ACS Catalysis 最新文献

Amino aldehyde intermediates exhibit extreme chemical lability, undergoing nonproductive cyclization and polymerization in bulk solvent at rates orders of magnitude faster than enzymatic recapture. This kinetic mismatch has posed a fundamental bottleneck for transaminase-mediated stepwise diamination. Here, we resolve this long-standing challenge by discovering a previously unrecognized trans-subunit tunnel within a homodimeric transaminase that directly channels the unstable amino aldehyde intermediate between the two pyridoxal-5′-phosphate (PLP) active sites, bypassing release and rebinding. Mechanism-guided semi-rational engineering of the trans-subunit tunnel in Shimia marina transaminase (SMTA) yielded the S122G/Y324N with 1.98-fold enhanced catalytic efficiency (k_cat/K_M) for the stepwise diamination of 2,5-diformylfuran (DFF) to bis(aminomethyl)furan (BAMF). Stopped-flow kinetics and molecular dynamics simulations revealed that the mutations shift the tunnel from a tight-binding locked state to a dynamic-transport regime, reducing steric hindrance and optimizing electrostatic guidance to accelerate inter-subunit intermediate transit. A whole-cell cascade converting renewable 5-hydroxymethylfurfural (5-HMF) to BAMF—a promising bio-based diamine for advanced polyamides—was subjected to techno-economic (TEA) and life cycle (LCA) analyses. Together, these findings establish tunnel engineering as a generalizable paradigm for sequential biocatalytic amination. This work provides a mechanism-driven blueprint for efficient transaminase-mediated stepwise diamination, enabling biocatalytic production of bio-based diamines from renewable feedstocks.

Electrochemical nitrate reduction (NO₃RR) offers a promising route for the production of valuable fertilizers and nitrites (common food preservatives), yet the relevant active sites remain poorly defined. Here, we combine density functional theory (DFT) with operando electrochemical scanning tunneling microscopy (n-EC-STM) to analyze tunneling current noise and establish structure–activity relationships in Ag/Au(111) and Ag/Au(100) model systems. DFT calculations show that Ag overlayers strengthen nitrate adsorption relative to bare Au and facilitate the initial NO₃* → NO₂* step. The adsorption energetics depend on both the structure of the surface facet and adsorption geometry, with tridentate nitrate adsorption generally favored on Au(100)-based surfaces and more variable behavior on Au(111)-based surfaces. Experimentally, Ag-coated Au(111) and Au(100) exhibit strong coverage-dependent NO₃RR activity, with maximum activity near completion of an Ag monolayer on both facets. Ag_ML/Au(100) consistently outperforms Ag_ML/Au(111). n-EC-STM identifies Ag(100)-like monolayer terraces as the dominant active sites for NO₃RR, whereas adjacent Au sites remain inactive. The same design principle is reproduced in Au{100} nanocubes, where Ag_5nm@Au_43nm/C with a thinner Ag shell outperforms Ag_11nm@Au_43nm/C and Au_43nm/C. Together, these results identify terrace-confined Ag monolayers on Au as the key active sites for the electrochemical nitrate reduction reaction and highlight the roles of strain, ligand presence, and electronic effects at the Ag/Au–electrolyte interface.

The discovery of high-performance ethylene polymerization catalysts remains challenging because catalytic behavior is governed by a complex interplay between ligand structure, conformational flexibility, and reaction conditions. Herein, we present a data-driven framework for catalyst discovery that integrates semiempirical descriptor engineering, interpretable machine learning, and DFT analysis. Using an automated workflow based on SMILES-derived structures, conformer sampling, and xTB/RDKit descriptors, chemically meaningful representations were constructed for a diverse set of Co- and Fe-based bis(imino)pyridyl catalysts. The resulting structure-condition models accurately predict catalytic activity, achieving an R² of 0.86 with the optimized XGBoost model. Interpretable analysis establishes a local angular descriptor associated with the N-aryl substituent geometry as an important structural factor governing catalytic activity, which is further supported by DFT calculations. Guided by these insights, systematic ligand design establishes practical rules favoring reduced proximal steric congestion and electronically tunable ortho substituents, enabling the identification of promising Fe/Co catalyst candidates. This framework provides a general strategy for accelerating the rational discovery and design of homogeneous polymerization catalysts.

Metal phthalocyanine (MPc)-based catalysts offer a structurally tunable platform for the oxygen reduction reaction (ORR) in alkaline media, yet their application in anion-exchange membrane fuel cells (AEMFCs) has been limited by insufficient performance. Here, we report two iron tetra-azaphthalocyanine catalysts, AZ-FT-30 and AZ-FO-30, evaluated in AEMFCs. Both catalysts exhibit comparable electrochemical surface areas (∼156–158 m² g^–1), enabling isolation of intrinsic activity. AZ-FO-30 demonstrates better catalyst activity toward alkaline ORR and enhanced cathode performance, achieving a peak power density of 902 mW cm^–2 under H₂–O₂ conditions, representing the highest reported value for MPc-based AEMFC cathodes to date. Notably, the AZ-FO-30-based cell sustains stable operation over 35 h at 400 mA cm^–2 with a minimal voltage decay (2.4 mV h^–1), demonstrating the capability of MPc systems to achieve extended device-level durability. Density functional theory calculations demonstrate that AZ-FO-30 exhibits the shortest Fe–O bond distance, indicative of the strongest OH adsorption at the Fe active site, a trend consistently observed with the model containing one explicit water molecule, confirming its good adsorption characteristics. These findings demonstrate that targeted modification of the phthalocyanine framework enables the development of high-performance and durable cathode materials for platinum-group metal-free AEMFCs.

Here, we report a dual photoredox/cobalt catalytic system for synthesis of α-chlorocarbonyls through Kharasch-type addition and cotelomerization using readily available alkyl radical precursors, Michael acceptors, and collidine hydrogen chloride salts. This catalysis enables simultaneous installation of alkyl and chloride groups across Michael acceptors via alkyl radical addition to Michael acceptors followed by cobalt chloride-mediated halogen atom transfer to the α-carbonyl radicals. Notably, this platform tolerates various patterns of alkyl radical generation, such as single-electron reduction of redox active esters or an oxalate, and metal hydride-mediated hydrogen atom transfer to alkenes. These features enable rapid and programmable synthesis of α-chlorocarbonyl compounds from readily available materials.