Mingyuan He

The conversion of high-density polyethylene wastes to aromatic feedstocks in noble-metal-free systems poses a significant challenge. Here, we report a steam-assisted synthesised zeolite (SA-HZSM-5) that can promote the conversion of high-density polyethylene to aromatics, achieving simultaneously high conversion and selectivity (85.4% and 49.2%, respectively) at 260 °C, outperforming noble metal-based catalysts, such as Ru-HZSM-5, under the same conditions. The produced aromatics predominantly consist of valuable monocyclic aromatics (circa 85%). The steam-assisted synthetic method endows a specific distribution of Lewis and Brønsted acid sites in SA-HZSM-5. In situ neutron diffraction and infrared spectroscopy, coupled with modelling, reveal a dual-site adsorption mechanism of mono-olefins intermediates, facilitating their transformation into dienes with suitable spaced double bonds, a feature that is crucial for the sequential cyclisation and dehydroaromatisation into aromatic compounds. This study underscores the potential of hierarchical zeolite materials for efficient upcycling of plastic wastes into chemical feedstocks.

Ethylene, one of the major basic chemicals in the modern chemical industry, has been industrially produced mainly through intensive energy-consuming steam cracking processes from light oil fractions or shale gas operated above 800 °C following the radical mechanism and seriously suffering from high methane selectivity. Herein, we report an efficient catalytic cracking reaction of 1-pentene over a tailored ZSM-5 catalyst at 700 °C with a C₂H₄/C₃H₆ ratio of 1.31 and a CH₄ selectivity below 5%, which provides an energy-saving and economically viable route for ethylene production from light oil fractions, seamlessly integrating with the existing industrial catalytic cracking processes. Mechanistic studies unveil an interesting type of zeolite catalysis different from the typical acid catalysis following the carbenium ion mechanism, termed as the confined catalytic radical (CCR) mechanism in which 1-pentene dehydrogenates to gaseous pentenyl radicals (C₅H₉•) at non-acidic [AlO₄]⁰ sites of ZSM-5 in situ formed by dehydrogenation of bridging hydroxyls, whose subsequent reactions confined in ZSM-5 produce more C₂H₄ than C₃H₆. These findings significantly broaden the concept and application of zeolite catalysis.

Copper (Cu)-based catalysts show promise for electrocatalytic CO₂ reduction (CO₂RR) to multi-carbon alcohols, but thermodynamic constraints lead to competitive hydrocarbon (e.g., ethylene) production. Achieving selective ethanol production with high Faradaic efficiency (FE) and current density is still challenging. Here we show a multivalent Cu-based catalyst, Cu-2,3,7,8-tetraaminophenazine-1,4,6,9-tetraone (Cu-TAPT) with Cu²⁺ and Cu⁺ atomic ratio of about 1:2 for CO₂RR. Cu-TAPT exhibits an ethanol FE of 54.3 ± 3% at an industrial-scale current density of 429 mA cm⁻², with the ethanol-to-ethylene ratio reaching 3.14:1. Experimental and theoretical calculations collectively unveil that the catalyst is stable during CO₂RR, resulting from suitable coordination of the Cu²⁺ and Cu⁺ with the functional groups in TAPT. Additionally, mechanism studies show that the increased ethanol selectivity originates from synergy of multivalent Cu sites, which can promote asymmetric C–C coupling and adjust the adsorption strength of different carbonaceous intermediates, favoring hydroxy-containing C₂ intermediate (*HCCHOH) formation and formation of ethanol.

The olefins industry is a cornerstone of the global chemical industry and plays a key role in the economy [ 1]. Propane dehydrogenation (PDH) is an on-purpose technology for propylene synthesis. Heterogeneous commercial catalysts containing Pt or CrOx, although widely used, are hampered by high cost, contamination or severe deactivation due to carbon deposition. Supported metal oxides have been shown to be active for C–H activation but have shown commercially unattractive performance [ 2]. Encouraged by the demands for environmental sustainability, both industry and academia are searching for environmentally friendly PDH catalysts related to the sustainable development of the olefin and chemical industries [ 3–9].

A simple photochemical route was developed that utilizes 172 nm vacuum ultraviolet (VUV) photons as driver for CO₂ hydrogenation to CO and the transformation of CH₄ to H₂ and C₂H₆.

Coordination cages have been widely reported to bind a variety of guests, which are useful for chemical separation. Although the use of cages in the solid state benefits the recycling, the flexibility, dynamicity, and metal-ligand bond reversibility of solid-state cages are poor, preventing efficient guest encapsulation. Here we report a type of coordination cage-integrated solid materials that can be swelled into gel in water. The material is prepared through incorporation of an anionic Fe^II₄L₆ cage as the counterion of a cationic poly(ionic liquid) (MOC@PIL). The immobilized cages within MOC@PILs have been found to greatly affect the swelling ability of MOC@PILs and thus the mechanical properties. Importantly, upon swelling, the uptake of water provides an ideal microenvironment within the gels for the immobilized cages to dynamically move and flex that leads to excellent solution-level guest binding performances. This concept has enabled the use of MOC@PILs as efficient adsorbents for the removal of pollutants from water and for the purification of toluene and cyclohexane. Importantly, MOC@PILs can be regenerated through a deswelling strategy along with the recycling of the extracted guests.

Upcycling of CO₂ into fuels by virtually unlimited solar energy provides an ultimate solution for addressing the substantial challenges of energy crisis and climate change. In this work, we report an efficient nanostructured Ru/MnO_x catalyst composed of well-defined Ru/MnO/Mn₃O₄ for photo-thermal catalytic CO₂ hydrogenation to CH₄, which is the result of a combination of external heating and irradiation. Remarkably, under relatively mild conditions of 200 °C, a considerable CH₄ production rate of 166.7 mmol g⁻¹ h⁻¹ was achieved with a superior selectivity of 99.5% at CO₂ conversion of 66.8%. The correlative spectroscopic and theoretical investigations suggest that the yield of CH₄ is enhanced by coordinating photon energy with thermal energy to reduce the activation energy of reaction and promote formation of key intermediate COOH* species over the catalyst. This work opens up a new strategy for CO₂ hydrogenation toward CH₄.

Nowadays, global warming is becoming more and more serious. The dramatic imagery of global warming frightens people. Carbon is situated at the core of this alarm. It has been scientifically confirmed that global warming is closely related to the increased concentration of CO₂ in the atmosphere, controlling and reducing carbon emissions has thus become a global consensus. Carbon neutrality by the mid-21st century is essential in order to limit global warming to ≤1.5°C [ 1]. This means that the atmospheric CO₂ concentration must be controlled below 450 ppm, which is also specified in the Paris Agreement and signed by 196 countries including the USA, the European Union and China. Besides, it is worth noting that China made a solemn commitment to achieve carbon peaking by 2030 and carbon neutrality by 2060 at the United Nations General Assembly in September 2020, which reflects the responsibility and determination of China to achieve this goal. Up to now, carbon neutrality has become the mainstream direction of global development transformation.