Arne Thomas

The electrocatalytic nitrate reduction reaction (NO ₃ RR) enables sustainable nitrate remediation and simultaneous ammonia synthesis as an alternative to the energy‐intensive Haber‐Bosch process. Recently, covalent organic frameworks (COFs) have garnered attention as NO ₃ RR platform due to their intrinsic porosity and structural tunability, which enable active‐site engineering. However, current COF‐based systems largely rely on metal active sites, undermining their sustainability and obscuring the catalytic activity of the framework. Here, we introduce a metal‐free COF, that is highly active for NO ₃ RR. The electrocatalyst is a fluorinated ketazine‐linked COF (F‐Ketazine COF), which incorporates electron‐withdrawing fluorine atoms that enhance π–π stacking interactions and promote efficient linkage formation. Synthesized via a rapid solvothermal reaction, the F‐Ketazine COF exhibits superior crystallinity and enhanced electrocatalytic activity compared to its non‐fluorinated analog (n‐Ketazine COF). Under neutral pH conditions, the F‐Ketazine COF achieved a Faradaic efficiency of 59.9% for NH ₃ and an NH ₃ yield rate of 1639.9 µmol h ⁻¹ mg _COF ⁻¹ at −0.9 V versus RHE. To the best of our knowledge, this is the first example of a ketazine‐linked COF applied in electrocatalysis and the first a metal‐free COF for NO ₃ RR. This work demonstrates the potential of fluorinated ketazine linkages in developing sustainable and efficient COF‐based electrocatalysts.

The electrocatalytic nitrate reduction reaction (NO ₃ RR) enables sustainable nitrate remediation and simultaneous ammonia synthesis as an alternative to the energy‐intensive Haber‐Bosch process. Recently, covalent organic frameworks (COFs) have garnered attention as NO ₃ RR platform due to their intrinsic porosity and structural tunability, which enable active‐site engineering. However, current COF‐based systems largely rely on metal active sites, undermining their sustainability and obscuring the catalytic activity of the framework. Here, we introduce a metal‐free COF, that is highly active for NO ₃ RR. The electrocatalyst is a fluorinated ketazine‐linked COF (F‐Ketazine COF), which incorporates electron‐withdrawing fluorine atoms that enhance π–π stacking interactions and promote efficient linkage formation. Synthesized via a rapid solvothermal reaction, the F‐Ketazine COF exhibits superior crystallinity and enhanced electrocatalytic activity compared to its non‐fluorinated analog (n‐Ketazine COF). Under neutral pH conditions, the F‐Ketazine COF achieved a Faradaic efficiency of 59.9% for NH ₃ and an NH ₃ yield rate of 1639.9 µmol h ⁻¹ mg _COF ⁻¹ at −0.9 V versus RHE. To the best of our knowledge, this is the first example of a ketazine‐linked COF applied in electrocatalysis and the first a metal‐free COF for NO ₃ RR. This work demonstrates the potential of fluorinated ketazine linkages in developing sustainable and efficient COF‐based electrocatalysts.

The rapid in situ encapsulation of a [NiFe]-hydrogenase into covalent organic frameworks (COFs) enables noble metal-free photocatalytic hydrogen evolution and hydrogen oxidation reactions.

Covalent organic frameworks (COFs) exhibit significant potential for gas separation applications, primarily due to their remarkable stability and precisely adjustable pore structures. However, creating sustainable COF-based gas separation membranes remains unachieved and is confronted with significant challenges, including high defect sensitivity, poor recyclability, high-cost and poor pressure resistance. To address these challenges, a molecular knitting strategy is applied for reconstructing long-range ordered COF nanosheets (CONs) into super-robust and nearly defect-free COF membranes using tris(2-aminoethyl)amine (TREN) as the suture. Notably, the disassembly and self-assembly of designated CONs into membranes can be achieved through thermodynamic control by solvent switching in the presence of TREN. The underlying mechanism of this thermodynamically driven molecular structure transformation is elucidated using density functional theory calculations. The COF membranes derived from dynamically knitted CONs exhibit excellent self-healing and recycling capabilities and superior ideal selectivity for gas separation. It demonstrates an ultrahigh Young’s modulus of 19.68 GPa, corresponding to an approximate 992-fold enhancement over that of original COF membranes (0.021 GPa). Ultimately, the fabricated COF membranes exhibit outstanding pressure-resistant (ΔP > 6 bar), anti-plasticizing and H₂/CO₂ selectivity (113 ~ 52), largely surpassing the Robeson upper bound.

Constitutional isomerism in covalent organic frameworks (COFs) has shown promise for enhancing material properties, especially for photocatalytic applications. Herein, we design two isomeric multicomponent COFs (MC-COFs) via Schiff-base condensation followed by a Povarov reaction to convert the imine linkages into quinoline structures. These isomeric MC-COFs possess opposing C=N bond orientations and differently aligned phenyl groups within COF pores, leading to distinct torsion angles in COF layers. Structural analysis reveals that the enhanced planarity of COFs promotes π-π stacking and electron delocalization, resulting in a favorable band structure and reduced exciton binding energy. Consequently, the COFs achieve a superior hydrogen peroxide (H ₂ O ₂ ) production rate of 3128 µmol g ⁻¹ h ⁻¹ under visible light. This study underscores the critical influence of structural isomerism on the photocatalytic efficiency of MC-COFs and provides insights for optimizing COF-based photocatalytic systems.

This review discusses the electrochemical lignin valorization, including depolymerization to vanillin, benzoic acid, and quinones through oxidation and upgrading via hydrogenation/hydrogenolysis to produce value-added chemicals.

Covalent organic frameworks (COFs) are promising photocatalysts for hydrogen peroxide (H ₂ O ₂ ) production, yet their rational design remains challenging. Although machine learning has advanced the prediction of properties of porous materials, its application to COF-based photocatalysis faces two major challenges: the representation of multilevel structural features and the limited availability of training datasets. Here we present a comprehensive computational framework, termed ‘information co-evolution’, that accelerates the discovery of efficient COF structures for H ₂ O ₂ photosynthesis. This framework integrates two pathways: to mitigate data limitations, we introduce data augmentation techniques and ensemble modelling; concurrently, to address the structural encoding challenge, we introduce a cross-level feature fusion strategy that integrates these fragment descriptors with mechanism-driven physical descriptors. These strategies collectively reduced the validation root mean square error from 4.70 to 3.31. Among over 10,000 candidates, our framework can successfully identify high-performance COFs for H ₂ O ₂ photosynthesis, for example, COF-343 achieves a H ₂ O ₂ photosynthetic rate of 12,978.7 μmol h ⁻¹ g ⁻¹ . The model interpretation further unveiled critical structural motifs, offering information for the rational design of COF photocatalysts beyond traditional trial-and-error methods.

The development of robust heterogeneous photocatalysts capable of operating under harsh chemical conditions remains a critical yet challenging goal in materials science. Here, we present a postcyclization strategy based on conjugation lock-in reinforcement to construct sulfur-heteropolycyclic covalent organic frameworks (COFs) with asymmetric electron distribution for superior photocatalytic reactions, which is achieved through a consecutive thionation–cyclization–oxidation transformation of N-acylhydrazone precursors using Lawesson’s reagent. Systematic characterization reveals that sulfur incorporation endows the framework with enhanced chemical stability, localized asymmetric electron density, rapid charge carrier migration, efficient exciton dissociation, extended π-conjugation, and a well-defined donor–acceptor architecture, collectively leading to significantly improved photocatalytic activity and durability compared to the original hydrazone-linked COF. Consequently, the modified COF exhibits a H₂O₂ evolution rate of 5270 μmol g^–1 h^–1 in pure water, representing a 3-fold enhancement over the precursor COF (1878 μmol g^–1 h^–1) and surpassing most reported organic and inorganic competitors. Moreover, it achieves complete conversion of benzylamine within 1 h under mild blue light-emitting diode irradiation, demonstrating high efficiency in aerobic oxidation catalysis. These findings establish the lock-in reinforcement strategy coupled with electronic structure modulation as a versatile route to designing durable and highly active photocatalysts for demanding synthetic and energy-conversion applications.

Cu ₂ O nanocubes coated with porous covalent organic framework (COF) layers enable efficient and selective electrochemical CO ₂ reduction to C ₂₊ products. The Cu@COF core–shell catalysts show high activity, good current density and enhanced stability.

A –COOH-functionalized COF synthesized via the multicomponent Doebner reaction shows high proton conductivity from room to elevated temperatures. Dangling –COOH groups form H-bonded water networks, enabling Grotthuss proton hopping without dopants.