furthermore, we demonstrate the potential applications of such dynamic emission for smart dyes and colorful afterglow displays. Our results would initiate the exploration of dynamic high-temperature phosphorescence for applications in smart optoelectronics. This finding not only contributes to an in-depth understanding of the thermally-stimulated phosphorescence, but also paves the way toward the development of smart materials for applications in optoelectronics. In thermally stimulated phosphorescent materials a thermal stimulus inevitably quenches the emission due to intensive non radiative transition. Here, the authors report an abnormal thermally stimulated phosphorescence behavior in organic phosphors and show enhancement of phosphorescence and change of the emission color upon temperature increase.

Composites incorporating metal nanoparticles (MNPs) within metal-organic frameworks (MOFs) have broad applications in many fields. However, the controlled spatial distribution of the MNPs within MOFs remains a challenge for addressing key issues in catalysis, for example, the efficiency of catalysts due to the limitation of molecular diffusion within MOF channels. Here we report a facile strategy that enables MNPs to be encapsulated into MOFs with controllable spatial localization by using metal oxide both as support to load MNPs and as a sacrificial template to grow MOFs. This strategy is versatile to a variety of MNPs and MOF crystals. By localizing the encapsulated MNPs closer to the surface of MOFs, the resultant MNPs@MOF composites not only exhibit effective selectivity derived from MOF cavities, but also enhanced catalytic activity due to the spatial regulation of MNPs as close as possible to the MOF surface. Composites incorporating metallic nanoparticles into metal-organic frameworks are potentially useful but controlling the nanoparticle spatial distribution is challenging. Here, the authors report a strategy that accomplishes this by using a metal oxide as both support and sacrificial template.

Hydrogen spillover is the migration of activated hydrogen atoms from a metal particle onto the surface of catalyst support, which has made significant progress in heterogeneous catalysis. The phenomenon has been well researched on oxide supports, yet its occurrence, detection method and mechanism on non-oxide supports such as metal–organic frameworks (MOFs) remain controversial. Herein, we develop a facile strategy for efficiency enhancement of hydrogen spillover on various MOFs with the aid of water molecules. By encapsulating platinum (Pt) nanoparticles in MOF-801 for activating hydrogen and hydrogenation of C=C in the MOF ligand as activated hydrogen detector, a research platform is built with Pt@MOF-801 to measure the hydrogenation region for quantifying the efficiency and spatial extent of hydrogen spillover. A water-assisted hydrogen spillover path is found with lower migration energy barrier than the traditional spillover path via ligand. The synergy of the two paths explains a significant boost of hydrogen spillover in MOF-801 from imperceptible existence to spanning at least 100-nm-diameter region. Moreover, such strategy shows universality in different MOF and covalent organic framework materials for efficiency promotion of hydrogen spillover and improvement of catalytic activity and antitoxicity, opening up new horizons for catalyst design in porous crystalline materials. Hydrogen spillover in MOFs is a debated research topic. Here the authors design a research platform for evaluating hydrogen spillover in MOFs and investigate water molecules how to assistant active hydrogen to improve hydrogen spillover in MOFs.

Sweat is a biofluid with rich information that can reflect an individual’s state of health or activity. But the real-time in situ sweat sensors lack the ability of long-term monitoring. Against this background, this article provides a holistic review on the necessary process and methods for sweat sensing, including sweat collection, composition analysis, energy supply, and data processing. The impacts of the environment in stimulating sweat production, providing energy supply, and intelligent health monitoring are discussed. Based on the review of previous endeavors, the future development in material, structure and artificial intelligence application of long-term sweat monitoring is envisioned.

Covalent organic frameworks are attractive candidates for the next generation films in technical applications. However, due to their crystallization nature, insolubility in common solvents as well as infusible at high temperatures make it challenging to grow them spontaneously or process them into films. Herein, we report an efficient strategy to fabricate covalent organic framework films based on a modulator-solvent induced polymerization process. The addition of modulator slows down the nucleation rate during the initial stages of covalent organic framework growth, resulting in the formation of fluidic precursors that are easy to process. Subsequently, a suitable drying process is introduced to balance the evaporation rate of solvent and the crystallization rate of modulator induced, resulting in the formation of covalent organic framework films with a mixture of amorphous and crystalline structures. This strategy is universal for the fabrication of several types of covalent organic framework films with large-scale and freestanding state. Moreover, covalent organic framework films with asymmetric structure can function as organic vapor-triggered actuators, offering excellent repeatability and reversibility. By introducing functional molecules such as fluorescence, chirality and catalyst during the nucleation process, versatile functional covalent organic framework films can be easily fabricated, which endow them with broader application prospects. Covalent organic frameworks are interesting candidates for the next generation films in technical applications, but it is challenging to process them into films. Here, the authors show that introducing functional molecules during the nucleation process, functional covalent organic framework films can be easily fabricated, thereby expanding their potential applications.

Fully π-conjugated polymers with rigid aromatic units are promising for flexible optoelectronic devices, but their inherent brittleness poses a challenge for achieving high-performance, intrinsically stretchable fully π-conjugated polymer. Here, we are establishing an external-plasticizing strategy using semiconductor fluid plasticizers (Z1 and Z2) to enhance the optoelectronic, morphological, and stretchable properties of fully π-conjugated polymer films for flexible light-emitting diodes. The synergistic effect of hierarchical structure and optoelectronic properties of Z1 in poly(9,9-di-n-octylfluorene-alt-benzothiadiazole) (F8BT) films enable excellent stretchable deformability (~25%) and good conductivity. PLEDs based on F8BT/Z1 films show stable electroluminescence and efficiency under 15% stretch and 100 cycles at 10% strain, revealing outstanding stress tolerance. This strategy is also improving the stretchable properties of polymers like poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PFO) and poly(2-methoxy-5(2′-ethyl)hexoxy-phenylenevinylene) (Super Yellow), demonstrating its general applicability. Therefore, this strategy can provide effective guidance for designing high-performance stretchable fully π-conjugated polymers films for flexible electronic devices. The realization of intrinsically stretchable fully π-conjugated polymer film is challenging due to their inherent brittle nature. Here, authors apply semiconductor fluid molecular plasticizers to improve stretchable deformability, achieving high performance flexible polymer light-emitting diodes.

Microporous metal–organic frameworks (MOFs) that display permanent porosity show great promise for a myriad of purposes. The potential applications of MOFs can be developed further and extended by encapsulating various functional species (for example, nanoparticles) within the frameworks. However, despite increasing numbers of reports of nanoparticle/MOF composites, simultaneously to control the size, composition, dispersed nature, spatial distribution and confinement of the incorporated nanoparticles within MOF matrices remains a significant challenge. Here, we report a controlled encapsulation strategy that enables surfactant-capped nanostructured objects of various sizes, shapes and compositions to be enshrouded by a zeolitic imidazolate framework (ZIF-8). The incorporated nanoparticles are well dispersed and fully confined within the ZIF-8 crystals. This strategy also allows the controlled incorporation of multiple nanoparticles within each ZIF-8 crystallite. The as-prepared nanoparticle/ZIF-8 composites exhibit active (catalytic, magnetic and optical) properties that derive from the nanoparticles as well as molecular sieving and orientation effects that originate from the framework material. Surfactant-capped nanoparticles of various sizes, shapes and compositions have been completely enshrouded within a metal–organic framework in a controlled, well-dispersed manner. The resulting hybrid materials exhibit active properties — catalytic, magnetic and optical — arising from the nanoparticles as well as sieving and orientation effects originating from the porous framework.