Saikat Das

Topological simplification unlocks the first 4,3,3-connected tfe topology covalent organic framework, transforming high-connectivity reticular design into an unprecedented architecture for programmable wastewater purification.

Controlling electrocatalytic selectivity requires more than exposing undercoordinated metal sites; it requires placing reaction intermediates within a binding window that is strong enough for activation yet weak enough for turnover. Here we show that solvent choice can encode this balance directly into copper cluster metal–organic frameworks without changing either the copper precursor or the organic linker. Delivering 1,4‐di(4‐pyridyl)benzene in methanol or N , N ‐dimethylacetamide produces two distinct Cu(I)–thiolate frameworks, Cu ₁₀ dpb and Cu ₆ dpb, through coupled cluster growth and reticulation. Cu ₁₀ dpb contains a metal‐dense Cu ₃ –Cu ₄ –Cu ₃ node with short Cu⋯Cu contacts and heterogeneous Cu–S/Cu–O/Cu–N microenvironments, whereas Cu ₆ dpb comprises alternating Cu ₆ _ _4L and Cu ₆ _ _5L nodes built from more uniformly thiolate‐supported Cu ₆ S ₄ cages. These structural differences reshape adsorption accessibility, CO ₂ enrichment and catalytic branching. Cu ₁₀ dpb adsorbs more CO ₂ , delivers larger CO ₂ ‐dependent currents and reaches a formic‐acid Faradaic efficiency of 49.4% at −1.4 V versus RHE, with a production rate twice that of Cu ₆ dpb. In contrast, Cu ₆ dpb increasingly favours hydrogen evolution with cathodic bias. Density functional theory reveals the origin of this divergence: The higher‐coordinate Cu ₁₀ surface selectively favours HCOO* over COOH while avoiding deep adsorption wells, whereas lower‐coordinate Cu ₆ sites over‐stabilize HCOO, impede product release and bind H* more favourably. Both frameworks retain crystallinity, Cu(I) character and local cluster structure during electrolysis. These findings establish coordination‐tempered adsorption as a design principle for reticular electrocatalysts, linking solvent‐programmed cluster nuclearity to intermediate management and selective carbon conversion. More broadly, this work positions reticular chemistry as a means to programme energy landscapes by constructing, rather than merely supporting, multinuclear active sites.

The rational design of conversion‐kinetics‐promoting framework architectures offers a powerful strategy to overcome the polysulfide shuttling and sluggish conversion kinetics that limit lithium–sulfur (Li–S) batteries. Here, we report a new covalent organic framework, TUS‐44, constructed from tetrathiafulvalene‐based 4,4',4'',4'''‐([2,2'‐bi(1,3‐dithiolylidene)]‐4,4',5,5'‐tetrayl)tetraaniline and benzo[18]crown‐6‐derived 4,4′,4′′,4′′′‐(6,7,9,10,17,18,20,21‐octahydrodibenzo[ b , k ][1,4,7,10,13,16]hexaoxacyclooctadecine‐2,3,13,14‐tetrayl) tetrabenzaldehyde linkers. The resulting imine‐linked, π‐conjugated framework integrates heteroatom‐rich coordination sites within an electron‐delocalized π‐conjugated backbone, establishing a hierarchical, site‐specific interaction network (N > O > S) that governs Li ⁺ coordination, polysulfide anchoring, and dynamic charge redistribution. When coupled with conductive graphene to form an interfacial TUS‐44@G architecture, the hybrid layer functions as a chemisorptive, conversion‐kinetics‐promoting interface that regulates soluble polysulfides, facilitates interfacial charge‐transfer, and stabilizes intermediate species throughout cycling. This synergistic chemical–electronic coupling yields remarkable electrochemical performance: a high reversible capacity of 1455.7 mA h g ⁻¹ at 0.2 A g ⁻¹ , excellent rate capability of 773 mA h g ⁻¹ at 10 A g ⁻¹ , and outstanding durability with 0.034% capacity fading per cycle over 1000 cycles at 5 A g ⁻¹ . A Li–S pouch cell incorporating TUS‐44@G further delivers an outstanding initial energy density of ∼674 Wh kg ⁻¹ at 0.05 A g ⁻¹ (sulfur loading 44.558 mg), underscoring the practical potential of architecting conversion‐catalytic framework interfaces for high‐energy, durable Li–S batteries.

Breaking the long-standing permeability–selectivity trade-off remains a central challenge in membrane-based carbon dioxide separations. Here we report a heteroatom-engineering strategy that leverages structurally precise covalent organic frameworks (COFs) to transcend this limitation in mixed matrix membranes (MMMs). Two isostructural, π-conjugated two-dimensional COFs, TUS-621 and TUS-622, were rationally designed through symmetry-guided reticulation of a hexatopic triphenylene node with oxygen- and sulfur-containing diamine linkers, respectively, enabling systematic modulation of pore surface chemistry without altering topology. When incorporated into a Pebax polymer matrix, these COFs function as CO₂-philic, molecularly defined transport domains that synergistically couple preferential CO₂ sorption with ordered and fast diffusion channels. The optimized TUS-621/Pebax-10% membrane exhibits a CO₂ permeability of 433 Barrer with a CO₂/CH₄ selectivity of 55.3 under mixed-gas conditions, decisively surpassing the 2008 Robeson upper bound for CO₂/CH₄ separation while simultaneously achieving high CO₂/H₂ separation performance (CO₂ permeability of 407 Barrer and selectivity of 25.2). Comprehensive pressure- and temperature-dependent permeation studies reveal that selectivity remains remarkably stable over 2–10 bar and 25–100 °C, underscoring the robustness of the COF-enabled transport pathways. Long-term operation over 30 days shows negligible performance decay, highlighting excellent resistance to physical aging and interfacial degradation. Comparative analysis establishes that oxygen-rich pore environments in TUS-621 impart stronger CO₂ affinity and higher accessible surface area than the sulfur-containing analogue, directly translating molecular-level design into macroscopic separation performance. This work demonstrates that heteroatom-engineered COFs provide a powerful platform for overcoming fundamental transport trade-offs and advancing MMMs toward practical, high-efficiency CO₂ separations.

Cationic dyes persist in water not because they are hard to recognize, but because most adsorbents cannot engineer the right electrostatic microenvironments without sacrificing crystallinity, porosity, or recyclability. Here, we encode phenolate-rich anionic pockets into the pore walls of two π-conjugated 2D covalent organic frameworks, TU-331 and TU-332, constructed by symmetry-matched Schiff-base reticulation of 2,4-dihydroxybenzene-1,3,5-tricarbaldehyde with C₃-symmetric triamine linkers. The resulting honeycomb lattices exhibit permanent microporosity while presenting oxygen-rich, negatively polarized interfaces that preferentially bind aromatic cations. TU-331 delivers rapid and high-capacity uptake of basic green 1 and methylene blue (q_max = 302.7 and 280.0 mg g^–1), far exceeding adsorption of sulfonated azo anions. Zeta-potential and pH studies reveal electrostatic amplification of binding under basic conditions, enabling efficient regeneration with ∼99.5% capacity retention after five cycles. Importantly, TU-331 decolorizes authentic multicomponent textile dyeing effluents from a commercial facility, demonstrating function under viscosity- and additive-rich industrial matrices. Density functional theory (DFT) and symmetry-adapted perturbation theory (SAPT) analyses quantify the selectivity origin: strongly favorable binding for cationic dyes (∼−140 kcal mol^–1), dominated by Coulombic attraction and dispersion-driven π stacking, versus unfavorable association for anionic dyes. These results establish reticular microenvironment design as a blueprint for charge-selective dye capture in real wastewater.

A ladder-structured silver cluster framework stabilized by tetrazine linkers enables selective and recyclable luminescence recognition of basic amino acids in water. The background image was generated using BRIA AI.

Dimension-engineered Cu ₁₀ cluster frameworks offer robust, recyclable luminescent responses for sensitive creatinine sensing in water.

TU-82, a 3D [8 + 2]-connected bcu COF, was post-synthetically metalated to yield TU-82-M ( M = Fe, Cu). TU-82-Fe shows outstanding activity and selectivity for electrocatalytic nitrate (NO ₃ ⁻ ) reduction to ammonia via atomically dispersed Fe sites.

The rational construction of high-connectivity three-dimensional covalent organic frameworks (3D COFs) remains a central challenge in reticular chemistry, holding immense promise for advancing framework rigidity, porosity, and functional integration. From both fundamental and application standpoints, diversifying the linkage chemistry of such high-connectivity COFs beyond the archetypal imine bond is essential, as imidazole linkages impart superior chemical resilience, enhanced π-delocalization, and intrinsic polarity compared with imine linkages. Here, we report TU-123, the first 12 + 3-connected 3D imidazole-linked COF with aea topology, synthesized via a two-component cyclocondensation between a D₃-symmetric hexakis-aldehyde and a D_3h-symmetric hexaamine building block. Unlike conventional imidazole-linked COFs derived from multicomponent Debus-Radziszewski reactions, TU-123 forms through direct imidazole ring formation from aldehyde and amine precursors via an imine intermediate, intramolecular cyclization, and oxidative aromatization. This strategy, previously limited to 2D frameworks, is extended herein to a highly connected 3D network for the first time. Benefiting from its rigid and polarized imidazole framework, TU-123 exhibits a cationic surface character at neutral pH, arising from protonation of nitrogen sites within the imidazole linkages, which enables selective adsorption of anionic dyes such as acid orange 7, with a maximum adsorption capacity of 495.07 mg g^-1 and 86.08% removal efficiency under optimized conditions. The adsorption process follows pseudo-second-order kinetics and Langmuir isotherm behavior, highlighting the framework's potential for sustainable wastewater purification.