Kyriakos C. Stylianou

Achieving sustainable carbon capture under realistic, humid conditions remains a central challenge for decarbonization technologies. Here we report an ultramicroporous oxofluorovanadate metal‐organic framework, Ni(pyrazine) ₂ (VOF ₄ ), that dynamically regulates competitive adsorption through reversible redox chemistry. Under humid dilute CO ₂ streams (4 vol%), water chemisorbs at vanadium centers in the form of hydroxide ligands and induces a reversible V(+4)|V(+5) transformation to an isoreticular phase, Ni(pyrazine) ₂ (VO(OH)F ₄ ), while CO ₂ is engaged in strong physisorption within pyrazine‐lined pore regions. This redox‐driven compartmentalization of H ₂ O and CO ₂ results in a dynamic breakthrough CO ₂ capacity of 2.04 ± 0.07 mmol/g, sustained for up to 50 cycles and showing resilience under intense humidification or steam exposure. These findings establish redox‐adaptive adsorption in BVR‐X as a unique design paradigm, enabling scalable and durable carbon capture under realistic operating conditions.

Achieving sustainable carbon capture under realistic, humid conditions remains a central challenge for decarbonization technologies. Here we report an ultramicroporous oxofluorovanadate metal‐organic framework, Ni(pyrazine) ₂ (VOF ₄ ), that dynamically regulates competitive adsorption through reversible redox chemistry. Under humid dilute CO ₂ streams (4 vol%), water chemisorbs at vanadium centers in the form of hydroxide ligands and induces a reversible V(+4)|V(+5) transformation to an isoreticular phase, Ni(pyrazine) ₂ (VO(OH)F ₄ ), while CO ₂ is engaged in strong physisorption within pyrazine‐lined pore regions. This redox‐driven compartmentalization of H ₂ O and CO ₂ results in a dynamic breakthrough CO ₂ capacity of 2.04 ± 0.07 mmol/g, sustained for up to 50 cycles and showing resilience under intense humidification or steam exposure. These findings establish redox‐adaptive adsorption in BVR‐X as a unique design paradigm, enabling scalable and durable carbon capture under realistic operating conditions.

Increasing the energy density of Li‐ion batteries requires cathodes that can store more than one electron per transition‐metal center. Iron‐based conversion cathodes such as FeF ₃ are attractive due to their high theoretical capacity and low cost; however, their practical performance is limited by large voltage hysteresis, sluggish kinetics, and capacity loss during cycling. Here, we report a ball‐milled FeF ₃ /FePO ₄ composite cathode that combines the high capacity of FeF ₃ with the superior reversibility of FePO ₄ . Compared to pure FeF ₃ , the composite retains high capacity while exhibiting improved rate capability, lower polarization, and markedly enhanced cycling stability. After prelithiation, the composite delivers a reversible discharge capacity of 572 mAh g ⁻¹ , corresponding to a specific energy of 1175 Wh kg ⁻¹ . These results show that integration of FeF ₃ and FePO ₄ offers an effective route to cathodes that combine high capacity with high reversibility.

Increasing the energy density of Li‐ion batteries requires cathodes that can store more than one electron per transition‐metal center. Iron‐based conversion cathodes such as FeF ₃ are attractive due to their high theoretical capacity and low cost; however, their practical performance is limited by large voltage hysteresis, sluggish kinetics, and capacity loss during cycling. Here, we report a ball‐milled FeF ₃ /FePO ₄ composite cathode that combines the high capacity of FeF ₃ with the superior reversibility of FePO ₄ . Compared to pure FeF ₃ , the composite retains high capacity while exhibiting improved rate capability, lower polarization, and markedly enhanced cycling stability. After prelithiation, the composite delivers a reversible discharge capacity of 572 mAh g ⁻¹ , corresponding to a specific energy of 1175 Wh kg ⁻¹ . These results show that integration of FeF ₃ and FePO ₄ offers an effective route to cathodes that combine high capacity with high reversibility.

Metal-organic frameworks (MOFs) offer a structurally tunable platform for photocatalysis, yet their activity for hydrogen evolution is often constrained by inefficient charge separation and reliance on metal cocatalysts. Herein, a family of MOFs, BVR-19-M, constructed from divalent transition metal ions (M = Mg2+, Mn2+, Cu2+, Zn2+, Cd2+) and the aliphatic amino acid l-cystine is reported. Among them, BVR-19-Zn exhibits the highest photocatalytic activity, enabled by the zinc’s filled d-orbitals and the redox-active disulfide l-cystine ligand, promoting intraligand charge transfer (ILCT). Uniquely, the disulfide (S–S) bridges within BVR-19-Zn undergo transient homolytic cleavage upon light irradiation, generating a thiyl radical and thiolate anion pair that actively mediate charge separation and drive hydrogen evolution in the absence of a co-catalyst. Open-shell metal ions incorporated into BVR-19-M either introduce a mid-gap state that serves as a recombination center or promote metal-centric charge transfer, both of which diminish photocatalytic efficiency. The radical anion-mediated ILCT mechanism introduces a distinct molecular design strategy for MOFs, demonstrating how disulfide redox chemistry can be harnessed to unlock efficient, sustainable photocatalysis.

Low-concentration ammonia detection is critical for applications in environmental monitoring, agricultural production, and occupational health protection. To enhance the material's gas-detection capability, a nanocomposite of a MOF and a conducting polymer was synthesized via in situ polymerization and systematically optimized for chemiresistive ammonia sensing. By varying the UiO-66 loading, the trade-off between gas-accessible surface area and electrical conductivity was established. A contactless spray-deposition technique was developed to fabricate composite films on compact interdigitated electrode platforms, overcoming the limitations of conventional drop-casting methods in film uniformity and device reproducibility. The optimized 5 wt % UiO-66/PANI sensor demonstrated exceptional performance, with 138% sensitivity at 100 ppb ammonia, representing nearly a three-fold improvement over pristine PANI (48% at 100 ppb). The sensor exhibited excellent selectivity toward ammonia over common interfering gases, robust stability across varying humidity conditions, and consistent performance over long-term cyclic testing. An open-space demonstration in a laboratory environment validated the sensor's real-time ammonia-monitoring capability, with performance comparable to that of a commercial ammonia sensor. This work provides a systematic approach to optimizing MOF/conducting polymer composites for gas-sensing applications via a reliable selected-area deposition method. The results demonstrate the potential of UiO-66/PANI nanocomposites as a practical platform for ammonia detection in environmental and industrial settings.

Light-driven isotopic labeling is currently dominated by homogeneous catalysis and largely relies on separate thiol-based hydrogen-atom-transfer catalysts. Metal–organic frameworks (MOFs), with their modular structures, confined pore environments, and tunable optoelectronic properties, offer an attractive but largely unexplored heterogeneous platform for controlled isotopic incorporation in chemicals. Herein, we report a systematic investigation of MOF-photocatalyzed hydrogen/deuterium (H/D) exchange, demonstrating that UiO-66-type materials uniquely enable thiol-free, formyl-selective deuteration of aromatic aldehydes using D2O as the sole deuterium source. Under UV irradiation, UiO-66 materials achieve up to 97% H/D incorporation over 3 h with 99% product selectivity, a level of control far surpassing that of catalyst-free photochemistry. Evaluation of the influence of linker functionalization shows that efficiency depends on multiple interdependent parameters, including radical generation, porosity, substrate binding and diffusion, and D2O accessibility, thereby establishing it as a key design handle for controlling reactivity in H/D exchange. Mechanistic investigations using electron paramagnetic resonance spectroscopy, controls using isotopically enriched UiO-66 and zirconium oxo clusters, and density functional theory analysis demonstrate that the Zr6O4(OH)4 nodes actively participate in catalysis, enabling deuterium transfer via proton-coupled electron-transfer mechanisms involving in situ-generated μ3-OD groups. Aldehyde confinement at the Zr6-cluster surface suppresses competing oxidation pathways and promotes a surface-confined radical mechanism that is inaccessible to homogeneous photocatalysts. Our findings establish UiO-66 as a single-component heterogeneous photocatalyst for selective isotopic labeling and mechanistically probe a previously unexplored mode of node-centered photoreactivity in MOFs. This work provides mechanistic insights into the use of MOFs for isotopic labeling and late-stage functionalization under mild conditions, highlighting the role of node-centered photochemistry.

Mitigating rising atmospheric CO2 levels remains one of the most pressing global challenges. Among emerging solutions, solid adsorbent technologies offer efficient, reusable, and economically viable routes for CO2 capture. Here, we contribute to this field by introducing a crystal-engineering strategy for zeolitic imidazolate framework-8 (ZIF-8), a robust and scalable metal–organic framework (MOF) synthesized under green, room-temperature conditions. Controlled wet chemical etching generates surface and bulk defects and exposes new crystal faces, increasing the number of coordinatively unsaturated Zn sites available for spermine grafting. This dual modification leads to an 84-fold enhancement in CO2 uptake at 40 mbar compared to pristine ZIF-8. Breakthrough experiments (4 vol % CO2 balanced with N2) under both dry and humid conditions confirm selective and stable CO2 capture, retaining ∼90% of uptake even at 75% relative humidity. In situ 13CO2 solid-state NMR provides direct molecular-level evidence of carbamate formation, confirming chemisorption interactions. Our findings demonstrate that wet chemical etching coupled with amine grafting is an attractive strategy for modulating bulk and surface reactivity in MOFs, unlocking previously inaccessible Zn sites and enabling high-performance, humidity-tolerant CO2 capture under industrially relevant conditions.