Critical-size long bone defects remain a major clinical challenge, with treatments such as autografts or distraction osteogenesis causing donor-site morbidity, infection, or failure to restore complex bone architecture. Tissue-engineered implants that recapitulate native fracture healing provide a promising solution. However, scalability for dense cellular constructs is lacking. To address this, we bioprinted high-cell-density implants using rheologically competent sacrificial alginate bioinks. The constructs were supported by partially crosslinked alginate during bioprinting and chondrogenic differentiation, after which selective EDTA-mediated alginate dissolution generated scaffold-free implants. Quality characterization confirmed chondro-osteogenic signatures and extracellular matrix gene upregulation. Upon in vivo implantation in immunocompromised mice, implants underwent endochondral ossification, forming cortical and trabecular bone with bone marrow compartments. Integration with a suspension bioreactor enabled production of human-sized proof-of-concept implants. This work establishes a scalable 4D biofabrication process that integrates 3D bioprinting with dissolvable sacrificial alginate bioinks and results in scaffold-free, bone-forming callus implants.

Catalyst stability is one of many challenges encountered in olefin metathesis. Herein, we probe the behavior of first and second-generation alkene metathesis catalysts as a function of pressure and temperature in the ethenolysis of polybutadiene. Experimental data indicates that increased steric hindrance on the ancillary ligand tends to reduce decomposition pathways, as emphasized by the decrease of activity at high pressure and temperature with the SIMes ligand compared to SIPr.

The synthesis of phosphates via the oxidative coupling of alcohols and phosphites, catalyzed by iron(III) oxide, has been successfully achieved using elemental iodine and oxygen as oxidants. The protocol offers good to excellent yields with a broad range of substrates and remarkable environmental sustainability.

Abstract Ligand-directed regiodivergency is a trademark asset of transition metal–catalyzed olefin carbonylation, allowing facile diversification of unsaturated feedstocks. In contrast, carbonylative transfer hydrofunctionalization reactions that operate via shuttle catalysis are restricted by the need for specific wide bite-angle ligands, preventing access to both regioisomers. In addition, they are limited in scope and applicability. Here, we report a broadly applicable ligand-steered regiodivergent transfer hydrothiocarbonylation reaction that operates via Cl-assisted Pd catalysis. Spectroscopic, kinetic, and computational studies corroborate a dichotomous shuttling mechanism facilitated by dynamic chloride-thiolate ligand exchanges. The reaction is compatible with a myriad of functional handles and medicinally relevant heterocycles and can be used for late-stage functionalization of bioactive compounds. Further synthetic applications, such as 13C drug labeling and regiodivergent alcohol homologation, are demonstrated.

Introducing functionalities via acid‐mediated carbocation chemistry is conceptually straightforward, but typically lacks in selectivity and broad‐scale applicability, which is further hampered by the need for toxic reaction partners. Here, we show that small S‐ and Se‐based functionalities can be selectively and safely introduced into feedstock molecules via acid‐catalyzed transchalcogenation reactions. A designable y‐keto donor compound delivers the functionality through the formation of a trialkyl chalcogenonium intermediate that is prone to elimination in conjunction with the acid catalyst and its counteranion. We demonstrate how this strategy enables chemo‐, regio‐, and stereoselective construction of C(sp 3 )─S and ─Se bonds, offering clear advantages over classical acid‐catalyzed carbocation functionalization.

The chemical recycling of chlorinated plastics is industrially challenging due to the release of corrosive HCl and char formation. In this work, a novel upcycling route for chlorinated plastics, including polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), and chlorinated polyethylene (CPE), is developed. When ZnCl2-catalyzed dehydrochlorination (DHC) is combined with tandem DHC-hydrogenation, using a homogeneous Ru hydrogenation catalyst and metal oxides as a HCl trap, each plastic type can be selectively converted into an unsaturated polyolefin (UPO), which can be chemically split via metathesis. By rational design of reaction conditions, CPE (25 or 35 m% Cl) as a model substrate, a PVDC-PVC copolymer (66 m% Cl) and PVC (57 m% Cl) were consecutively converted into partially and fully dechlorinated UPOs. Both of these UPO products contained -CH2-CH2-sequences and up to 11 double bonds per 100 carbons. They were chemically split into alpha,omega-dienes using a second-generation Grubbs catalyst. Via this procedure, chlorinated plastics can be converted into valuable chemical building blocks, while the released HCl is sequestered.

Pd-catalyzed cross-coupling reactions are of key importance in the synthesis of C-C (linking, e.g., (hetero)aryls, alkenes, alkynes) and C-heteroatom bonds in the preparation of drug candidates. One such class of drug candidates encompasses peptides and peptidomimetics, where peptide-like motifs contribute to their biological activity. Despite its importance, direct C-C cross-coupling on the peptide backbone remains elusive. In this work, we demonstrate the utility of cationic Pd-phosphine complexes for C(sp(3))-C(sp(2)) (hetero)arylation of protected N-terminal glycine dipeptide fragments. The underlying catalytic mechanism was elucidated via kinetic experiments, computational modeling and isotope studies, and the synthesis of up to 50 medicinally relevant dipeptide carbon scaffolds was demonstrated.

Reactant diffusion efficiency plays a critical role in heterogeneous catalytic reactions. In this study, beta zeolite with a unique needle-like morphology was obtained through a designed cascade of postsynthesis treatments. The proposed formation mechanism for the needle-like morphology involves acid treatment to generate isolated silanol groups, followed by alkaline hydrothermal treatment using cetyltrimethylammonium bromide as a growth inhibitor, ultimately yielding the needle-like structure. Additionally, the mesopores created during these treatments-initially around 3.5 nm in size, larger than the conventional 3 nm-diminish with prolonged alkaline treatment and indicate significant morphological evolution beyond typical mesopore formation. These needle-like beta zeolites not only preserved the acidity of the original zeolite but also significantly increased the external surface area and hydrophobicity. Importantly, the intercrystalline spaces formed by the needle-like structure played a crucial role in enhancing catalytic activity, surpassing the impact of intracrystalline mesopores created by conventional methods. The influence of catalyst morphology-particularly the expanded external surface and intercrystalline mesoporosity-on the efficiency of this heterogeneous reaction is thoroughly discussed. Moreover, the turnover frequency for sorbitol conversion of the needle-like beta zeolite was 3-fold higher compared to the parent zeolite. This work advances the post-treatment methods of zeolites and holds significant potential for the utilization of biomass resources.

The use of non-renewable petrochemical feedstocks for the production of specialty polymer materials is not a sustainable practice. However, the use of waste commodity thermoplastic polymers as a feedstock for the production of specialty monomers is an attractive alternative. In this work, we show that high molar mass polybutadiene can be upcycled into reprocessable thermoset materials that can be recycled and reshaped multiple times as a dynamic covalent polymer network (DCPN). First, a one-pot partial hydrogenation and ethenolysis protocol was used to chemically cleave polybutadiene chains into low molecular weight α,ω-dienes. These were subsequently incorporated in a thiol-ene cured thermoset material using multifunctional thiols. The thioether linkages, connecting the polyolefin segments, can be turned into covalent dynamic moieties upon alkylation at elevated temperatures. The dynamic behavior of these thioether linkages was demonstrated through rheological and reprocessing experiments at elevated temperatures, highlighting their potential for sustainable material design. This strategy has a clear potential for an "upcycling" paradigm of bulk polymer waste into specialty polyolefin-based thermosets and DCPNs with appealing recyclability potential.

ITR zeolites exhibited excellent performance in methanol to propylene (MTP), where an important factor was the Al distribution of the ITR zeolites. However, optimization of the Al location in ITR zeolites in the conventional synthesis is challenging. In this work, the Al distribution in the ITR zeolites was efficiently adjusted by adding boron species in the synthesis gels due to the competitive occupancy of T sites in zeolites between boron and aluminum species. The obtained ITR with different boron content zeolites displayed similar nanosheet morphology, textural parameters, and strong acidic concentration but characterizations of Al distribution showed that the addition of boron species led to more Al species distributed in a relatively small sinusoidal channel and less Al species located in an intersection cavity. As a result, the aromatic cycle would be effectively suppressed due to the steric configuration of large aromatic cycle intermediates, whereas the alkene cycle will be enhanced correspondingly. As expected, catalytic tests in the conversion of MTP showed that the new ITR zeolites exhibited enhanced propylene selectivity and catalyst lifetime with the incorporation of boron species, which was attributed to different Al distribution in these ITR zeolites.

Nitrogen containing polymers (NCPs), particularly polyurethanes (PU) and polyamides (PA), play a crucial role in a wide range of industrial and consumer applications, leading to exponential growth in recent years. The production of both polymers relies primarily on fossil-fuel-derived monomers and lacks sustainable waste disposal solutions. To reduce fossil-fuel dependency, scaling up chemical recycling to an industrial scale is essential. Various systems have been developed at a lab scale, nevertheless, progress toward industrial-scale implementation remains scarce. This review provides a comprehensive overview of the main chemical recycling approaches. Systems already operating at an industrial scale are reviewed separately and a general comparison of all techniques is made for each polymer. Beyond technical aspects, this review highlights broader challenges, including concerns with economic feasibility, regulatory constraints related to handling toxic compounds, and logistical challenges in waste collection. The future perspective gives an update on the state-of-the-art of chemical recycling and outlines the current limitations toward a fully circular economy for the two major NCPs.

This study presents an efficient synthesis of styrene through a one-step C-H/C-H vinyl-aryl bond formation process, aiming to mitigate the need for harsh reaction conditions and the lack of step efficiency of the two-step industrial styrene production. In the ligand accelerated palladium(II)-catalyzed arene alkenylation, tunable 2-hydroxypyridine ligands were shown to enhance catalytic activity, stability, and selectivity. Reaction conditions were designed to obtain turnover numbers toward styrene exceeding 3200 with Pd concentrations ranging from 0.015 to 0.75 mM. Turnover frequencies of over 250 h-1 were recorded. A thorough mechanistic and spectroscopic study, involving kinetics, DFT calculations, ESI-MS, NMR, and XAS, proved that 2-hydroxypyridine-chelated Pd(II) is the species involved in C-H activation, with concerted metalation-deprotonation as the rate-determining step.

Strong metal-support interaction (SMSI) is a crucial factor in stabilizing metal nanoparticles (NPs) on reducible metal-oxides, affecting their dispersion, morphology, and catalytic properties. In this study, we show that tuning the synthesis protocol allows for the preparation of Pd/TiO2 catalysts with distinctly different metal-support interactions, and we investigate the underlying mechanisms behind these variations. Catalysts prepared via deposition-precipitation exhibit weak Pd-TiO2 interactions, whereas an evident SMSI effect is observed in the ones prepared by photodeposition. The latter samples demonstrate remarkable stability of the metallic phase even under high-temperature oxidizing conditions, unusual for Pd NPs. A comprehensive multi-technique study allowed attributing the SMSI effect to the presence of Ti3+ sites at the Pd/TiO2 interface, detected by electron paramagnetic resonance (EPR) and electron energy loss (EELS) spectroscopies, and direct Pd-Ti interactions, observed in X-ray absorption spectroscopy (XAS) data, in the photodeposited Pd/TiO2 catalyst. These features were not observed in the case of the deposition-precipitation method, due to the distinct formation mechanisms of the Pd NPs.

The search for non-halogenated, environmentally friendly flame retardants for plastics remains a major priority for industry. Current solutions rely mainly on the use of inorganic salts in high loading, which also alters the material properties. In this regard, phosphoramidate compounds have shown promising results at already low loadings in different polymeric materials; however, they still remain a relatively unexplored option. Here, we study the potential use of several phosphorus-based flame retardants (P-FR) for low density polyethylene (LDPE). Characterization of the prepared LDPE P-FR formulations showed minor differences between their physicochemical properties and those of the virgin LDPE polymer, while exhibiting a notable flame retardancy effect. Remarkably, the synthesized P-FR outperformed the commercially used inorganic salts when used at the same loadings. Finally, two potential methods for the valorization of waste LDPE were investigated to evaluate the effect of the P-FR on the chemical recyclability of the polymer.

Risk assessment of per- and polyfluoroalkyl substances (PFASs) requires accurate data on their fate in the environment. Current soil studies are generally based on short-term adsorption tests in soil spiked with PFAS, with limited attention to long-term reactions after that spiking (ageing) or to differences in solid-liquid partitioning between spiked and field-contaminated soils (field to spike). This study addressed both effects with a focus on perfluorooctanoate (PFOA), thereby using carrier-free C-14-labelled PFOA to discriminate the spiked from the field-originating PFOA. Short-term (48 h) adsorption of trace C-14-labelled PFOA in soils suspended in 0.01 M CaCl2 indicated linear sorption; the PFOA distribution (K-D) values ranged from 0.2 to 46 L kg(-1) (median 2.2 L kg(-1)) in 91 soil samples and correlated (p < 0.001) mainly with soil organic carbon (r = +0.65). Three soils were incubated up to 6 months after PFOA spiking. The desorption K-D values were only 1.7-2.8-fold higher than 48 h adsorption K-D values; these factors increased by ageing but plateaued 2-4 months after spiking. Field-contaminated soils were collected (n = 21, 0.5-1100 mu g PFOA kg(-1)). The PFOA desorption K-D was almost zero in field-contaminated soils with continuous fresh deposition and in soils with exceptionally high total PFAS concentrations (21000-53,000 mu g kg(-1)), the latter suggesting the formation of micelles facilitating desorption. In most other soils, PFOA desorption K-D values were similar to or maximally 1.6 times higher than corresponding C-14-PFOA adsorption K-D values measured in the same soils. Data suggest that PFOA adsorption is generally reversible and that small PFOA ageing effects observed in laboratory conditions at trace PFOA levels do not even occur in field conditions.

Acrylonitrile-based polymers are widely used in industrial and consumer settings, contributing to the growing amount of plastic waste. Yet, their chemical recycling has largely been neglected, partly due to the potential release of harmful gases such as HCN and NOx. Herein, we report a catalytic process that enables valorization of the polymer's N- and C-content, without releasing harmful nitrogen gases. Our strategy uses Pd-based shuttle catalysis to transfer HCN units from the polymer's backbone to an olefin acceptor molecule, generating a carbonaceous polyolefin residue amenable to further upcycling, alongside a useful nitrile building block. The protocol can be optimized in two ways: to efficiently functionalize olefins and produce nitriles in up to quantitative yields as a safe, cost-effective alternative to commonly employed nitrile synthesis methods, and to fully dehydrocyanate polymers using ethylene as HCN acceptor. Furthermore, we demonstrate the applicability of our strategy for the upcycling of commercial polyacrylonitrile materials.

Methylenedianiline (MDA) is a crucial intermediate for the production of methylenediphenyl diisocyanate (MDI), a key building block in polyurethane manufacturing. The traditional aniline synthesis, starting from petrochemical feedstocks, involves a hazardous and environmentally demanding multistep process (nitration, reduction). Consecutive condensation with formaldehyde and rearrangement to MDA are characterized by a challenging overall regioselectivity, resulting in an atom- and step-inefficient process. Herein, we report a sustainable amination process for the synthesis of MDA starting from bisphenols as an alternative and sustainable raw material. Pd/C was identified as a suitable catalyst, giving good yields (64%) with limited input of NH3 and H2. A low partial pressure of H2 facilitates the hydrogenation-amination-dehydrogenation pathway. The acid-base properties of the catalyst support strongly affect the reaction outcomes, which can be rationalized by the adsorption of the reactants and (intermediate) products. Through the addition of a potassium base (K2CO3, KOH) yields of up to 89% MDA and 97% diamines were obtained while limiting undesired side reactions like overhydrogenation of phenol to cyclohexanol and defunctionalization. Further insight into the reaction network was gained through dehydrogenation experiments; reaction parameters were related to NH3 temperature-programmed desorption (NH3-TPD) and CO-chemisorption catalyst characterization data.

Palladium(ii)-catalyzed dehydrogenative coupling of aliphatic olefins would enable an efficient route to (conjugated) dienes, but remains scarcely investigated. Here, 2-hydroxypyridine (2-OH-pyridine) was found to be an effective ligand for Pd(ii) in the activation of vinylic C(sp2)-H bonds. While reoxidation of Pd(0) is challenging in many catalytic oxidations, one can avoid in this reaction that the reoxidation becomes rate-limiting, even under ambient O2 pressure, by working in coordinating solvents. Via kinetic studies the elementary steps governing this reaction were elucidated, resulting in enhanced performance (turnover frequency) of the Pd(ii)/2-OH-pyridine system. The diene product is formed via a consecutive activation of two olefins on the same Pd atom, followed by a beta-hydride elimination. The first olefin activation, viz. the C-H activation, determines the overall reaction rate under these conditions. The catalytic complex was studied by ESI-MS and X-ray absorption spectroscopy, revealing that the coordination sphere of the working palladium complex contains two 2-OH-pyridine ligands.

The atom-efficient esterification of phosphoric acid was investigated for the selective synthesis of phosphate mono-esters using an acid treated niobium oxide catalyst, avoiding the use of amines as is common in literature. Kinetic studies revealed that the heterogeneous catalyst exhibited higher selectivity for mono-esters compared to homogeneous acid catalysts, as supported by calculation of the relative reactivity of mono-ester and phosphoric acid with different catalysts. To characterize the catalyst, its Hammett acidity value (H0) was determined, while solid state 31P NMR enabled studying the adsorption of H3PO4. Due to the mild acidity of the niobium oxide, alcohols with acid-sensitive functions, including substituted double bonds, could be phosphorylated, enabling the synthesis of surfactants such as oleyl phosphate.

ITR zeolite could be potentially used as catalysts in methanol to propylene (MTP), where their performance is strongly related to its Al distribution. However, the control of Al distribution in ITR zeolite poses a significant synthetic challenge. Herein, we demonstrate the possibility to control the Al distribution in ITR zeolites using zeolite A as an aluminum source (A-ITR). The A-ITR exhibited similar crystallinity, nanosheet morphology, textual parameters, and acidic concentration with those of conventional ITR made zeolites using aluminum isopropoxide as an aluminum source (C-ITR). Characterizations of the zeolite product with 27Al MQ MAS NMR spectra, 27Al MAS NMR spectra, and 1-hexene cracking reveal that the A-ITR zeolites have more Al species distributed in T6 and T8 sites located in relatively smaller micropores of the framework than C-ITR. As a result, the A-ITR gave enhanced catalyst lifetime and propylene selectivity due to the suppression of the aromatic cycle in the MTP reaction, compared with the C-ITR. This work provides an alternative approach to prepare efficient ITR zeolites for MTP reaction.