Rui Liu

Achieving sustained activity without deactivation in metal oxide catalysts poses a critical challenge in volatile organic compounds abatement. Here, we introduce an entropy-increasing strategy to circumvent the inherent activity–stability trade-off by progressively incorporating thermodynamically diverse elements Zr, Mg, Co, Ni, and Mn into a CeO2 fluorite lattice to construct low-, medium-, and high-entropy oxides (LEO, MEO, and HEO). The optimized HEO affords 90% cyclohexane conversion at a markedly low 274 °C, alongside outstanding stability during both a 48 h accelerated aging test and a 100 h stability evaluation. Comprehensive analysis of fresh, used, and aged catalysts indicates that increasing configurational entropy modulates the strength of metal–oxygen bonds, precisely balancing lattice robustness and oxygen mobility, thereby sustaining a robust redox cycle. In-depth characterization under both O2-rich and O2-free conditions, combined with DFT calculations of the crystal orbital Hamiltonian population, further reveals that thermally sensitive Mn promote electron transfer for rapid oxygen activation, while thermally inert Zr strengthens metal–oxygen lattice anchoring of active elements. This synergistic enhancement enables HEO to generate the lowest ring-opening intermediates among 19 identified byproducts compared to MEO counterparts, effectively driving the deep oxidation of key intermediate benzene. This work provides a novel strategy for developing advanced non-noble metal catalysts.

Label-free quantitative detection of chemically diverse molecules is of critical importance across fields spanning medical diagnostics, food safety, and law enforcement. Surface-enhanced Raman spectroscopy (SERS) provides powerful molecular identification through fingerprint spectra, capable of achieving single-molecule detection limits when analytes are positioned directly at the plasmonic hotspots of Au/Ag substrates. Yet conventional contact-mode SERS, which relies on the direct adsorption of analytes onto bare metal surfaces, is limited by poor reproducibility and signal heterogeneity arising from random molecular orientations and competitive binding. Here, we present a proof-of-concept noncontact mode SERS platform that routinely delivers reproducible, predictable, and quantitative spectra readout, including discrimination of subtle enantiomeric differences. This platform utilizes fluorenylmethoxycarbonyl-lysine (Fmoc-Lys) scaffolds confined within 1–2 nm channels of nanoporous gold nanospheres. The Fmoc core captures target analytes through hydrophobic interactions, while the chiral center regulates the adsorption configuration/strength. This design fixes analyte distance and orientation relative to the metal surface, thereby minimizing stochastic spectral variation. We applied this platform to quantitatively analyzed methamphetamine (METH), a globally prevalent abused drug, in complex human urine samples and achieved accuracy comparable to mass spectrometry without requiring analyte-specific reference spectra. Our results highlight noncontact SERS as a general strategy for reliable, ultrasensitive molecular analysis, especially for targets lacking standard spectral libraries.

Electrochemical hydrogenation utilizing reactive hydrogen (H*) derived from water dissociation offers a sustainable route for chemical synthesis and environmental remediation. However, besides the sluggish generation of H*, its utilization efficiency, and consequently the overall electrochemical hydrogenation performance, is limited by competing hydrogen evolution and barrier interfacial H* transfer. Here, using combined theoretical and in situ spectroscopic–electrochemical analyses, we demonstrate that nitrogen vacancy (N _V )‐rich Fe ₂ N surfaces serve as highly efficient catalytic sites for generating and stabilizing H* for subsequent reactions. During water dissociation, the resulting OH species adopt a bridging μ ₂ ‐configuration between adjacent Fe atoms and undergo facile desorption, overcoming a known rate‐limiting step. Simultaneously, H* is stabilized at nitrogen sites in the form of N‐H moieties with high recombination energy barriers, creating an effective H* reservoir. This mechanism guides the application of Fe ₂ N‐N _V as a simple yet highly active catalyst for nitrate reduction, achieving over 94% Faradaic efficiency and NH ₃ selectivity. Furthermore, the accumulated H* on Fe ₂ N‐N _V enables tandem hydrogenation with cocatalysts such as cobalt ensembles (Co _n ), extending its utility to coupled electrochemical hydrogenation.

Electrochemical hydrogenation utilizing reactive hydrogen (H*) derived from water dissociation offers a sustainable route for chemical synthesis and environmental remediation. However, besides the sluggish generation of H*, its utilization efficiency, and consequently the overall electrochemical hydrogenation performance, is limited by competing hydrogen evolution and barrier interfacial H* transfer. Here, using combined theoretical and in situ spectroscopic–electrochemical analyses, we demonstrate that nitrogen vacancy (N _V )‐rich Fe ₂ N surfaces serve as highly efficient catalytic sites for generating and stabilizing H* for subsequent reactions. During water dissociation, the resulting OH species adopt a bridging μ ₂ ‐configuration between adjacent Fe atoms and undergo facile desorption, overcoming a known rate‐limiting step. Simultaneously, H* is stabilized at nitrogen sites in the form of N‐H moieties with high recombination energy barriers, creating an effective H* reservoir. This mechanism guides the application of Fe ₂ N‐N _V as a simple yet highly active catalyst for nitrate reduction, achieving over 94% Faradaic efficiency and NH ₃ selectivity. Furthermore, the accumulated H* on Fe ₂ N‐N _V enables tandem hydrogenation with cocatalysts such as cobalt ensembles (Co _n ), extending its utility to coupled electrochemical hydrogenation.

Defluorination is essential for mitigating the toxicity and persistence of fluorinated organic compounds (FOCs).

The interlayer shifting of two-dimensional (2D) covalent organic frameworks (COFs) is a critical issue affecting their sorption and catalytic properties. However, current analytical tools often measure static and averaged stacking properties from bulk samples, restricting a comprehensive understanding of the interlayer shifting process in individual 2D COFs. Here, we report real-time dynamic imaging of the solvent exchange-induced interlayer shifting in single 2D COFs using in situ dark-field optical microscopy (DFM). The increase in pore size from quasi-AB stacking to AA stacking in triphenylbenzene (TPB)-terephthaldehyde-COF and TPB-dimethoxyterephthaldehyde-COF in organic solvent and water facilitates the accommodation of more guest molecules, leading to a higher scattering intensity. By using the grayscale intensity of DFM images as a quantitative indicator, we visually observe that the solvent exchange-triggered interlayer shifting dynamics not only exhibits a significant particle-to-particle heterogeneity but also is sensitive to the solvent viscosity and interlayer interaction strength of 2D COFs. Moreover, theoretical simulations elucidate that this interlayer shifting process is governed by crystal stacking energies and follows a thermodynamically preferred pathway during the water-to-organic exchange process. This imaging methodology provides a useful way for direct observation of solvent exchange-induced interlayer shifting in single 2D COFs and understanding its dynamics.

The tunable structure of covalent organic frameworks (COFs) and their sensitivity to subtle structural modifications make them highly versatile for addressing water contamination challenges in non-homogeneous phase catalysis. However, integrating solid-liquid phase interactions and enhancing the overall efficiency of non-homogeneous catalysis remain substantial challenges. In this study, we synthesized a COF material, TPCOF-2, with an optimized pore size and strong in-plane conjugation. TPCOF-2 can efficiently remove 7 prevalent trace-level sulfonamides (SAs) from water within 30 min through a direct electron transfer pathway. Among SAs, sulfachloropyridazine (SCP) showed the fastest removal rate due to its small molecular volume, narrow HOMO-LUMO gap and high surface electrostatic potential. Degradation intermediates and pathways were characterized using high-resolution mass spectrometry. Toxicity assessments based on the ECOSAR program, alongside mineralization experiments, revealed that although certain intermediates initially exhibited higher toxicity than the parent compound, they were progressively transformed into less toxic species and eventually mineralized. These findings indicate that detoxification is achieved gradually, with a time-dependent reduction in toxicities of both the parent compound and intermediates throughout the treatment process. This study provides an efficient and sustainable strategy for removing trace amounts of complex organic pollutants from wastewater.

Adopting the essence of enzyme catalysis, the strong binding of substrates into the active site pocket for their selective activation through multiple noncovalent interactions in the reactive site design can effectively enhance the electrocatalysis process. However, mimicking the enzyme catalytic process, particularly the introduction of reactant activation mechanisms, remains a significant challenge. Herein, we present a Pd cluster inside the Fe₂N-Fe₃O₄-based built-in electric field (BEF), denoted as Pd/Fe₂N-Fe₃O₄, to serve as an enzyme mimic to activate stable C-Cl bonds. Theoretical calculations and in situ Raman indicate that the probe molecule 2,4-dichlorophenol (2,4-DCP) adsorbs onto the Pd site and rotates inside the BEF with the C₄-Cl bond being selectively activated and elongated from 1.73 to 1.82 Å. This makes Pd/Fe₂N-Fe₃O₄ an excellent electrocatalytic hydrodechlorination catalyst, with Pd usage down to 2.5 μg cm^-2, which is 32.7-360 times less than that of conventional catalysts like Pd/C, and achieving a Faradaic efficiency exceeding 20%. We reveal that besides H*-mediated electrochemical reduction, Pd/Fe₂N-Fe₃O₄ also hydrodechlorinates activated 2,4-DCP via the proton-electron coupled transfer pathway. This understanding of the role of BEF in reactant activation, along with the strategy of integrating BEF and noble metals to mimic enzymes, provides a direction for the design of advanced electrocatalysts.