Lipeng Zhai

Three-dimensional (3D) covalent organic frameworks (COFs) are potential metal-free electrocatalysts for the oxygen reduction reaction (ORR) due to their inherent porosity and potential for fully exposed active sites. However, their practical application is severely hindered by inefficient electron transport along the extended framework and the resultant high kinetic barriers. Herein, we report a series of highly crystalline and non-interpenetrated 8-connected body-centered cubic (bcu) COFs featuring eight unstacked catalytic nodes per unit cell for ORR. By integrating redox-active azobenzene (Azo) units into the linkages, we successfully bridge the gap between electronic conductivity and catalytic activity. The incorporated Azo moieties not only narrow the bandgap but also serve as electron reservoirs, facilitating rapid electron shuttling to the imine-based active sites. Consequently, the optimal DZPy-COF achieves a remarkable half-wave potential of 0.77 V under alkaline conditions, coupled with a high turnover frequency (0.03 s–1) and enhanced capacitance (13.7 mF cm–2). Theoretical calculations reveal that the Azo units polarize the framework, lowering the energy barrier for intermediate formation, which is the rate-determining step in conventional 3D COFs. This work underscores the efficacy of leveraging high-valency topologies combined with redox-active linkages to overcome electron transport limitations in crystalline porous catalysts.

Hydrogen peroxide (H ₂ O ₂ ) is an important oxidant for chemical manufacturing, environmental remediation, and biomedical applications, yet its industrial production still relies mainly on the energy‐intensive anthraquinone process. Electrochemical H ₂ O ₂ synthesis via the two‐electron oxygen reduction reaction (2e ⁻ ORR) provides a sustainable alternative but is often hindered by sluggish charge transport and insufficient O ₂ activation. Here, we develop a bond‐hybridization strategy by incorporating sp‐hybridized acetylene units into the vertex or linker of covalent organic frameworks (COFs). The resulting COFs feature extended π‐conjugation, enhanced charge delocalization, and electronically polarized pores, thereby strengthening O ₂ adsorption and activation. Compared with sp ² ‐dominated analogues, these sp‐hybridized COFs show faster charge‐transfer kinetics, higher H ₂ O ₂ selectivity, and improved 2e ⁻ ORR activity. In a flow cell, the optimized catalyst delivers an H ₂ O ₂ production rate of 27.8 mol g ⁻¹ h ⁻¹ and a peak Faradaic efficiency of 91.7% at 150 mA cm ⁻² . Mechanistic analyses combining electronic‐structure calculations and in situ vibrational spectroscopy reveal that sp hybridization reshapes frontier‐orbital distributions and local charge density, thereby coupling framework‐wide charge delocalization with favorable O ₂ adsorption and *OOH stabilization. These results establish bond hybridization as a molecular‐level design parameter for catalytic selectivity in COFs, extending framework engineering beyond conventional functional‐group and building‐block modification.

Hydrogen peroxide (H ₂ O ₂ ) is an important oxidant for chemical manufacturing, environmental remediation, and biomedical applications, yet its industrial production still relies mainly on the energy‐intensive anthraquinone process. Electrochemical H ₂ O ₂ synthesis via the two‐electron oxygen reduction reaction (2e ⁻ ORR) provides a sustainable alternative but is often hindered by sluggish charge transport and insufficient O ₂ activation. Here, we develop a bond‐hybridization strategy by incorporating sp‐hybridized acetylene units into the vertex or linker of covalent organic frameworks (COFs). The resulting COFs feature extended π‐conjugation, enhanced charge delocalization, and electronically polarized pores, thereby strengthening O ₂ adsorption and activation. Compared with sp ² ‐dominated analogues, these sp‐hybridized COFs show faster charge‐transfer kinetics, higher H ₂ O ₂ selectivity, and improved 2e ⁻ ORR activity. In a flow cell, the optimized catalyst delivers an H ₂ O ₂ production rate of 27.8 mol g ⁻¹ h ⁻¹ and a peak Faradaic efficiency of 91.7% at 150 mA cm ⁻² . Mechanistic analyses combining electronic‐structure calculations and in situ vibrational spectroscopy reveal that sp hybridization reshapes frontier‐orbital distributions and local charge density, thereby coupling framework‐wide charge delocalization with favorable O ₂ adsorption and *OOH stabilization. These results establish bond hybridization as a molecular‐level design parameter for catalytic selectivity in COFs, extending framework engineering beyond conventional functional‐group and building‐block modification.

Unstable zinc (Zn) deposition in aqueous zinc‐ion batteries is intrinsically linked to the interfacial confinement of Zn ²⁺ transport, where ion migration is dominated by lateral diffusion along the electrode surface. This quasi‐two‐dimensional transport amplifies local electric‐field and concentration heterogeneities, leading to uneven nucleation and dendritic growth. Here, we demonstrate that Zn deposition can be fundamentally regulated by reprogramming the dimensionality of ion transport. A three‐dimensionally interpenetrated covalent organic framework (COF) incorporating crown‐ether moieties is embedded into a hydrogel electrolyte. The confined macrocyclic sites selectively coordinate Zn ²⁺ and partially displace solvating water molecules, while the interconnected crystalline channels enable continuous, isotropic bulk ion migration. This architecture converts Zn ²⁺ transport from interface‐limited diffusion to bulk‐governed three‐dimensional flux, resulting in intrinsically uniform Zn deposition. Consequently, symmetric Zn cells exhibit stable cycling for over 2000 h at 1 mA cm ⁻² , and Zn||NH ₄ V ₄ O ₁₀ full cells retain 81.6% of their capacity after 3000 cycles. These findings identify ion‐transport dimensionality as a key descriptor for metal‐deposition stability and establish a general electrolyte‐engineering strategy that transcends conventional regulation.

Unstable zinc (Zn) deposition in aqueous zinc‐ion batteries is intrinsically linked to the interfacial confinement of Zn ²⁺ transport, where ion migration is dominated by lateral diffusion along the electrode surface. This quasi‐two‐dimensional transport amplifies local electric‐field and concentration heterogeneities, leading to uneven nucleation and dendritic growth. Here, we demonstrate that Zn deposition can be fundamentally regulated by reprogramming the dimensionality of ion transport. A three‐dimensionally interpenetrated covalent organic framework (COF) incorporating crown‐ether moieties is embedded into a hydrogel electrolyte. The confined macrocyclic sites selectively coordinate Zn ²⁺ and partially displace solvating water molecules, while the interconnected crystalline channels enable continuous, isotropic bulk ion migration. This architecture converts Zn ²⁺ transport from interface‐limited diffusion to bulk‐governed three‐dimensional flux, resulting in intrinsically uniform Zn deposition. Consequently, symmetric Zn cells exhibit stable cycling for over 2000 h at 1 mA cm ⁻² , and Zn||NH ₄ V ₄ O ₁₀ full cells retain 81.6% of their capacity after 3000 cycles. These findings identify ion‐transport dimensionality as a key descriptor for metal‐deposition stability and establish a general electrolyte‐engineering strategy that transcends conventional regulation.

Developing new highly selective ion separation membranes is of great significance, but it remains a major challenge. This article reports a type of covalent organic framework (ZUT‐CEs‐COF) using crown ether organic units. ZUT‐CEs‐COF has a high specific surface area, good crystallinity, and excellent stability. The ZUT‐CEs‐COF functionalized with crown ethers structure is introduced as a nanofiller into the nanofiltration membrane separation system for ion separation. Interestingly, the thin‐film nanocomposite membrane regulated by ZUT‐CEs‐COF shows a significant increase in the selectivity coefficient for magnesium/lithium (Li ⁺ /Mg ²⁺ ) and water flux, achieving a high flux of up to 52.4 L m ⁻² h ⁻¹ , while achieving an excellent molecular screening coefficient of 26.5 for Li ⁺ /Mg ²⁺ . Density functional theory calculations further confirm that the modulation of the binding energy of ions anchored by the nanopores can provide ideas for the construction of separation membranes and promote their potential applications in the selective separation of similar ions with high selectivity.

The development of covalent organic frameworks (COFs) with robust linkages is fundamentally important for the photocatalytic production of H₂O₂. In this work, a series of isostructural COFs with robust imidazole linkage were synthesized as photocatalysts for H₂O₂ production via the precise N-substituted microenvironment regulation (benzene, pyridine, pyrimidine, and triazine). The corresponding frameworks enable water and dissolved oxygen to reach the catalytic sites easily via planar skeletons and regulation of nitrogen-atom numbers. Additionally, the N-adjustment of heterocycle units in these COFs could significantly regulate the electronic band structures, light-harvesting capacity, and hydrophilic properties. The experimental investigation demonstrated that the photocatalytic process of COFs was composed of a dominant and indirect two-electron (2e^–) oxygen reduction reaction (ORR). Notably, compared to H-COF (benzene), P-COF (pyridine), and M-COF (pyrimidine), T-COF with triazine unit exhibited the highest H₂O₂ production rate of 42180 μmol g^–1 h^–1 due to its wider visible light absorption and higher separation efficiency of photogenerated electron–hole pairs. Theoretical investigations confirmed that N-heterocycle units in COFs could precisely modulate the energy barrier related to the formation of *OOH and *O₂. This study is expected to provide a new way for rationally designing imidazole-linked COFs as promising photocatalysts for efficiently photocatalytic H₂O₂ generation.

The two novel COFs in 2D and 3D topologies were constructed for catalyzing the NO ₃ ⁻ reduction reaction, and the 3D COF showed hihger activity than 2D COFs.

Four robust imidazole-linked covalent organic frameworks with different electron effect groups (H, F, OMe and OH) were successfully constructed and OH-COF exhibits excellent ORR activity with a half-wave potential of 0.80 V ( vs. RHE).