On-Surface Isomerization of Indigo within 1D Coordination Polymers.

Natural products are attractive components to tailor environmentally friendly advanced new materials. We present surface-confined metallosupramolecular engineering of coordination polymers using natural dyes as molecular building blocks: indigo and the related Tyrian purple. Both building blocks yield identical, well-defined coordination polymers composed of (1 dehydroindigo : 1 Fe) repeat units on two different silver single crystal surfaces. These polymers are characterized atomically by submolecular resolution scanning tunnelling microscopy, bond-resolving atomic force microscopy and X-ray photoelectron spectroscopy. On Ag(100) and on Ag(111), the trans configuration of dehydroindigo results in N,O-chelation in the polymer chains. On the more inert Ag(111) surface, the molecules additionally undergo thermally induced isomerization from the trans to the cis configuration and afford N,N- plus O,O-chelation. Density functional theory calculations confirm that the coordination polymers of the cis-isomers on Ag(111) and of the trans-isomers on Ag(100) are energetically favoured. Our results demonstrate post-synthetic linker isomerization in interfacial metal-organic nanosystems.

Overview of mechanisms of Fe-based catalysts for the selective catalytic reduction of NOx with NH3 at low temperature.

With the increasingly stringent control of NOx emissions, NH3-SCR, one of the most effective de-NOx technologies for removing NOx, has been widely employed to eliminate NOx from automobile exhaust and industrial production. Researchers have favored iron-based catalysts for their low cost, high activity, and excellent de-NOx performance. This paper takes a new perspective to review the research progress of iron-based catalysts. The influence of the chemical form of single iron-based catalysts on their performance was investigated. In the section on composite iron-based catalysts, detailed reviews were conducted on the effects of synergistic interactions between iron and other elements on catalytic performance. Regarding loaded iron-based catalysts, the catalytic performance of iron-based catalysts on different carriers was systematically examined. In the section on iron-based catalysts with novel structures, the effects of the morphology and crystallinity of nanomaterials on catalytic performance were analyzed. Additionally, the reaction mechanism and poisoning mechanism of iron-based catalysts were elucidated. In conclusion, the paper delved into the prospects and future directions of iron-based catalysts, aiming to provide ideas for the development of iron-based catalysts with better application prospects. The comprehensive review underscores the significance of iron-based catalysts in the realm of de-NOx technologies, shedding light on their diverse forms and applications. The hope is that this paper will serve as a valuable resource, guiding future endeavors in the development of advanced iron-based catalysts.