Xiaoping Tan

Rational modulation of charge polarization in covalent organic frameworks constitutes a fundamental strategy for optimizing photocatalytic performance, yet achieving precise and systematic control over these parameters remains a significant challenge. Moreover, the interplay in covalent organic frameworks between molecular dipole moments, electronic structure, and catalytic activity is poorly understood. Here, we demonstrate that controlled extension of the acceptor unit in donor–acceptor (D–A) type covalent organic frameworks (COFs) provides an effective handle for tuning charge polarization. By systematically elongating the acceptor linker from phenylene to naphthalene and anthracene, we achieve progressive modulation of the molecular dipole moment, accompanied by narrowed bandgaps and suppressed charge recombination, as confirmed by combined spectroscopic and density functional theory analyses. When evaluated in the photocatalytic oxidation of tetrahydroisoquinolines, the anthracene-linked Aa-COF delivers near-quantitative product yield (98%) under mild conditions, with scalability demonstrated via gram-scale synthesis and solar-driven operation. Mechanistic studies implicate superoxide and singlet oxygen as the primary reactive species, while Fukui analysis identifies enhanced nucleophilicity as a key factor facilitating oxygen activation. This work establishes acceptor extension as a viable design principle for polarization-modulated COF photocatalysts, offering a generalizable approach for selective organic transformations under sustainable conditions.

The performance of urea-formaldehyde (UF) resin and its formaldehyde emission is a natural contradiction. High molar ratio UF resin performance is very good, but its formaldehyde release is high; low molar ratio UF resin formaldehyde release is reduced, but the resin itself performance becomes very bad. In order to solve this traditional problem, an excellent strategy of UF resin modified by hyperbranched polyurea is proposed. In this work, hyperbranched polyurea (UPA_6N) is first synthesized by a simple method without any solvent. UPA_6N is then added into industrial UF resin in different proportions as additives to manufacture particleboard and test its related properties. UF resin with a low molar ratio has a crystalline lamellar structure, and UF-UPA_6N resin has an amorphous structure and rough surface. The results show that internal bonding strength increased by 58.5%, modulus of rupture increased by 24.4%, 24 h thickness swelling rate (%) decreased by 54.4%, and formaldehyde emission decreased by 34.6% compared with the unmodified UF particleboard. This may be ascribed to the polycondensation between UF and UPA_6N, while UF-UPA_6N resin forms more dense three-dimensional network structures. Finally, the application of UF-UPA_6N resin adhesives to bond particleboard significantly improves the adhesive strength and water resistance and reduces formaldehyde emission, suggesting that the adhesive can be used as a green and eco-friendly adhesive resource for the wood industry.

Covalent organic frameworks (COFs), as a novel platform for the synthesis of metal nanoparticles, display abundant properties of adjustable porosity, high crystallinity and large surface area. In particular, three-dimensional (3D)-COFs are unique skeletons with greater surface areas, numerous easily accessible active sites and interpenetrating channels compared to 2D-COFs. These eminent properties of 3D-COFs are very beneficial for anchoring metal nanoparticles, and effectively restrict the size and growth of nanoparticles, enhancing the catalytic performance. In this study, we prepare hybrid nano-materials (denoted as AgNPs-3D-COF) based on Ag nanoparticles and a hydroxy functional 3D-COF. The strong coordination between OH groups and metal Ag and finite aperture generate uniform and small size Ag nanoparticles. When applied to the catalytic reduction of 4-nitrophenol and the degradation of organic dyes, namely methylene blue and Congo red, AgNPs-3D-COF delivers high activity and enduring cycling stability. We expect that this study can offer a strategy for constructing advanced heterogeneous metal nanoparticle catalysts and accelerate the advancements of 3D-COFs.

In this paper, the host–guest recognition and sensing between macrocyclic pillar[6]arene (CP6) and sodium cyclamate (SC) is first researched. A fluorescent sensing platform is fabricated with CP6 modified reduced graphene (CP6-RGO) as the receptor and the probe rhodamine B (RB), which shows high selectivity and sensitivity for the detection of SC. The structure of the CP6-RGO nano-material is confirmed by transmission electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared and thermogravimetric analysis. The mechanism of host–guest recognition between CP6 and SC is also investigated by ¹H NMR. As a consequence, highly selective, fast and sensitive fluorescence sensing is developed, which has a linear response range of 0.1–50.0 μM and a low detection limit of 0.075 μM (S/N = 3) for SC. This method is also used to detect SC in carbonate beverage practical samples. This strategy might have potential applications for the determination of the abuse of food additives and provide a way to guard serious food security issues.

Gold nanoparticles (Au NPs) are installed in situ on the surfaces of graphitic carbon nitride (g-C₃N₄) based on supramolecular hydroxylatopillar[6]arene (P6). The Au NPs can be obtained via the redox reaction between HAuCl₄ and P6 without any NH₂-NH₂, NaBH₄, and other reductants, where AuCl₄ ^- is reduced to Au⁰ by the -OH groups in the presence of OH^-, and the -OH groups are oxidized into -COOH. First, P6 is loaded onto the surface of g-C₃N₄ via π-π interaction between P6 and g-C₃N₄, which offers a stabilized and reduced site for in situ anchoring of Au NPs. The hybrid nanomaterial Au-NPs@P6@g-C₃N₄ exhibits higher catalytic capability than the Pd/C catalyst in 4-nitrophenol (4-NP) reduction and methylene blue degradation, which opens a new avenue for designing more efficient hybrid nanomaterials for application in catalysis, sensing, and other fields.