Article-Journal

Abstract Achieving robust room-temperature ferromagnetism in purely organic 2D crystals remains a fundamental challenge, primarily due to antiferromagnetic (AFM) coupling mediated by {\pi}-electron superexchange. Here, we present a mix-topology design strategy to induce strong ferromagnetic (FM) coupling in metal-free 2D systems. By covalently connecting radical polyaromatic hydrocarbon monomers (also referred to as nanographenes) with distinct sublattice topologies, this approach rationally breaks inversion symmetry and enables selective alignment of majority spins across the extended network, giving rise to metal-free ferromagnetism. Based on this strategy, we designed a family of 32 organic 2D crystals featuring spin-1/2 and mixed spin-1/2-spin-1 honeycomb lattices. Systematic first-principles calculations reveal that these materials are robust FM semiconductors with tunable spin-dependent bandgaps ranging from 0.9 to 3.8 eV. Notably, we demonstrate record-high magnetic coupling of up to 127 meV, spin-splitting energies exceeding 2 eV, and Curie temperatures surpassing 550 K, indicating thermal stability well above room temperature. The microscopic origin of the strong FM exchange stems from enhanced spin-orbital overlap and dominant direct exchange, while AFM superexchange is effectively suppressed. Our findings establish a generalizable design principle for realizing robust metal-free FM semiconductors and open new avenues for developing flexible and biocompatible magnets for next-generation spintronic and quantum technologies.

Nov 18, 2025

Abstract Two-dimensional (2D) covalent organic frameworks (COFs), as stacked 2D polymers, have emerged as promising semiconductors with tunable structures and functionalities, offering significant potential in optoelectronics. Achieving in-plane anisotropy in their electronic and optical properties is particularly desirable for applications in electronics, thermoelectrics, and photonics but remains a considerable challenge with existing design and synthesis approaches. Here, we present a novel design strategy to introduce intralayer anisotropy in 2D conjugated COFs (2D aniso-c-COFs) using nodes with large in-plane quadrupole moment imbalances and identical linkers. By rationally designing twelve 2D aniso-c-COFs based on benzodithiophene (BDT) nodes, we impose a highly anisotropic electronic structure that results in unprecedented bidirectional charge transport, where electrons and holes preferentially migrate along divergent directions. These COFs exhibit remarkable charge mobilities, reaching up to 1200 cm2V− 1s− 1 for electrons and 200 cm2V− 1s− 1 for holes, as predicted by Boltzmann transport theory. Parallel to electronic anisotropy, these materials show pronounced optical anisotropy, including giant birefringence (|Δn| > 1.0) and linear dichroism (|Δk| > 1.3), which are unprecedented in COFs, enabling selective polarization control and tunable optical responses. Guided by these insights, we synthesized a representative 2D aniso-c-COF, TBDT-P-CN, and experimentally demonstrated its high intrinsic charge mobility. These results establish anisotropic 2D conjugated COFs as a unique platform for bidirectional charge transport and polarization-sensitive optoelectronic applications, paving the way for future advancements in organic crystalline materials.

Oct 18, 2025

Abstract Porphyrin and phthalocyanine-based covalent organic frameworks (COFs) have emerged as versatile scaffolds for developing high-performance photo- and electrocatalysts. By enabling precise anchoring of metal species onto their cores, these COFs allow for meticulous tuning of chemical and electronic properties, facilitating single-atom distribution and achieving outstanding catalytic performance. However, the majority of these COFs are restricted to two-dimensional (2D) architectures, where the catalytic activity of the metal centers is often compromised due to eclipsed stacking layers, limiting their optimization potential. To address this challenge, we report the synthesis of three-dimensional (3D) porphyrin and phthalocyanine-based COFs with a cyt topology. This innovative structural arrangement facilitates the atomic-level distribution of distinct metal species across steric exposed networks, and the synergistic effect of bimetallic sites leads to exceptional electrocatalytic activity in urea oxidation reactions with a current density of 10 mA cm−2 at just 1.37 VRHE. This study not only broadens the topological diversity of 3D COFs but also establishes a platform for achieving uniform and accessible multimetal distributions, paving the way for synergistic electrocatalytic materials.

Aug 18, 2025

Abstract Covalent organic frameworks promise inexpensive, low-toxic, and lightweight thermoelectrics for energy harvesting and temperature control. Nevertheless, systematic materials development has been hitherto impeded by a poor understanding on the relationships among performance, microscopic transport processes, and chemical structures. Here, by using a multi-scale first-principles computational scheme hybridizing the model-driven and data-driven learning approaches, an integrated framework describing their lattice and charge-carrier dynamics is established, and thus advance the existing knowledge of synthesis and performance to the atomistic-level understanding. It is unveiled that continuous tunable thermoelectric figure of merits of covalent organic frameworks can be achieved through the atomic-scale chemical modifications, in which not only the high mobility but also the low lattice thermal conductivity lies at the heart of their decent thermoelectric efficiency. It is corroborated that the enhanced interlayer electronic couplings by substituting with relatively heavier elements minimizes the negative impacts caused by the inherent stacking disorder. Such a strategy concomitantly gives rise to the more low-frequency optical phonons and the softened acoustic modes, markedly strengthening the vibrational anharmonicity and suppressing the thermal transport. It is anticipated that our new insights lay the groundwork for designing new thermoelectric covalent organic frameworks with higher performance.

Aug 17, 2025

Abstract As an emerging class of porous aromatic polymers, porphyrin-based covalent organic frameworks (COFs) have been widely employed in assorted applications due to their unique electronic configurations and properties. Notably, three-dimensional (3D) COFs, characterized by porphyrin cores exposed along steric ordered nanochannels, exhibit great promise for solar energy conversion. However, the development of 3D porphyrin-based COFs continues to present a synthetic challenge, stemming from the scarcity of appropriate topotactic designs and appropriate building blocks. In this study, a series of 3D Por-An-COFs with a reasonable 2-fold lvt-b topology have been synthesized. The 3D architecture enables the periodic alignment of porphyrin units within the conjugated backbones, facilitating light harvesting and interactions between guest species and active centers. Consequently, the 3D Por-An-COF features superior photoresponsive characteristics, including high solar-to-chemical and solar-to-thermal conversion capabilities. In particular, the interfacial water evaporation system based on 3D Por-An-COF achieved an evaporation rate of 1.64 kg m–2 h–1, and the related thermoelectric device generates an output voltage of 195 mV. This research not only extends the structural diversity of 3D porphyrin-based COFs for photoenergy conversion but also elucidates the intrinsic dimensionality-dependent photoresponsive behaviors, providing valuable insights for the development of advanced porphyrin-based photosensitizers for a wide range of applications.

Aug 11, 2025

Abstract Employing organic semiconductors to drive photocatalytic processes for chemical fuel production and pollutant degradation is a viable pathway for tackling the energy crisis and environmental pollution. In this review, we summarize the development of organic semiconductor photocatalysis so far and propose the future vision of organic semiconductors as state-of-the-art photocatalysts in practical applications. Compared to inorganic semiconductors, organic semiconductors display a large absorption coefficient and easily tunable topological and electronic structures, which set them apart from ordinary inorganic photocatalysts. However, the chemical instability, high exciton dissociation energy and low charge carrier mobility of organic semiconductors are the major obstacles to the improvement of their photocatalytic activity. Obviously, the opportunity and challenge coexist in the development of organic semiconductor photocatalysis. In light of this, we systematically compare the merits and shortcomings of organic semiconductors for heterogeneous photocatalysis and enumerate some feasible approaches to overcoming the bottlenecks hindering their photocatalytic performance. By carefully considering factors such as conjugated linkage types, building blocks, and electron donor-acceptor structures, highly reactive and stable organic semiconductor photocatalysts can be developed.

Jun 17, 2025

Abstract The emerging laser writing represents an efficient and promising strategy for covalent two dimensional (2D)-patterning of graphene yet remains a challenging task due to the lack of applicable reagents. Here, we report a versatile approach for covalent laser patterning of graphene using a family of trivalent organic iodine compounds as effective reagents, allowing for the engraving of a library of functionalities onto the graphene surface. The relatively weak iodine-centered bonds within these compounds can readily undergo laser-induced cleavage to in situ generate radicals localized to the irradiated regions for graphene binding, thus completing the covalent 2D-structuring of this 2D-film. The tailor-made attachment of distinct functional moieties with varying electrical properties as well as their thermally reversible binding manner enables programming the surface properties of graphene. With this delicate strategy the bottleneck of a limited scope of functional groups patterned onto the graphene surface upon laser writing is tackled.

Oct 14, 2024

We predicted, for the first time, the emergence of Stoner-ferromagnetic half-metals, as well as antiferromagnetic Mott-Hubbard insulators in metal-free 2D polymers.

Oct 2, 2024

We predicted, for the first time, the emergence of Stoner-ferromagnetic half-metals, as well as antiferromagnetic Mott-Hubbard insulators in metal-free 2D polymers.

Oct 2, 2024

Abstract Introducing continuous mesochannels into covalent organic frameworks (COFs) to increase the accessibility of their inner active sites has remained a major challenge. Here, we report the synthesis of COFs with an ordered bicontinuous mesostructure, via a block copolymer self-assembly-guided nanocasting strategy. Three different mesostructured COFs are synthesized, including two covalent triazine frameworks and one vinylene-linked COF. The new materials are endowed with a hierarchical meso/microporous architecture, in which the mesochannels exhibit an ordered shifted double diamond (SDD) topology. The hierarchically porous structure can enable efficient hole-electron separation and smooth mass transport to the deep internal of the COFs and consequently high accessibility of their active catalytic sites. Benefiting from this hierarchical structure, these COFs exhibit excellent performance in visible-light-driven catalytic NO removal with a high conversion percentage of up to 51.4 %, placing them one of the top reported NO-elimination photocatalysts. This study represents the first case of introducing a bicontinuous structure into COFs, which opens a new avenue for the synthesis of hierarchically porous COFs and for increasing the utilization degree of their internal active sites.

Feb 14, 2024