Understanding the dynamic evolution of zeolite framework structures and the interactions between various hydroxyl groups or aluminum species under different steam conditions at the atomic scale is extremely crucial. Herein, using a series of characterization methods, the framework structures of HZSM-5 zeolites (Si/Al = 36) following exposure to steam in the temperature range of 100 to 500 °C are investigated. Under mild steam conditions (T ≤ 200 °C), dealumination is nearly absent, and the silanol nests directly condense to create new framework Si-O-Si bonds. Conversely, under severe steam conditions (T ≥ 300 °C), the framework tetrahedral aluminum atoms Al(IV)-1 can be sequentially converted to partially coordinated framework aluminum Al(IV)-2 and extra-framework aluminum (EFAL) through partial and complete hydrolysis, which cause an increase in the framework Si/Al ratio and a decrease in crystallinity. Al(IV)-2 is recognized as a significant intermediate species for framework complete dealumination. The Brønsted acid sites on Al(IV)-2 can be perturbed by the framework Al-OH groups due to hydrogen bonding interactions, leading to a shift in 1H chemical shifts to lower fields, appearing at 6.0-9.0 ppm and 12.0-15.0 ppm. The newly generated EFAL and silanol nests further evolve through condensation as well. Meanwhile, during dealumination, the spatial correlations (or interactions) of various hydroxyl groups on structurally distinct aluminum species [Al(IV)-1, Al(IV)-2, and EFAL] and aluminum species become extremely intricate. Based on these findings, the dynamic evolution path of HZSM-5 zeolite framework structures under mild and severe steam conditions is proposed.
In the past few years, significant efforts have been made to create and self-assemble covalent organic cages with increased complexity and functionality. However, although supramolecule cages have been widely recognized as probes to identify metal ions, the detection of mercury ions has not been fully developed. Here, we have designed and synthesized a pair of chiral cages with custom cavities based on the unique rigid structure of 1, 10-binaphthol (binol). Meanwhile, the supramolecular cage has excellent performance in high sensitivity and selectivity for detecting mercury ions. The UV titration results indicate that the binding ratio of the host to guest is 1:5. The titration curve conforms to the nonlinear fitting of the Hill function, which can obtain the binding constant K =
Enzymatic alcohol oxidation (EAO) is highly attractive thanks to its efficiency, selectivity, and sustainability benefits, but it is often neglected as a catalytic tool for practical production due to the instability and non-reusability of enzymes. Herein, a non-enantioselective alcohol dehydrogenase engineered from Candida parapsilosis (CpsADH) and a laccase from Trametes versicolor was immobilized on mesoporous silica nanoflowers (MSNs), fabricating CpsADH@MSNs (41 U/gsupport) and laccase@MSNs (67 U/gsupport) for EAO, respectively. The structural and functional properties of the MSNs endowed the immobilized enzymes with higher stability than free enzymes, and the relative activity of the immobilized enzyme was 52% and 63%, respectively, after being reused five times. The immobilized enzymes exhibited high activity, selectivity, and complementary substrate specificity in alcohol oxidation. The optimized EAO, as a versatile cascade module, was coupled with several other enzymatic transformations for multi-enzymatic synthesis of high value-added chemicals. The chiral alcohols and amines were produced with 99% ee and 84% to 98% ee, respectively, and (R)-benzoin and 2-furoic acid were prepared with 91% yield, 99% ee and 86% yield, respectively, demonstrating the synthetic utility of the immobilized enzymes.
As a naturally occurring and stable energy supply, biomass will be the leading renewable energy in the future, and its high-value application will help promote the realization of carbon neutrality. Glucose, as the basic unit of lignocellulosic biomass, has been widely investigated as the feedstock to produce various value-added chemicals. Compared to the traditional glucose valorization platforms, such as thermal catalysis and biological fermentation, solar-driven photocatalysis holds the advantages in mild reaction conditions and controllable reaction kinetics, and it is emerging as a sustainable and efficient technology for glucose conversion. With the rational design of the photocatalysts, glucose could be selectively converted into specified chemicals via oriented bond cleavage along with the sustainable generation of hydrogen at the same time, which is the so-called glucose photorefinery process. This present review introduces the general principles and latest progress in glucose photorefinery. The rational design of bifunctional photocatalysts to achieve extended light absorption, efficient charge separation, and favorable surface reaction is also introduced. The oriented breakage of the chemical bonds in glucose molecules to produce different chemicals on different active sites is highlighted. Finally, challenges and perspectives on glucose photorefinery to achieve further efficiency and more fruitful reaction pathways are proposed. This present review is believed to provide guidance for the biomass valorization by mild photocatalysis to simultaneously produce sustainable fuels and chemicals with the rational design of dually functional photocatalysts.
Radical trifunctionalization of unactivated alkenes remains rare and challenging, although they can provide a robust tool for the construction of molecules with high added value from simple materials. This work presents the relay dual N-heterocyclic carbene organocatalytic and visible-light photocatalytic multi-component trifunctionalization of alkyl alkenes via the merger of remote 1,4-cyano migration and alkylacylation. The method features a broad substrate scope and good compatibility of diverse functional groups. Density functional theory calculations were also carried out to rationalize the origin of this reaction. The cooperative N-heterocyclic carbene and photoredox catalysis enabled reductive single-electron transfer reaction of acyl azolium species and subsequent radical-radical cross-coupling, allowing for the facile construction of three new C−C bonds in one-pot reactions with high regioselectivity.
Proton exchange membrane fuel cells (PEMFCs) can be used as reactors to produce chemicals and co-generate electricity and chemicals. Their mild reaction conditions, high product selectivity, and energy utilization have profoundly impacted gas separation, water treatment, and energy utilization fields. Given the lack of systematic reports on the current research status of utilizing PEMFCs for chemical production and the co-production of electricity and chemicals, this article summarizes the types of reactions and catalyst usage involved in this multifaceted application. It analyzes how to improve the production and performance of the system from four aspects: electrolyte membranes, catalysts, assembly methods, and reaction processes. Finally, the article analyzes the current research shortcomings in utilizing PEMFCs for these applications and provides prospects for future development.
Zinc-air batteries (ZABs) belong to the category of metal-air batteries, with high theoretical energy density, safety, and low cost. Nevertheless, there are still many challenges that need to be solved for the practical application of ZABs, including high overpotential, poor cycle life, and so on. This article first briefly introduced the principle of ZABs, covering the key components, functions of each element, and challenges faced by the system. Subsequently, seven methods for studying ZABs in-situ or operando were introduced, including X-ray computed tomography (XCT), optical microscopy imaging (OMI), transmission electron microscopy (TEM), nuclear magnetic resonance imaging (MRI), X-ray diffraction (XRD), Raman spectroscopy, and X-ray absorption spectroscopy (XAS), accompanied by specific research examples. The future perspectives of ZAB characterization have also been discussed.
A “confined space” provides a unique environment to regulate the crystallization thermodynamics and kinetics by confining the reactants in the restricted space dimensions. Solid-state crystal-to-crystal transitions in confined space are controlled by the preassembly of molecules in a crystal lattice and occur inside the lattice. Herein, we report the first case of construction of crystalline cross-linked covalent organic frameworks (CL-COFs) through solid-state cross-linking of acetylenic groups-bridged 2D COFs in spatially limited systems. Specifically, this transformation is thermally induced, yielding CL-COFs with superlative properties, including outstanding enhancement in crystallinity, specific surface area, and stability. We further demonstrate the CL-COFs as high conductivity polymers after iodine doping. This work underscores the opportunity to use lattice-constrained solid-state cross-linking to develop more versatile and feature-rich polyacetylene networks.
Covalent organic frameworks (COFs) with dual linkages can combine advantages and properties of two distinct connectors, enabling the development of multifunctional materials. However, due to challenges in simultaneously forming two types of linkages, the synthesis of COFs with dual linkages remains a significant challenge. Herein, we propose a “three-in-one” molecular design strategy for synthesizing COFs with dual linkages (4-amino-4"-(2,2-dioxan-1,3-dioxan-5-yl)-[1,1':3',1"-terphenyl]-5'-yl) boronic acid (ADTB)-COF and (4'-amino-5'-(4-(2,2-dioxan-1,3-dioxan-5-yl)phenyl)-[1,1':3',1'-teroxan]-5-yl) boronic acid (ADPB)-COF through reversible condensation between three distinct functionalization groups on the monomer. Benefitting from the abundant micropores and high surface area, ADPB-COF showed excellent selective adsorption capability of C3H8 over CH4 (174, 298 K/1 bar). The present work introduces a new approach for constructing COFs with dual linkages, which greatly simplifies the synthesis process and provides a novel opportunity to develop functional materials based on COFs with multi-linkages.
The formation of C(sp3)−C(sp3) bonds has received continuous attention in organic synthesis, and the focus on versatile alkyl precursors remains constant. In our work, prevalent amines and carboxylic acids successfully serve as alkyl sources to construct C(sp3)−C(sp3) bonds via decarboxylative deamination. The catalyst-free decarboxylative alkylation reaction provides alternative access to the quaternary center. Primary mechanistic experiments suggest that it undergoes a polar mechanism.
Modulating the spectroscopic overlap between the emission bands of donors and the absorption spectra of acceptors by various simulations, it is possible to systematically investigate the emission behaviors of lanthanide complexes under different conditions. To establish the relationships between emission behaviors and various external simulations, it is necessary to study the energy transfer rate and efficiency between the donor and acceptor under different conditions to clarify the luminescent mechanism of the complexes, providing a theoretical basis for high-performance smart materials. This review focuses on the recent progress of luminescence performance of lanthanide complexes, including energy transfer mechanisms, emission color modulation, the strategies for optimizing lanthanide luminescence, and finally, various applications based on luminescence performance of lanthanide complexes and lanthanide metal-organic frameworks.
Over the last few decades, synchrotron radiation has experienced a flourishing growth, fueled by cutting-edge spectroscopic techniques that have empowered its remarkable ability to probe down to the atomic level. Indeed, this advancement has been inspiring, unlocking powerful insights and capabilities in the realm of electrochemistry community. This perspective showcases recent ground-breaking efforts and remaining challenges with respect to X-ray spectroscopy, as well as their implications for ongoing research.
Titanosilicates are widely applied in the alkene epoxidation reactions with high reaction rate and selectivity to desired products. Their catalytic performance depends on the structure topology, the micro-environment of Ti active sites, and the hydrophobicity/hydrophilicity of zeolite framework. Herein, we focus on a hydrophilic substrate of allyl alcohol (AAL) and investigated catalytic performance of four titanosilicates (TS-1, Ti-MOR,
In recent years, covalent organic frameworks (COFs) as designable crystalline porous polymers have attracted widespread attention because of their tunable structures and functionalities. In particular, the unique characteristics of COFs, such as readily controllable pore size, high surface area, editable pore surface environment, and exceptional chemical stability, provide a structural basis for loading large-sized organic, inorganic, and biological molecules for hetero-catalysis, energy storage, and other applications. In this review, we discuss state-of-the-art strategies for the structural design and synthesis, properties, and functionalities of large pore size two-dimensional and three-dimensional COFs, spotlighting recent breakthrough achievements and remarkable progress to guide further efforts in this field.
The coexistence of anions and cations in zwitterionic hydrogels results in electrostatic interactions between the polymer chains. This structure endows zwitterionic hydrogels with higher ion sensitivity and promising properties, such as anti-polyelectrolyte and thermosensitive effects. Hydrophilic groups on the molecular backbone give zwitterionic hydrogels good biocompatibility, and they effectively resist the non-specific adsorption of proteins. The abundant functional groups on the molecular skeleton also facilitate the chemical modification of zwitterionic hydrogels. In recent years, these excellent properties have made zwitterionic hydrogels broadly interesting and they have been heavily studied for medical applications. A comprehensive review will help researchers have a deeper understanding of zwitterionic hydrogels and their potential applications. In this review, the types, functional characteristics, and applications in the biomedicine of zwitterionic hydrogels are summarized in detail. In addition, the challenges and opportunities for using zwitterionic hydrogels for biomedical applications are discussed.