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Covalent polymerization of organic molecules into crystalline one-dimensional (1D) polymers is effective for achieving desired thermal, optical, and electrical properties, yet it remains a persistent synthetic challenge for their inherent tendency to adopt amorphous or semicrystalline phases. Here we report a strategy to synthesize crystalline 1D covalent organic frameworks (COFs) composing quasi-conjugated chains with benzoxazine linkages via the one-pot Mannich reaction. Through [4+2] and [2+2] type Mannich condensation reactions, we fabricated stoichiometric and sub-stoichiometric 1D covalent polymeric chains, respectively, using doubly and singly linked benzoxazine rings. The validity of their crystal structures has been directly visualized through state-of-the-art cryogenic low-dose electron microscopy techniques. Post-synthetic functionalizations of them with a chiral MacMillan catalyst produce crystalline organic photocatalysts that demonstrated excellent catalytic and recyclable performance in light-driven asymmetric alkylation of aldehydes, affording up to 94 % enantiomeric excess., (© 2024 Wiley-VCH GmbH.)

Tobacco, a widely cultivated crop, has been extensively utilized by humans for an extended period. However, the tobacco industry generates a significant amount of organic waste, and the effective utilization of this tobacco waste has been limited. Currently, most tobacco waste is either recycled as reconstituted tobacco sheets or disposed of in landfills. However, tobacco possesses far more potential value than just these applications. This article provides an overview of the diverse uses of tobacco waste in agriculture, medicine, chemical engineering, and energy sectors. In the realm of agriculture, tobacco waste finds primary application as fertilizers and pesticides. In medical applications, the bioactive compounds present in tobacco are fully harnessed, resulting in the production of phenols, solanesol, polysaccharides, proteins, and even alkaloids. These bioactive compounds exhibit beneficial effects on human health. Additionally, the applications of tobacco waste in chemical engineering and energy sectors are centered around the utilization of lignocellulosic compounds and certain fuels. Chemical platform compounds derived from tobacco waste, as well as selected fuel sources, play a significant role in these areas. The rational utilization of tobacco waste represents a promising prospect, particularly in the present era when sustainable development is widely advocated. Moreover, this approach holds significant importance for enhancing energy utilization., Competing Interests: Kai Shen reports financial support was provided by China Tobacco Zhejiang Industrial Co., Ltd., (© 2024 Published by Elsevier Ltd.)

Covalent organic frameworks (COFs) represent an important class of crystalline porous materials with designable structures and functions. The interconnected organic monomers, featuring pre-designed symmetries and connectivities, dictate the structures of COFs, endowing them with high thermal and chemical stability, large surface area, and tunable micropores. Furthermore, by utilizing pre-functionalization or post-synthetic functionalization strategies, COFs can acquire multifunctionalities, leading to their versatile applications in gas separation/storage, catalysis, and optoelectronic devices. Our review provides a comprehensive account of the latest advancements in the principles, methods, and techniques for structural design and determination of COFs. These cutting-edge approaches enable the rational design and precise elucidation of COF structures, addressing fundamental physicochemical challenges associated with host-guest interactions, topological transformations, network interpenetration, and defect-mediated catalysis.

There are enormous yet largely underexplored exotic phenomena and properties emerging from interfaces constructed by diverse types of components that may differ in composition, shape, or crystal structure. It remains poorly understood the unique properties a coherent interface between crystalline and amorphous materials may evoke, and there lacks a general strategy to fabricate such interfaces. It is demonstrated that by topotactic partial oxidation heterostructures composed of coherently registered crystalline and amorphous materials can be constructed. As a proof-of-concept study, heterostructures consisting of crystalline P 3 N 5 and amorphous P 3 N 5 O x can be synthesized by creating amorphous P 3 N 5 O x from crystalline P 3 N 5 without interrupting the covalent bonding across the coherent interface. The heterostructure is dictated by nanometer-sized short-range-ordered P 3 N 5 domains enclosed by amorphous P 3 N 5 O x matrix, which entails simultaneously fast charge transfer across the interface and bicomponent synergistic effect in catalysis. Such a P 3 N 5 /P 3 N 5 O x heterostructure attains an optimal adsorption energy for *OOH intermediates and exhibits superior electrocatalytic performance toward H 2 O 2 production by adopting a selectivity of 96.68% at 0.4 V RHE and a production rate of 321.5 mmol h -1 g catalyst -1 at -0.3 V RHE . The current study provides new insights into the synthetic strategy, chemical structure, and catalytic property of a sub-nanometer coherent interface formed between crystalline and amorphous materials., (© 2023 Wiley-VCH GmbH.)

Fabricating one-dimensional (1D) single-crystalline nanostructures with the necessary characteristics for interconnects and functional units in nanodevices poses a major challenge. Traditional solution-based synthesis methods, driven by oriented attachment mechanisms, have limited the growth of either ultrathin crystalline nanowires or short rod-like nanocrystals due to stringent orientation requirements. The construction of single-crystalline ultralong nanowires with both an elongated length and moderate thickness has remained elusive. Here we introduce a growth mechanism based on progressively oriented attachment that enables the attachment of larger crystals while preserving the alignment of the crystal lattice. Using this mechanism, we achieve 1D single-crystalline lanthanide-doped nanowires (K 2 YF 5 :Yb/Er) with lengths up to 9 μm and a moderate thickness of approximately 20 nm. These nanowires can be integrated into a flexible film that exhibits stretching-dependent upconverted luminescence behavior. The mechanical toughness and elongated morphology of the nanowires facilitate the development of a wearable device dedicated to multidirectional strain sensing with high responsivity and excellent stability, withstanding repeated stretching and releasing for up to 1000 cycles.

The integration of mechanically interlocked molecules (MIMs) into purely organic crystalline materials is expected to produce materials with properties that are not accessible using more classic approaches. To date, this integration has proved elusive. We present a dative boron-nitrogen bond-driven self-assembly strategy that allows for the preparation of polyrotaxane crystals. The polyrotaxane nature of the crystalline material was confirmed by both single-crystal x-ray diffraction analysis and cryogenic high-resolution low-dose transmission electron microscopy. Enhanced softness and greater elasticity are seen for the polyrotaxane crystals than for nonrotaxane polymer controls. This finding is rationalized in terms of the synergetic microscopic motion of the rotaxane subunits. The present work thus highlights the benefits of integrating MIMs into crystalline materials.

The structural diversity of three-dimensional (3D) covalent organic frameworks (COFs) are limited as there are only a few choices of building units with multiple symmetrically distributed connection sites. To date, 4 and 6-connected stereoscopic nodes with T d , D 3h , D 3d and C 3 symmetries have been mostly reported, delivering limited 3D topologies. We propose an efficient approach to expand the 3D COF repertoire by introducing a high-valency quadrangular prism (D 4h ) stereoscopic node with a connectivity of eight, based on which two isoreticular 3D imine-linked COFs can be created. Low-dose electron microscopy allows the direct visualization of their 2-fold interpenetrated bcu networks. These 3D COFs are endowed with unique pore architectures and strong molecular binding sites, and exhibit excellent performance in separating C 2 H 2 /CO 2 and C 2 H 2 /CH 4 gas pairs. The introduction of high-valency stereoscopic nodes would lead to an outburst of new topologies for 3D COFs., (© 2022 Wiley-VCH GmbH.)

Direct observation of the surface-enhanced Raman scattering (SERS) of molecules adsorbed on nano-sized zirconia (ZrO 2 ) substrates was first reported without the need for the addition of metal particles. It was found that ZrO 2 nanoparticles can exhibit unprecedented Raman signal enhancements on the order of 10 3 for the probe molecule 4-mercaptobenzoic acid (4-MBA). The dramatic effect of the calcination temperature on the ZrO 2 nanoparticles was also investigated. The ZrO 2 nanoparticles with the particle diameter of 10.5 nm, which were prepared by calcination at a temperature of 500°C, have the highest SERS activity. A comparison between the experimental and calculation results indicates that charge transfer (CT) effects dominate the surface enhancement. The plentiful surface state of ZrO 2 active substrate that is beneficial to CT resonance occurs between molecules and ZrO 2 to produce a SERS effect. The CT process depends, to a large extent, on the intrinsic properties of the modifying molecules and the surface properties of the ZrO 2 . This is a new SERS phenomenon for ZrO 2 that will expand the application of ZrO 2 to microanalysis and is beneficial for studying the basic properties of both ZrO 2 and SERS.