@article {48708, title = {Metal-catalyzed plastic depolymerization}, journal = {Cell Reports Physical Science}, volume = {4}, year = {2023}, month = {MAY}, pages = {101341}, type = {Review}, abstract = {

Polymers have become an indispensable part of our daily lives, and today we produce around 370 MT of plastic per year. Only about 20\% of it is being recycled, and the rest, 80\%, is unleashed into the environment without appropriate treatment. This calls forth the evaluation of strategies available for mitigating the menace of {\textquoteleft}{\textquoteleft}after-use{\textquoteright}{\textquoteright}plastic waste. Various approaches have evolved over a decade and are at different levels of development. Plastic depolymerization and upcycling are considered some of the most prominent and long-term solutions. The metal-catalyzed depolymerization of plastic waste to chemical feedstocks has emerged as one of the promising ways to address global plastic pollution. Therefore, this review aims to examine the available metal-catalyzed depolymerization methods, notify recent progress, pinpoint current gaps, and gauge the potential of this strategy. Both homogeneous and heterogeneous catalysts have been reported to depolymerize various polymers over the last decade. Considerable advances have been reported in the metal-mediated depolymerization of polyolefins, polyesters, polycarbonates, polyurethanes, polyamides, and polyethers. The depolymerization of the above polymers produces the monomers or intermediates, which can be used again for polymerization and thus brings the waste polymers back into circularity. The overview debates the usage of high temperaagents, etc., in metal-catalyzed depolymerization. Thus, this review summarizes the current understanding of the fundamental science of metal-catalyzed plastic depolymerization, the remaining scientific challenges, and the potential opportunities.

}, doi = {10.1016/j.xcrp.2023.101341}, author = {Khopade, Kishor V. and Chikkali, Samir H. and Barsu, Nagaraju} } @article {49292, title = {Copper/Iron cocatalyzed depolymerization of postconsumer polycarbonate: a one-pot strategy to synthesize aryl ethers}, journal = {ACS SUSTAINABLE CHEMISTRY \& ENGINEERING}, volume = {12}, year = {2024}, month = {DEC 7}, pages = {18362-18372}, type = {Journal Article}, keywords = {aryl ethers, copper/iron cocatalysis, depolymerization, polycarbonates, Value-added products}, issn = {2168-0485}, doi = {10.1021/acssuschemeng.4c06990}, author = {Moyilla, Nageswararao and Padhi, Ganeshdev and Kalsi, Deepti and Barsu, Nagaraju} } @article {49291, title = {Depolymerization of waste polyethylene to linear alkenes via sequential dehydrogenation and metathesis}, journal = {Green Chemistry}, volume = {26}, year = {2024}, month = {OCT}, pages = {10558-10566}, type = {Article}, abstract = {

Polyethylene (PE) is the most abundantly sourced plastic and significant efforts are needed for its end-of-life management. The deconstruction of PE is an uphill task and requires the breaking of highly stable C-C bonds. Here we demonstrate that PE can be deconstructed to value-added dodecene, along with other long-chain alkenes. The PCP-iridium complex catalyzes the dehydrogenation of commercial and post-consumer polyethylene waste to produce dehydrogenated polyethylene (DHP) with 0.5-1.0\% unsaturation. The DHP was subjected to an ethylene cross-metathesis reaction in the presence of suitable catalysts. Through meticulous optimization of reaction parameters, 63\% selectivity toward dodecene, with 26\% overall yield, was achieved. The practical significance of our method has been demonstrated by subjecting post-consumer plastic waste to dehydrogenation followed by ethylene metathesis to produce dodecene as a major product, together with long-chain alkenes. The PE deconstruction has been confirmed by recording molar mass before and after depolymerization using high-temperature gel permeation chromatography. The existence of dodecene has been unambiguously ascertained using GC, GC-MS, NMR, and IR spectroscopy. Thus, these results demonstrate the conversion of waste PE to value-added dodecene and long-chain alkenes under mild reaction conditions.

}, issn = {1463-9262}, doi = {10.1039/d4gc03646h}, author = {Khopade, Kishor V. and Rajput, Nikhita S. and Rangappa, Raghavendrakumar and Barsu, Nagaraju and Chikkali, Samir H.} } @article {49307, title = {Base-mediated denitrative C3-alkylation of quinoxaline derivatives}, journal = {Organic \& Biomolecular Chemistry}, volume = {23}, year = {2025}, month = {JAN }, pages = {303-307}, type = {Article}, abstract = {

We have developed a novel base-mediated method for the selective C3-alkylation of quinoxalin-2(1H)-one and N-protected quinoxalin-2(1H)-one using inexpensive, unactivated nitroalkanes. This approach tolerates a wide range of functional groups and supports the synthesis of various bioactive compounds. Gram-scale reactions demonstrate the scalability of the method. The proposed mechanism was validated by control experiments.

}, issn = {1477-0520}, doi = {10.1039/d4ob01571a}, author = {Pansare, Vaibhav Ramachandra and Barsu, Nagaraju} } @article {49421, title = {Depolymerization of waste polycarbonates to value-added products}, journal = {ChemSusChem}, volume = {18}, year = {2025}, month = {JAN}, type = {Article}, abstract = {

Additive free aminolysis method developed for the depolymerization/upcycling of polycarbonates. We report here chemical recycling of polycarbonate under ambient conditions to get its monomer bisphenol A, monoaminocarbamate and biscarbamates in 1 : 2 : 1 ratio respectively. By employing the secondary amine as the aminating reagent, facilitates the depolymerization to work under additive/catalyst free conditions. The developed method deals with depolymerization of waste polycarbonates and works even with late-stage amine derivatives such as amoxapine and desloratadine which are drugs molecules known to treat neurotic disorders and allergies respectively. The reaction can be scaled up and works with similar efficacy which depicts the efficiency of the depolymerization of wasteend-of-life polycarbonate plastic waste. The biscarbamate and bisphenol-A was further subjected for the post functionalization to obtain amides and phenol in good yields. Developed additive/catalyst free aminolysis of waste polycarbonates to carbamates and monomer BPA at ambient conditions. Variety of secondary amines were screened including the late stage amine derivatives like amoxapine and desloratadine which delivered the expected products successfully. Later the developed methodology was even applied for the different end-of-life polycarbonates with the secondary amine and achieved the depolymerization without any obstacle. Further carried out the scale up reaction and derivatization of carbamates and BPA to amide and phenol synthesis. image

}, keywords = {Aminolysis, carbamates, depolymerization, End-of-life, Polycarbonate}, issn = {1864-5631}, doi = {10.1002/cssc.202400756}, author = {Padhi, Ganeshdev and Pansare, Vaibhav Ramachandra and Bajpai, Priyam and Krishna, Gamidi Rama and Vanka, Kumar and Barsu, Nagaraju} } @article {49522, title = {Ruthenium-catalyzed deconstruction of polyolefins: a strategy to up-cycle waste polyethylene to value-added alkene}, journal = {Angewandte Chemie-International Edition}, volume = {64}, year = {2025}, month = {APR}, type = {Article}, abstract = {

Synthesis of value-added products from post-consumer waste polyolefins is fascinating as well as challenging. Here we report ruthenium-catalyzed up-cycling of the polyethylene to long-chain alkene derivatives. The developed methodology mainly involves two steps i.e., dehydrogenation of polyethylene through hydrogen atom transfer and its metathesis using the HG-II catalyst. The dehydrogenation of polyethylene using ruthenium catalysis derived up to 3.38 \%, of double bonds; with 90 \% of the recovered polyolefin material. The obtained unsaturated polyethylene was subjected to cross-metathesis with ethylene using HG-II catalytic system. This resulted in the synthesis of predominantly dodecene (C12) derivatives, with 58 \% selectivity, along with other derivatives of varying chain lengths. The overall reaction produced terminal and internal olefins in the ratio 1:0.8 respectively. The dehydrogenation of polyethylene and its deconstruction was confirmed by NMR spectroscopy, Gel Permeation Chromatography (GPC) and Differential Scanning Calorimetry (DSC). The origin of C12 selectivity has been demonstrated by control experiments. The scope of the methodology was extended to post-consumer waste polyethylene which gave high conversion to value-added dodecene derivatives as a major product.

}, keywords = {Deconstruction, Homogeneous catalysis, ruthenium, Upcycling, Waste plastic}, doi = {10.1002/anie.202422609}, author = {Padhi, Ganeshdev and Khopade, Kishor V. and Moyilla, Nageswararao and Rangappa, Raghavendrakumar and Chikkali, Samir H. and Barsu, Nagaraju} } @article {49805, title = {Sustainable base-mediated chemical upcycling of poly (propylene carbonate) to β-hydroxy sulfides and oxides}, journal = {Green Chemistry}, volume = {27}, year = {2025}, month = {SEP}, pages = {10543-10549}, type = {Article}, abstract = {

We present a cesium carbonate-mediated method to upcycle poly(propylene carbonate) (PPC) waste into beta-hydroxy sulfides, selenides, and phenoxides via selective thermal depolymerization. The process tolerates diverse nucleophiles, including those from multilayer plastics. Mechanistic studies support a cesium aryl thiolate-driven nucleophilic degradation. The beta-hydroxy products are easily functionalized, and the base is recyclable, offering a sustainable route for PPC valorization.

}, issn = {1463-9262}, doi = {10.1039/d5gc02451j}, author = {Moyilla, Nageswararao and Padhi, Ganeshdev and Barsu, Nagaraju} }