Chem & Bio Engineering最新文献

Lignin, characterized by its amorphous, heavily polymerized structure, is a primary natural source of aromatic compounds, yet its complex constitution poses considerable challenges in its transformation and utilization. Therefore, the selective cleavage of C–C bonds represents a critical and challenging step in lignin degradation, essential for the production of high-value aromatic compounds. In this study, we report a simple electrocatalytic approach for lignin valorization via C–C bond cleavage by developing a nonmetallic electrocatalyst of carbon-based materials. It is found that the hydrophilicity and hydrophobicity of the electrocatalyst have a significant effect on the degradation process. Under mild conditions, the hydrophilic carbon paper exhibits 100% substrate conversion, yielding 97% benzaldehyde and 96% quinone with ionic liquid electrolytes. The mechanism study shows that the carbon catalyst with higher surface defects favors electron transfer in the oxidative cleavage process of C–C bonds. These results signify a substantial advancement in lignin degradation, offering an environmentally friendly, metal-free electrochemical route.

Metallic structures with hierarchical open pores that span several orders of magnitude are ideal candidates for various catalyst applications. However, porous metal materials prepared using alloy/dealloy methods still struggle to achieve continuous pore distribution across a broad size range. Herein, we report a printable copper (Cu)/iron (Fe) composite ink that produces a hierarchical porous Cu material with pores spanning over 4 orders of magnitude. The manufacturing process involves four steps: 3D-printing, annealing, dealloying, and reannealing. Because of the unique annealing process, the resulting hierarchical pore surface becomes coated with a layer of Cu–Fe alloy. This feature imparts remarkable catalytic ability and versatile functionality within fixed bed reactors for 4-nitrophenol (4-NP) reduction and Friedländer cyclization. Specifically, for 4-NP reduction, the porous Cu catalyst demonstrates an excellent reaction rate constant (k_app = 86.5 × 10^–3 s^–1) and a wide adaptability of the substrate (up to 1.26 mM), whilst for Friedländer cyclization, a conversion over 95% within a retention time of only 20 min can be achieved by metal–organic-framework-decorated porous Cu catalyst. The utilization of dual metallic particles as printable inks offers valuable insights for fabricating hierarchical porous metallic structures for applications, such as advanced fixed-bed catalysts.

Water plays a significant role in CO₂ hydrogenation, which is capable of accelerating the reaction in an autocatalytic manner, but the reason for water promotion in the system is still controversial. This work dissects the mechanisms behind the autocatalytic behavior of water in CO₂ hydrogenation. Based on the stable structure of CuZn(211) alloy under the reaction condition, density functional theory is employed to systematically explore all possible autocatalytic modes of water. We find that the influence of water on the reaction is mainly reflected in O–H bonding, in which water tends to facilitate the O–H bond formation by a direct participator mechanism. The nature of the facilitating effect is attributed to the nucleophilic property of O–H bonding. Due to the involvement of water, the reaction activity is enhanced with the improvement of CO selectivity. This work can provide a paradigm for investigating the origin of the autocatalytic behavior of water in heterogeneous catalysis.

Conventional room temperature phosphorescence (RTP) polymer materials lack a dynamic structural change mechanism for on-demand phosphorescence emission, limiting their application in specific scenarios, such as smart devices. However, the development of RTP polymer materials with an on-demand emission capability is highly attractive yet rather challenging. Herein, we report a novel RTP polymer material that doped purely organic chromophores into a polymer network with numerous free hydroxyl side chains. This unique polymer material can be 3D printed with RTP activated through thermal-triggered nonequilibrium transesterification, where on-demand phosphorescence emission is achieved because of the increased cross-linking degrees such that the thermal motion of chromophores is effectively restricted. As a result, ultralong RTP emission is successfully observed due to enhanced stiffness in the polymer network. Importantly, the modulus changes of the polymer during nonequilibrium transesterification are intuitively visualized based on the intensity of phosphorescence emission. Through liquid crystal display (LCD) 3D printing, complex shaped and multimaterial structured objects are demonstrated, targeting the information encryption of printed objects and on-demand regional emission of multicolored phosphorescence. This study would provide an avenue to control RTP with on-demand emission and contributes to the field of anticounterfeiting and detection applications for intelligent RTP materials.

Technetium-99 (⁹⁹Tc), predominantly present as pertechnetate (⁹⁹TcO₄^–), is a challenging contaminant in nuclear waste from artificial nuclear fission. The selective removal of ⁹⁹TcO₄^– from nuclear waste and contaminated groundwater is complex due to (i) the acidic and intricate nature of high-level liquid wastes; (ii) the highly alkaline environment in low-activity level tank wastes, such as those at Hanford, and in high-level wastes at locations like Savannah River; and (iii) the potential for ⁹⁹TcO₄^– to leak into groundwater, risking severe water pollution due to its high mobility. This Review focuses on recent developments in advanced porous materials, including metal–organic frameworks (MOFs), covalent organic frameworks (COFs), and their amorphous counterparts, porous organic polymers (POPs). These materials have demonstrated exceptional effectiveness in adsorbing ⁹⁹TcO₄^– and similar oxyanions. We comprehensively review the adsorption mechanisms of these anions with the adsorbents, employing macroscopic batch/column experiments, microscopic spectroscopic analyses, and theoretical calculations. In conclusion, we present our perspectives on potential future research directions, aiming to overcome current challenges and explore new opportunities in this area. Our goal is to encourage further research into the development of advanced porous materials for efficient ⁹⁹TcO₄^– management.

Self-supported branched poly(ethylenimine) scaffolds with ordered macropores are synthesized with and without Al₂O₃ powder additive by cross-linking poly(ethylenimine) (PEI) with poly(ethylene glycol) diglycidyl ether (PEGDGE) at −196 °C. The scaffolds’ CO₂ uptake performance is compared with a conventional sorbent, i.e., PEI impregnated on an Al₂O₃ support. PEI scaffolds with Al₂O₃ additive show narrow pore size distribution and thinner pore walls than alumina-free materials, facilitating higher CO₂ uptake at conditions relevant to direct air capture. The PEI scaffold containing 6.5 wt % Al₂O₃ had the highest CO₂ uptake of 1.23 mmol/g of sorbent under 50% RH 400 ppm of CO₂ conditions. In situ DRIFT spectroscopy and temperature-programmed desorption experiments show a significant CO₂ uptake contribution via physisorption as well as carbamic acid formation, with lower CO₂ binding energies in PEI scaffolds relative to conventional PEI sorbents, likely a result of a lower population of primary amines due to the amine cross-linking reactions during scaffold synthesis. The PEI scaffold containing 6.5 wt % Al₂O₃ is estimated to have the lowest desorption energy penalty under humid conditions, 4.6 GJ/t_CO2, among the sorbents studied.

Using solid adsorbents for the destructive sorption of nitrogen trifluoride (NF₃) presents a potential solution to its dual challenges as a potent greenhouse gas and hazardous compound in microelectronics. In this study, a series of MOFs (M-MOF-74, M = Mg, Co, Ni, Zn) with open metal sites (OMSs) are utilized for NF₃ adsorption. By employing single-component adsorption isotherms and the ideal adsorbed solution theory (IAST) selectivity calculations, the adsorption performance of various adsorbents is evaluated. The results indicate that Mg, Co, and Ni-MOF-74 exhibit high adsorption capacities for NF₃, while Zn-MOF-74 shows a lower adsorption capacity, likely due to the weaker Lewis acidity of Zn²⁺. Experimental findings from PXRD and gas adsorption studies indicate structural pore alteration in the MOF-74 series following NF₃ gas adsorption. Theoretical computational analyses reveal that the MOF-74 series has a higher adsorption affinity for NF₃ compared to N₂. This research provides insights into the use of efficient MOF sorbents for the destructive adsorption of NF₃.

Adsorptive separation employing porous materials is one of the most promising alternative technologies for C₂H₂ purification due to its energy-efficient and environmentally friendly advantages. Herein, we present the design and synthesis of a dicopper-paddle-wheel-based metal–organic framework (termed JNU-5-Me) with a carboxylate-azolate organic linker. The use of such a linker results in the axial positions of the dicopper paddle wheels being occupied by azolates, and therefore, a much-improved chemical stability of the framework structure. JNU-5-Me shows negligible adsorption of C₂H₄, C₂H₆, and CO₂ at 1.0 bar and 298 K, while a gate-opening effect for C₂H₂ and a large C₂H₂ adsorption (4.7 mmol g^–1) at 1.0 bar and 298 K. Dynamic breakthrough studies on JNU-5-Me demonstrate its excellent C₂H₂ separation performance from C₂H₂/CO₂ (50/50, v/v) and C₂H₂/CO₂/C₂H₄/C₂H₆ (70/10/10/10, v/v/v/v) mixtures. Additionally, in-situ infrared spectroscopy and Grand canonical Monte Carlo (GCMC) simulation reveal that the carboxylate oxygens and methyl groups on the framework are involved in the strong binding of C₂H₂, which may be attributed to the gate-opening effect of JNU-5-Me.

Zeolite P1, a significant conversion product of fly ash, is predominantly utilized for the removal of metal ions, adsorption of carbon dioxide, and capture of aromatic compounds. Despite its diverse applications, its role as a catalyst remains underexplored in the scientific community. Traditionally, mordenite (MOR) zeolites are considered typical dimethyl ether (DME) carbonylation catalysts, whose Brønsted acid sites located on the 8-membered rings (8-MR) are the key active sites for this reaction. This conventional approach underscores the importance of specific zeolite structures in facilitating catalytic processes. H–P1 zeolite was synthesized through a template-free approach in this paper. When applied to DME carbonylation, this zeolite exhibited an impressive selectivity of up to 93% for methyl acetate (MA), suggesting its potential as a highly effective catalyst. This promising outcome hints at a new frontier for the application of the P1 zeolite, potentially revolutionizing its role in catalysis and expanding its utility beyond traditional adsorption processes. The findings suggest that the P1 zeolite could be a versatile material in the realm of catalytic chemistry, offering new pathways and methodologies for various chemical reactions.