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The pursuit of sustainable practices through the chemical recycling of polyamide wastes holds significant potential, particularly in enabling the recovery of a range of nitrogen‐containing compounds. Herein, we report a novel strategy to upcycle polyamide wastes to tertiary amines with the assistance of H2 in acetic acid under mild conditions (e.g., 180 °C), which is achieved over anatase TiO2 supported Mo single atoms and Rh nanoparticles. In this protocol, the polyamide is first converted into diacetamide intermediates via acidolysis, which are subsequently hydrogenated into corresponding carboxylic acid monomers and tertiary amines in 100 % selectivity. It is verified that Mo single atoms and Rh nanoparticles work together to activate both amide bonds of the diacetamide intermediate, and synergistically catalyze its hydrodeoxygenation to form tertiary amine, but this catalyst is ineffective for hydrogenation of carboxylic acid. This work presents an effective way to reconstruct various polyamide wastes into tertiary amines and carboxylic acids, which may have promising application potential. [ABSTRACT FROM AUTHOR]

Upcycling biodegradable polyester waste into value-added chemicals can not only avoid CO2 emissions but also achieve sustainable carbon recycling. Herein, we report a one-pot catalytic process to deconstruct polycaprolactone into 6-aminocaproic acid (EACA) and caprolactam (CPL), two monomers of nylon-6, using aqueous ammonia and Ru catalysts. No additional hydrogen is required, and the total yield of EACA and CPL could reach 90.2% using a ternary catalyst, Ru/CeO2/RGO, at 140 °C. It is verified that 6-hydroxyhexanoic acid and 6-hydroxyhexanoamide are the initial intermediates resulting from polycaprolactone decomposition, which undergo dehydrogenation, amination and re-hydrogenation to transform into EACA and 6-aminohexanoamide over the Ru catalyst. The hydrolysis of 6-aminohexanoamide produces EACA, and the reverse reaction between dehydration of EACA and hydrolysis of CPL results in their coexistence. The protocol demonstrated here provides a novel route to recycle polycaprolactone to valuable chemicals. [ABSTRACT FROM AUTHOR]

Production of fuel and chemicals from plastic waste is one of the effective ways to upcycle spent plastics, which is an interesting topic and of significance for green and sustainable development. Herein, we demonstrate a highly efficient catalyst, TiO2 nanoparticle supported Ru nanocatalyst (Ru/TiO2), for upcycling polyethylene terephthalate (PET) to alkanes in the presence of H2 and water. Under the optimal conditions (200 °C, 60 bar H2, and small amount of H2O), PET could completely convert into alkanes, dominated with cyclohexane and methane. It was indicated that the strong interaction between the TiO2 support and Ru nanoparticles made electrons flow from the TiO2 support to the Ru nanoparticles, which thus rendered Ru/TiO2 to have ability to simultaneously catalyze PET hydrolysis and intermediate hydrogenation. This work realizes the transformation of PET to alkanes, which provides a promising way to chemically upcycle PET. [ABSTRACT FROM AUTHOR]

The CO2 hydrogenation to free formic acid is an interesting topic, and low‐cost and high‐performance catalysts are highly desirable. This work presents a simple and green strategy to prepare high‐performance Ru catalysts for CO2 hydrogenation using cellulose and phytic acid composite (CPC) as support to complex with Ru(III). The CPC support prepared with assistance of 1‐butyl‐3‐methyl imidazolium chloride exhibits porous structure with abundant free −OH and −PO4 groups that can complex with Ru(III). The CPC complexed Ru catalyst (e. g., CPC‐Ru‐1) showed much higher activity for CO2 hydrogenation to formic acid in 1‐butyl‐3‐methyl imidazolium acetate than the reported heterogeneous Ru catalysts. Especially, CPC‐Ru‐1 with 0.094 wt% Ru afforded formic acid in selectivity >99 % with a turnover number around 1.8×104 and an initial production rate of 15.21 mol ⋅ g−1 ⋅ h−1 within the first 2 h at 120 °C. This catalyst is recyclable and stable without obvious activity loss after 5 runs. [ABSTRACT FROM AUTHOR]

Herein, we report a CO2-mediated base catalysis approach for the activation of triple bonds in ionic liquids (ILs) with anions that can chemically capture CO2 (e.g., azolate, phenolate, and acetate), which can achieve hydration of triple bonds to carbonyl chemicals. It is discovered that the anion-complexed CO2 could abstract one proton from proton resources (e.g., IL cation) and transfer it to the C≡N or C≡C bonds via a six-membered ring transition state, thus realizing their hydration. In particular, tetrabutylphosphonium 2-hydroxypyridine shows high efficiency for hydration of nitriles and C≡C bond-containing compounds under a CO2 atmosphere, affording a series of carbonyl compounds in excellent yields. This catalytic protocol is simple, green, and highly efficient and opens a new way to access carbonyl compounds via triple bond hydration under mild and metal-free conditions. [ABSTRACT FROM AUTHOR]

N-Methylation of amines with CO2/H2 to N-methylamines over non-noble metal catalysts is very interesting but remains challenging. Herein, we present an alcohol (e.g., ethanol) promoted strategy for the N-methylation of anilines with CO2/H2 with high efficiency under mild conditions (e.g., 125 °C), which is achieved over a cobalt catalytic system composed of Co(OAc)2·4H2O, triphos and Sn(OTf)2. This catalytic system has a broad substrate scope and is tolerant toward a wide range of anilines and N-methyl anilines, and a series of N,N-dimethyl anilines were obtained in high yields. Mechanism investigation indicates that the alcohol solvent shifts the equilibrium of CO2 hydrogenation by forming an alkyl formate, which further reacts with the amine to produce N-formamide, and Sn(OTf)2 promotes the deoxygenative hydrogenation of N-formamides to afford N-methylamines. This is the first example of the N-methylation of amines with CO2/H2 over a cobalt catalytic system, which shows comparable performance to the reported Ru catalysts and may have promising applications. [ABSTRACT FROM AUTHOR]

The photocatalytic transformation of carbon dioxide (CO 2 ) into valuable chemicals is a challenging process that requires effective and selective catalysts. However, most polymer-based photocatalysts with electron donor-acceptor (D-A) structures are synthesized with a fixed D-A ratio by using expensive monomers. Herein, we report a simple strategy to prepare polyarene oxides (PAOs) with quinone structural units via oxidation treatment of polyarene (PA). The resultant PAOs show tunable D-A structures and electronic band positions depending on the degree of oxidation, which can catalyze the photoreduction of CO 2 with water under visible light irradiation, generating CO as the sole carbonaceous product without H 2 generation. Especially, the PAO with an oxygen content of 17.6% afforded the highest CO production rate of 161.9 μmol g -1 h -1 . It is verified that the redox transformation between quinone and phenolic hydroxyl in PAOs achieves CO 2 photoreduction coupled with water oxidation. This study provides a facile way to access conjugated polymers with a tunable D-A structure and demonstrates that the resultant PAOs are promising photocatalysts for CO 2 reduction.