Mimicking biological proton pumps to achieve stimuli‐responsive protonic solids has long been of great interest for their diverse applications in fuel cells, chemical sensors, and bio‐electronic ...devices. Now, dynamic light‐responsive metal–organic framework hybrid membranes can be obtained by in situ encapsulation of photoactive molecules (sulfonated spiropyran, SSP), as the molecular valve, into the cavities of the host ZIF‐8. The configuration of SSP can be changed and switched reversibly in response to light, generating different mobile acidic protons and thus high on/off photoswitchable proton conductivity in the hybrid membranes and device. This device exhibits a high proton conductivity, fast response time, and extremely large on/off ratio upon visible‐light irradiation. This approach might provide a platform for creating emerging smart protonic solids with potential applications in the remote‐controllable chemical sensors or proton‐conducting field‐effect transistors.
Light‐regulated proton conduction in MOF membranes was realized by in situ encapsulation of light‐active molecules into 3D frameworks. The hybrid membrane has high proton conductivity and outstanding switchable properties, making it feasible to control the lightening of a LED lamp assembled into an optically controlled circuit.
The conversion of CO2 into multicarbon (C2+) compounds by reductive homocoupling offers the possibility to transform renewable energy into chemical energy carriers and thereby create “carbon‐neutral” ...fuels or other valuable products. Most available studies have employed heterogeneous metallic catalysts, but the use of molecular catalysts is still underexplored. However, several studies have already demonstrated the great potential of the molecular approach, namely, the possibility to gain a deep mechanistic understanding and a more precise control of the product selectivity. This Minireview summarizes recent progress in both the thermo‐ and electrochemical reductive homocoupling of CO2 toward C2+ products mediated by molecular catalysts. In addition, reductive CO homocoupling is discussed as a model for the further conversion of intermediates obtained from CO2 reduction, which may serve as a source of inspiration for developing novel molecular catalysts in the future.
This Minireview summarizes recent progress in molecular catalysis of CO2 and CO homocoupling through thermochemical and electrochemical reductive approaches. Particular attention is paid to C−C coupling processes that generate multicarbon products. The current challenges in this rapidly growing field are described and perspectives for possible future developments are outlined.
Producing affordable freshwater has been considered as a great societal challenge, and most conventional desalination technologies are usually accompanied with large energy consumption and thus ...struggle with the trade‐off between water and energy, i.e., the water–energy nexus. In recent decades, the fast development of state‐of‐the‐art photothermal materials has injected new vitality into the field of freshwater production, which can effectively harness abundant and clean solar energy via the photothermal effect to fulfill the blue dream of low‐energy water purification/harvesting, so as to reconcile the water–energy nexus. Driven by the opportunities offered by photothermal materials, tremendous effort has been made to exploit diverse photothermal‐assisted water purification/harvesting technologies. At this stage, it is imperative and important to review the recent progress and shed light on the future trend in this multidisciplinary field. Here, a brief introduction of the fundamental mechanism and design principle of photothermal materials is presented, and the emerging photothermal applications such as photothermal‐assisted water evaporation, photothermal‐assisted membrane distillation, photothermal‐assisted crude oil cleanup, photothermal‐enhanced photocatalysis, and photothermal‐assisted water harvesting from air are summarized. Finally, the unsolved challenges and future perspectives in this field are emphasized. It is envisioned that this work will help arouse future research efforts to boost the development of solar‐driven low‐energy water purification/harvesting.
As a promising candidate to reconcile the water–energy nexus, solar‐driven low‐energy water purification/harvesting technologies have attracted increased attention. The latest progress, challenges, and prospective of engineering solar‐driven photothermal materials/devices and their potential applications are discussed, stimulating new thinking on the exploration of advanced technologies to fulfill the blue dream of low‐energy water purification/harvesting.
Formaldehyde (HCHO) is a crucial C1 building block for daily‐life commodities in a wide range of industrial processes. Industrial production of HCHO today is based on energy‐ and cost‐intensive ...gas‐phase catalytic oxidation of methanol, which calls for exploring other and more sustainable ways of carrying out this process. Utilization of carbon dioxide (CO2) as precursor presents a promising strategy to simultaneously mitigate the carbon footprint and alleviate environmental issues. This Minireview summarizes recent progress in CO2‐to‐HCHO conversion using hydrogenation, hydroboration/hydrosilylation as well as photochemical, electrochemical, photoelectrochemical, and enzymatic approaches. The active species, reaction intermediates, and mechanistic pathways are discussed to deepen the understanding of HCHO selectivity issues. Finally, shortcomings and prospects of the various strategies for sustainable reduction of CO2 to HCHO are discussed.
This Minireview summarizes recent progress in the production of HCHO from CO2, including chemical catalysis (hydrogenation using H2 and hydroboration/hydrosilylation), photo/electrocatalysis, and biocatalysis (enzymatic reduction). From analysis of advantages and deficits of each methodology, we present viewpoints and potential strategies for optimizing the CO2‐to‐HCHO conversion.
Molecular copper catalysts have emerged as promising candidates for the electrochemical reduction of CO2. Notable features of such systems include the ability of Cu to generate C2+ products and the ...well‐defined active sites that allow for targeted structural tuning. However, the frequently observed in situ formation of Cu nanoclusters has undermined the advantages of the molecular frameworks. It is therefore desirable to develop Cu‐based catalysts that retain their molecular structures during electrolysis. In this context, a heterogenized binuclear hydroxo‐bridged phenanthroline Cu(II) compound with a short Cu···Cu distance is reported as a simple yet efficient catalyst for electrogeneration of ethylene and other C2 products. In an aqueous electrolyte, the catalyst demonstrates remarkable performance, with excellent Faradaic efficiency for C2 products (62%) and minimal H2 evolution (8%). Furthermore, it exhibits high stability, manifested by no observable degradation during 15 h of continuous electrolysis. The preservation of the atomic distribution of the active sites throughout electrolysis is substantiated through comprehensive characterizations, including X‐ray photoelectron and absorption spectroscopy, scanning and transmission electron microscopy, UV–vis spectroscopy, as well as control experiments. These findings establish a solid foundation for further investigations into targeted structural tuning, opening new avenues for enhancing the catalytic performance of Cu‐based molecular electrocatalysts.
Numerous studies have shown that copper‐based materials are promising catalysts for electroreductive coupling of CO2. However, a frequent problem is the generation of large amounts of hydrogen as a byproduct. In this context, a binuclear copper phenanthroline complex is presented which, in heterogenized form, generates ethylene and other C2 products in an aqueous electrolyte with minimal H2 formation.
Supported ionic liquid membranes (SILMs), owing to their capacities in harnessing physicochemical properties of ionic liquid for exceptional CO2 solubility, have emerged as a promising platform for ...CO2 extraction. Despite great achievements, existing SILMs suffer from poor structural and performance stability under high‐pressure or long‐term operations, significantly limiting their applications. Herein, a one‐step and in situ interfacial polymerization strategy is proposed to elaborate a thin, mechanically‐robust, and highly‐permeable polyamide armor on the SILMs to effectively protect ionic liquid within porous supports, allowing for intensifying the overall stability of SILMs without compromising CO2 separation performance. The armored SILMs have a profound increase of breakthrough pressure by 105% compared to conventional counterparts without armor, and display high and stable operating pressure exceeding that of most SILMs previously reported. It is further demonstrated that the armored SILMs exhibit ultrahigh ideal CO2/N2 selectivity of about 200 and excellent CO2 permeation of 78 barrers upon over 150 h operation, as opposed to the full failure of CO2 separation performance within 36 h using conventional SILMs. The design concept of armor provides a flexible and additional dimension in developing high‐performance and durable SILMs, pushing the practical application of ionic liquids in separation processes.
A thin, mechanically‐robust, and highly‐permeable polyamide armor is designed and manufactured on the supported ionic liquid membranes (SILMs) via one‐step and in situ interfacial polymerization, fundamentally resolving poor structural and performance stability of the SILMs. The armored SILMs display high operating pressure exceeding most SILMs, and ultrahigh CO2/N2 selectivity of about 200 and excellent CO2 permeation even upon over 150 h operation.
Designing nanocomposite hydrogels with oriented nanosheets has emerged as a promising toolkit to achieve preferential performances that go beyond their disordered counterparts. Although current ...fabrication strategies via electric/magnetic force fields have made remarkable achievements, they necessitate special properties of nanosheets and suffer from an inferior orientation degree of nanosheets. Herein, a facile and universal approach is discovered to elaborate MXene‐based nanocomposite hydrogels with highly oriented, heterogeneous architecture by virtue of supergravity to replace conventional force fields. The key to such architecture is to leverage bidirectional, force‐tunable attributes of supergravity containing coupled orthogonal shear and centrifugal force field for steering high‐efficient movement, pre‐orientation, and stacking of MXene nanosheets in the bottom. Such a synergetic effect allows for yielding heterogeneous nanocomposite hydrogels with a high‐orientation MXene‐rich layer (orientation degree, f = 0.83) and a polymer‐rich layer. The authors demonstrate that MXene‐based nanocomposite hydrogels leverage their high‐orientation, heterogeneous architecture to deliver an extraordinary electromagnetic interference shielding effectiveness of 55.2 dB at 12.4 GHz yet using a super‐low MXene of 0.3 wt%, surpassing most hydrogels‐based electromagnetic shielding materials. This versatile supergravity‐steered strategy can be further extended to arbitrary nanosheets including MoS2, GO, and C3N4, offering a paradigm in the development of oriented nanocomposites.
A novel supergravity‐steered approach is designed to manipulate the assembly of arbitrary nanosheets from MXene to MoS2, GO, and C3N4 for fabricating oriented nanocomposite hydrogels with heterogeneous architecture. The resultant MXene‐based nanocomposite hydrogels showcase an extraordinary electromagnetic interference shielding effectiveness (EMI SE) of 55.2 dB yet using a super‐low MXene of 0.3 wt%, surpassing most hydrogels‐based electromagnetic shielding materials.
It is particularly essential to analyze the complex crosslinked networks within polyamide membranes and their correlation with separation efficiency for the insightful tailoring of desalination ...membranes. However, using the degree of network crosslinking as a descriptor yields abnormal analytical outcomes and limited correlation with desalination performance due to imperfections in segmentation and calculation methods. Herein, we introduce a more rational parameter, denoted as harmonic amide bond density (HABD), to unravel the relationship between the crosslinked networks of polyamide membranes and their desalination performance. HABD quantifies the number of distinct amide bonds per unit mass of polyamide, based on a comprehensive segmentation of polyamide structure and consistent computational protocols derived from X-ray photoelectron spectroscopy data. Compared to its counterpart, HABD overcomes the limitations and offers a more accurate depiction of the crosslinked networks. Empirical data validate that HABD exhibits the expected correlation with the salt rejection and water permeance of reverse osmosis and nanofiltration polyamide membranes. Notably, HABD is applicable for analyzing complex crosslinked polyamide networks formed by highly functional monomers. By offering a powerful toolbox for systematic analysis of crosslinked polyamide networks, HABD facilitates the development of permselective membranes with enhanced performance in desalination applications.
Zwitterionic materials have received great attention because of the non-fouling property. As a result of the electric neutrality of zwitterionic polymers, their layer-by-layer (LBL) assembly is ...generally conducted under specific conditions, such as very low pH values or ionic strength. The formed multilayers are unstable at high pH or in a high ionic strength environment. Therefore, the formation of highly stable multilayers of zwitterionic polymers via the LBL assembly process is still challenging. Here, we report the LBL assembly of poly(sulfobetaine methacrylate) (PSBMA) with a polyphenol, tannic acid (TA), for protein-resistant surfaces. The assembly process was monitored by a quartz crystal microbalance (QCM) and variable-angle spectroscopic ellipsometry (VASE), which confirms the formation of thin multilayer films. We found that the (TA/PSBMA)n multilayers are stable over a wide pH range of 4-10 and in saline, such as 1 M NaCl or urea solution. The surface morphology and chemical composition were characterized by specular reflectance Fourier transform infrared spectroscopy (FTIR/SR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). Furthermore, (TA/PSBMA)n multilayers show high hydrophilicity, with a water contact angle lower than 15°. A QCM was used to record the dynamic protein adsorption process. Adsorption amounts of bovine serum albumin (BSA), lysozyme (Lys), and hemoglobin (Hgb) on (TA/PSBMA)20 multilayers decreased to 0.42, 52.9, and 37.9 ng/cm(2) from 328, 357, and 509 ng/cm(2) on a bare gold chip surface, respectively. In addition, the protein-resistance property depends upon the outmost layer. This work provides new insights into the LBL assembly of zwitterionic polymers.
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