Perspectives on green synthesis and catalysis

Despite their impressive capacity to access diverse functional groups and to synthesize structurally complex molecules,the majority of the organic reactions suffers from harsh conditions,low atom economy,and hazardous waste production.The goal of our research is geared towards developing efficient methods to minimize the adverse environmental impact and contributing to chemical sustainability.Herein,we illustrate three distinct green approaches,studying the novel reactivities with environmentally innocuous reagents to improve the synthetic efficiency,utilization of natural feedstocks,and employment of green energy to facilitate various important chemical transformations.From this perspective article,we hope to provide an overview of green synthetic chemistry and inspire the expansion of the field in the future.

Nano CuO/ZSM-5 zeolite as a green and efficient catalyst for dehydration of 1,4-butanediol to tetrahydrofuran

Nano CuO/ZSM-5 zeolite was prepared and used as a catalyst for dehydration of 1,4-butanediol(BDO) to tetrahydrofuran(THF) in liquid-phase. It was found that the 4.6 wt% CuO/ZSM-5 displayed good catalytic performance, and nearly 100%of BDO conversion and more than 99% of THF selectivity could be achieved by a rotary evaporator reactor at 170 °C under the atmospheric pressure. With such mild reaction conditions, 2400 g BDO could be converted to THF over 1 g catalyst under semi-continuous operation. Characterizations with X-ray diffraction(XRD), temperature-programmed reduction(TPR),NH3-temperature programmed desorption(TPD), X-ray photoelectron spectroscopy(XPS), transmission electron microscope(TEM) and Brunauer-Emmett-Teller(BET) over fresh and used 4.6 wt% CuO/ZSM-5 were conducted. Based on the results of the characterization and catalytic performance of 4.6 wt% CuO/ZSM-5, it can be conjectured that the formed 1–3 nm CuO nanoparticles, suitable acidity of the catalyst due to the synergic interaction of CuO and ZSM-5 support promoted the dehydration of BDO to THF.

Green Oxidation of Isochromans to Isochromanones with Molecular Oxygen Catalyzed by a Tetranuclear Vanadium Cluster

Comprehensive Summary Isochromanone is the core structure of many bioactive compounds.Direct oxidation of isochromans is one of leading methods for the construction of isochromanones,while most established processes remain suffering from the use of environmentally unfriendly metal oxidants,harsh reaction conditions,and the difficulty in catalyst recycling and product separation.Herein,we report a convenient,cost-effective,and green method for the synthesis of high-value added isochromanones via isochroman oxidations with O_(2) by a novel heterogeneous vanadium cluster catalyst(Cat.1)under mild conditions.This reaction protocol demonstrates high catalytic activity with good catalyst recyclability and reusability for a wide scope of substrates.

Recent advances in heterogeneous catalytic conversion of glucose to 5-hydroxymethylfurfural via green routes

With concerns of diminishing fossil fuel reserves and environmental deterioration, great efforts have been made to explore novel approaches of efficiently utilizing bio-renewable feedstocks to produce chemicals and fuels. 5-Hydroxymethylfurfural(HMF),generated from dehydration of six-carbon ketose, is regarded as a primary and versatile renewable building block to realize the goal of production of these high valued products from renewable biomass resources transformation. In this review, we summarize the recent advances via green routes in the heterogeneous reaction system for the catalytic production of HMF from glucose conversion, and emphasize reaction pathways of these reaction approaches based on the fundamental mechanistic chemistry as well as highlight the challenges(such as separation and purification of products, reusing and regeneration of catalyst, recycling solvent) in this field.

Supported Atomically Dispersed Pd Catalyzed Direct Alkoxylation and Allylic Alkylation

A new approach to allylic alkylation is realized using an atomically dispersed palladium catalyst(Pd1/TiO2-EG).Unlike conventional methods that require derivation of substrates and utilization of additives,this method allows for direct allylic alkylation from allylic alcohols,producing H2O as the sole by-product.The catalyst's high efficiency is attributed to the local hydrogen bonding at the or-ganic-inorganic interface(Pd-EG interface),facilitating hydroxyl group activation forη3π-allyl complex formation.The system demonstrates successful direct C—O and C—C coupling reactions with high selectivity,requiring no additives.This study highlights the potential of supported atomically dispersed catalysts for greener and more efficient catalysis,meanwhile,offers unique insights into the distinct behavior of atomically dispersed catalysts in comparison to homogeneous or nanoparticle-based catalysts.

Environmentally benign metal catalyst for the ring-opening copolymerization of epoxide and CO_(2): state-of-the-art, opportunities, and challenges

Carbon dioxide(CO_(2))is the main greenhouse gas,whereas it is also a nontoxic,abundant,cheap carbon and oxygen resource.The copolymerization of CO_(2) with epoxide presents a sustainable approach to the synthesis of biodegradable polymers,which upcycles the waste into wealth.Metal complex catalyst plays the central role in the reaction,since it provides oxophilic and Lewis acidic active center both for monomer activation and chain end stabilization,and nucleophiles as Lewis base for initiation.However,heavy metal catalyst with certain toxicity such as cobalt undisputedly dominates the copolymerization catalysis which comprises the overall sustainability.To circumvent the potential environmental hazard,developing highly active catalyst composed of green metals is of great importance especially when the polymer was utilized for agriculture purpose.This work reviews the development of sustainable metal catalysts for the production of CO_(2) copolymer,centered by Al,Mg,Ti,Fe,generally acknowledged as low toxic,environmentally benign,biocompatible,and also abundant in earth's crust.Emphasis is placed in recent five years where several historic examples are also included to construct a full picture of the sustainable catalysis explored to date.

An Environmentally Benign Catalytic Method for Versatile Synthesis of 1,4-Dihydropyridines via Multicomponent Reactions

The synthesis of diverse 1,4-dihydropyridines have been achieved via the multicomponent reactions of aldehydes,enaminones and amines.The reactions have been smoothly performed in water to provide all products with moderate to excellent yields by using lactic acid as a green catalyst.

Interfacing biosynthetic CdS with engineered Rhodopseudomonas palustris for efficient visible light-driven CO_(2)-CH_(4) conversion

Engineered photosynthetic bacterium Rhodo-pseudomonas palustris is excellent at one-step CO_(2) biomethanation and can use near-infrared light sources,overcoming the limitations of conventional photosynthetic systems.The current study constructed a biohybrid system that deposited CdS nanoparticles on R.palustris.This biohybrid system broadens the capture of sustainable solar energy,achieving a 155 nmol-mL-biological CH,production under full visible light irradiation,13.4-fold of that by the pure R.palustris.The transcriptome profiles revealed that gene expression related to photosynthetic electron transfer chain,nitrogenase,nanofilaments,and redox stress defense was activated.Accordingly,we attributed the much-enhanced CO_(2) biomethanation in the biohybrid system to the remarkable increase in the intracellular reducing power and the stronger rigidity of the cells assisted by photoexcited electrons from CdS nanoparticles.Our discovery offers insight and a promising strategy forimproving the current CO_(2)-CH_(4) biomanufacturing system.