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Transition metal oxides are efficient bifunctional catalysts for the selective catalytic reduction (SCR) of nitrogen oxides (NO x ) using CO. Nonetheless, their poor activity at lower temperatures constrains broader industrial application. Herein, we propose an optimized Fe 2 O 3 -based catalyst through strategic metal doping with Cu, Co, or Ce, which engenders a harmonious balance for the synergistic removal of CO and NO x . Among the developed catalysts, Co-doped Fe 2 O 3 , supported by rice husk ash, demonstrates superior low-temperature CO-SCR activity, achieving CO and NO x conversion ratios and N 2 selectivity above 98.5% at 100-500 °C. The enhanced catalytic performance is attributed to the catalyst's improved redox properties and acidity, engendered by strong Fe-O x -Co interactions. Furthermore, the CO-SCR reaction adheres to the Langmuir-Hinshelwood and Eley-Rideal mechanisms. Our findings shed light on the future industrial application of low-temperature CO and NO x near-zero emission technology and provide a strategy for the design of low-cost SCR catalysts., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

The crystal-facet effect of catalytic supports plays a crucial role in tailoring the physicochemical properties of active sites and the surface chemically bonded polymer can also regulate the local environment around active sites for optimizing catalytic performance. Herein, we report the effect of exposed facets of γ-Al 2 O 3 supports and further modification by surface bonded long-chain polydimethylsiloxane (PDMS) on the properties of CrO x /γ-Al 2 O 3 catalysts for selective oxidation of propene. The {111} facets of γ-Al 2 O 3 stabilize "non-redox Cr 3 + " and promote the overall oxidation rates compared with catalysts on {110} facets of γ-Al 2 O 3 . The surface bonded PDMS, with grafting density being about 0.13 chains/nm 2 , endows a hydrophobic environment to facilitate the enrichment of the hydrophobic substrate and the desorption of hydrophilic products and occupies some acid sites on catalysts to limit acid-catalyzed side reactions. The inherent liquidlike nature of bonded PDMS also forms a setting that can regulate the redox ability of surface Cr species, that lead to modified activation of oxygen toward more surface adsorbed species. As a result, the modified catalysts enhance the whole oxidation process with favorable formation of epoxide product at low reaction temperatures (<225 °C). Our findings highlight the impact of surface chemically bound polydimethylsiloxane (PDMS) upon tailoring the surroundings of the catalyst surface, and that combined with facet-effect of supports can tune the reaction process toward selective ones.

Condensation freezing inhibition is of great practical importance for anti-icing applications; however, no coatings with this performance have been reported. Here, we report the inhibition of condensation freezing on patterned polyelectrolyte coatings, including polyelectrolyte brush (PB), polyelectrolyte multilayer (PEM), and polyelectrolyte hydrogel (PH) surfaces, benefiting from their feature in regulating ice nucleation and propagation via changing counterions. On the reported surfaces, ice nucleation can be initiated exclusively at the domains with the polyelectrolytes; moreover, spontaneous ice propagation can be achieved atop the patterned polyelectrolyte surface. Consequently, condensed water surrounding the frozen drops on the patterned polyelectrolyte surface evaporates due to the instantaneously released latent heat in the course of ice propagation. Afterward, ice grows specifically on polyelectrolyte surfaces via desublimation as the saturated vapor pressure of ice is smaller than that of condensed water drops. As such, an ice-free region up to 96% of the entire surface area can be accomplished. We demonstrate that various polyelectrolyte coatings can be easily introduced on almost all surfaces, revealing great promise for anti-icing applications.

In this contribution, we report a unique co-assembly composed of pyrene and spiropyran that were linked separately at the focal point of the same peptide-based dendron (Phe-Glu), in which the dendrons offer driving forces for the coaggregation. A series of co-assemblies with different weight ratios (Py-Phe-Glu/SP-Phe-Glu) were prepared and the morphology could be tuned. It is found that the resulting stable co-assembled organogel is double switchable triggered by light and heat. TEM revealed that, in the xerogel, Py-Phe-Glu formed rigid rod nanofibers with large diameters and acted as a rigid sketelon where the gracile interwoven fibrous structure of SP-Phe-Glu grew. More interestingly, the original powder of the co-assembled xerogel (1.0 mg/0.1 mg) not only displayed a sequential high-contrast tricolored switch from dark blue to bright cyan and to red under external force but also presented multistate accessible photochromic properties. Such mechanochromic and photochromic behaviors of the xerogel are mainly due to the transition of different excimers of pyrene and the force/photoinduced ring-opening reaction of spiropyran. It is rarely reported that self-assembled soft materials achieve mechanochromic and photochromic dual-responsive behaviors with a high-contrast multicolored switch. We believe the co-assembly strategy based on polypeptide dendrons can be extended to other systems for establishing novel intelligent fluorescent materials.