Metalated Mesoporous Poly(triphenylphosphine) with Azo Functionality: Efficient Catalysts for CO2 Conversion

Functionalization of Magnetic UiO-66-NH2 with a Chiral Cu(l-proline)2 Complex as a Hybrid Asymmetric Catalyst for CO2 Conversion into Cyclic Carbonates

In this study, a chiral [Cu(l-proline)2] complex-modified Fe3O4@SiO2@UiO-66-NH2(Zr) metal-organic framework [Fe3O4@SiO2@UiO-66-NH-Cu(l-proline)2] via multifunctionalization strategies was designed and synthesized. One simple approach to chiralize an achiral MOF-structure that cannot be directly chiralized using a chiral secondary agent like 4-hydroxy-l-proline. Therefore, this chiral catalyst was synthesized with a simple and multistep method. Accordingly, Fe3O4@SiO2@UiO-66-NH2 has been synthesized via Fe3O4 modification with tetraethyl orthosilicate and subsequently with ZrCl4 and 2-aminoterephthalic acid. The presence of the silica layer helps to stabilize the Fe3O4 core, while the bonding between Zr4+ and the -OH groups in the silica layer promotes the development of Zr-MOFs on the Fe3O4 surface, and then the surfaces of the synthesized magnetic MOFs composite are functionalized with 1,2-dichloroethane and Cu(II) complex with 4-hydroxy-l-proline, [Cu(l-proline)2] to afford the magnetically chiral nanocatalyst. Multiple techniques were employed to characterize this magnetically chiral nanocatalyst such as Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectrometry (EDX), powder X-ray diffraction (PXRD), circular dichroism (CD), inductively coupled plasma (ICP), thermogravimetric analysis (TGA), vibrating-sample magnetometry (VSM), and Brunauer-Emmett-Teller (BET) analyses. Moreover, a magnetically chiral nanocatalyst shows the asymmetric CO2 fixation reaction under solvent-free conditions at 80 °C and in ethanol under reflux conditions with up to 99 and 98% ee, respectively. Furthermore, the reaction mechanism was illustrated concerning the total energy of the reactant, intermediates and product, and the structural parameters were analyzed.

Silver Metal-Organic Framework Derived N-Doped Carbon Nanofibers for CO2 Conversion into β-Oxopropylcarbamates

Developing efficient heterogeneous catalysts for chemical fixation of CO2 to produce high-value-added chemicals under mild conditions is highly desired but still challenging. Herein, we first reported an approach to prepare a novel catalyst (Ag@NCNFs), featuring Ag nanoparticles (NPs) embedded within porous nitrogen-doped carbon nanofibers (NCNFs), via growing a Ag metal-organic framework on one-dimensional electrospun nanofibers followed by pyrolysis. Benefiting from the abundant nitrogen species and porous structure, Ag NPs is well dispersed in the obtained Ag@NCNFs. Catalytic studies indicated that Ag@NCNFs exhibited excellent catalytic activity for the three-component coupling reaction of CO2, secondary amines, and propargylic alcohols to generate β-oxopropylcarbamates under mild conditions with a turnover number (TON) of 16.2, and it can be recycled and reused at least 5 times without an obvious decline in catalytic activity. The reaction mechanism was clearly clarified by FTIR, NMR, 13C isotope labeling, control experiments, and density functional theory calculations. The results suggest that Ag@NCNFs and 1,8-diazabicyclo[5.4.0]undec-7-ene can synergistically activate propargylic alcohol to react with CO2, and then the generated α-alkylidene cyclic carbonate was invaded by secondary amine to produce β-oxopropylcarbamate. Importantly, to the best of our knowledge, this is the first experimental and theoretical investigation on this reaction.

In Situ Anchoring of Small-Sized Silver Nanoparticles on Porphyrinic Triazine-Based Frameworks for the Conversion of CO2 into α-Alkylidene Cyclic Carbonates with Outstanding Catalytic Activities under Ambient Conditions

The preparation of catalytic hybrid materials by introducing highly dispersed metallic nanoparticles into porous organic polymers (POPs) may be an ideal and promising strategy for integrated CO2 capture and conversion. In terms of the carboxylative cyclization of propargyl alcohols with CO2, the anchoring of silver nanoparticles (AgNPs) on functional POPs to fabricate efficient heterogeneous catalysts is considered to be quite intriguing but remains challenging. In the contribution, well-dispersed AgNPs were successfully anchored onto the porphyrinic triazine-based frameworks by a simple "liquid impregnation and in situ reduction" strategy. The presence of N-rich dual active sites, porphyrin and triazine, which acted as the electron donor and acceptor, respectively, offered a huge opportunity for the nucleation and growth of metal nanoparticles. Significantly, the as-prepared catalyst Ag/TPP-CTF shows excellent catalytic activity (up to 99%) toward the carboxylative cyclization of propargyl alcohols with CO2 at room temperature, achieving record-breaking activities (TOF up to 615 h-1 at 1 bar and 3077 h-1 at 10 bar). Moreover, the catalyst can be easily recovered and reused at least 10 times with retention of high catalytic activity. The possible mechanism involves small-sized AgNP-mediated alkyne activation, which may promote highly efficient and green conversion of CO2. This work paves the way for immobilizing metal nanoparticles onto functional POPs by surface structure changes for enhanced CO2 catalysis.

Solution-processable polymers of intrinsic microporosity for gas-phase carbon dioxide photoreduction

Four solution-processable, linear conjugated polymers of intrinsic porosity are synthesised and tested for gas phase carbon dioxide photoreduction. The polymers' photoreduction efficiency is investigated as a function of their porosity, optical properties, energy levels and photoluminescence. All polymers successfully form carbon monoxide as the main product, without the addition of metal co-catalysts. The best performing single component polymer yields a rate of 66 μmol h^-1 m^-2, which we attribute to the polymer exhibiting macroporosity and the longest exciton lifetimes. The addition of copper iodide, as a source of a copper co-catalyst in the polymers shows an increase in rate, with the best performing polymer achieving a rate of 175 μmol h^-1 m^-2. The polymers are active for over 100 h under operating conditions. This work shows the potential of processable polymers of intrinsic porosity for use in the gas phase photoreduction of carbon dioxide towards solar fuels.

Sustainable synthesis of hydroxyl-functional porous organic framework as novel adsorbent for effective removal of organic micropollutants from water

Organic micropollutants (OMPs) in water resources are a growing threat to aquatic ecosystems and human health. Efficient removal of polar OMPs is very challenging because of their high hydrophility. Synthesizing novel adsorbent capable of high-efficiently removing hydrophilic and hydrophobic micropollutants is highly desirable for water remediation. Here, using natural proanthocyanidin as building units, a novel hydroxyl-functional porous organic framework (denoted as PC-POF) with amphiphilic feature was synthesized through facile azo coupling reaction. Five sulfonamide antibiotics were selected as model OMPs for adsorption study. Adsorption experiments demonstrated a more rapid and efficient sulfonamides capture ability of the PC-POF than that of the most reported adsorbents due to strong hydrogen bonding, π stacking and electrostatic interactions. The PC-POF can be easily recovered and reused at least 5 times without obvious decline in adsorption performance. Moreover, experiments conducted at environmentally relevant concentrations (μg L^-1) further confirmed a notable adsorption performance of the PC-POF even when the sulfonamides solution was rapidly passed through the PC-POF packed column. The PC-POF also showed good adsorption performance for other micropollutants like neonicotinoid insecticides, nitroimidazole antibiotics and triazine herbicides, indicating a promising prospect. This work provides a new strategy to construct amphiphilic adsorbent by using renewable resources for pollutants removal.

Porous Organic Polymers: Promising Testbed for Heterogeneous Reactive Oxygen Species Mediated Photocatalysis and Nonredox CO2 Fixation

Catalysts play a pivotal role in achieving the global need for food and energy. In this context, porous organic polymers (POPs) with high surface area, robust architecture, tunable pore size, and chemical functionalities have emerged as promising testbeds for heterogeneous catalysis. Amorphous POPs having functionalized interconnected hierarchical porous structures activate a diverse range of substrates through covalent/non-covalent interactions or act as a host matrix to encapsulate catalytically active metal centers. On the other hand, conjugated POPs have been explored for photoinduced chemical transformations. In this personal account, we have delineated the evolution of various POPs and the specific role of pores and pore functionalities in heterogeneous catalysis. Subsequently, we retrospect our journey over the last ten years towards designing and fabricating amorphous POPs for heterogeneous catalysis, specifically photocatalytic reactive oxygen species (ROS)-mediated organic transformations and nonredox chemical fixation of CO₂ . We have also outlined some of the future avenues of POPs and POP-based hybrid materials for diverse catalytic applications.

Exovinylene Cyclic Carbonates: Multifaceted CO2 -Based Building Blocks for Modern Chemistry and Polymer Science

Carbon dioxide is a renewable, inexhaustible, and cheap alternative to fossil resources for the production of fine chemicals and plastics. It can notably be converted into exovinylene cyclic carbonates, unique synthons gaining momentum for the preparation of an impressive range of important organic molecules and functional polymers, in reactions proceeding with 100 % atom economy under mild operating conditions in most cases. This Review summarizes the recent advances in their synthesis with particular attention on describing the catalysts needed for their preparation and discussing the unique reactivity of these CO₂ -based heterocycles for the construction of diverse organic building blocks and (functional) polymers. We also discuss the challenges and the future perspectives in the field.

En Route to CO2-Based (a)Cyclic Carbonates and Polycarbonates from Alcohols Substrates by Direct and Indirect Approaches

This review is dedicated to the state-of-the art routes used for the synthesis of CO2-based (a)cyclic carbonates and polycarbonates from alcohol substrates, with an emphasis on their respective main advantages and limitations. The first section reviews the synthesis of organic carbonates such as dialkyl carbonates or cyclic carbonates from the carbonation of alcohols. Many different synthetic strategies have been reported (dehydrative condensation, the alkylation route, the “leaving group” strategy, the carbodiimide route, the protected alcohols route, etc.) with various substrates (mono-alcohols, diols, allyl alcohols, halohydrins, propargylic alcohols, etc.). The second section reviews the formation of polycarbonates via the direct copolymerization of CO2 with diols, as well as the ring-opening polymerization route. Finally, polycondensation processes involving CO2-based dimethyl and diphenyl carbonates with aliphatic and aromatic diols are described.

Strategic design of a bifunctional Ag(i)-grafted NHC-MOF for efficient chemical fixation of CO2 from a dilute gas under ambient conditions

Facile grafting of catalytically active Ag(i) into CO2-philic NHC-MOF for simultaneous capture and conversion of CO2 from dilute gas to value-added α-alkylidene cyclic carbonate and oxazolidinones under mild conditions is demonstrated.

A heterogeneous bifunctional silica-supported Ag2O/Im+Cl− catalyst for efficient CO2 conversion

Reusable heterogeneous bifunctional silica-supported Ag2O/Im+Cl− catalyst in carboxylative cyclization reaction of propargyl alcohols by the efficient utilization of CO2 under ambient conditions.

Metal Organic Frameworks as Heterogeneous Catalysts in Olefin Epoxidation and Carbon Dioxide Cycloaddition

Metal–organic frameworks (MOFs) are a family of porous crystalline materials that serve in some cases as versatile platforms for catalysis. In this review, we overview the recent developments about the use of these species as heterogeneous catalysts in olefin epoxidation and carbon dioxide cycloaddition. We report the most important results obtained in this field relating them to the presence of specific organic linkers, metal nodes or clusters and mixed-metal species. Recent advances obtained with MOF nanocomposites were also described. Finally we compare the results and summarize the major insights in specific Tables, outlining the major challenges for this emerging field. This work could promote new research aimed at producing coordination polymers and MOFs able to catalyse a broader range of CO2 consuming reactions.

Phosphorus containing porous organic polymers: synthetic techniques and applications in organic synthesis and catalysis

The phosphorus-containing porous organic polymer is a trending material for the synthesis of heterogeneous catalysts. Decades of investigations have established phosphines as versatile ligands in homogeneous catalysis. Recently, phosphine-based heterogeneous catalysts were synthesized to exploit the same electronic properties while leveraging extra stability and reusability. In the last few decades, the catalysts were applied in diverse organic transformations, including hydroformylation, hydrogenation, C-C, C-N and C-X coupling, hydrosilylation, oxidative-carbonylation reactions, and so on. However, even though these polymers possess a multifunctional character, they face multiple synthetic issues in controlling the pore size, increasing the surface area, and creating a single type of active site. This review summarizes the developments in this field over the last few decades, highlighting the current limitation and future scope.

A dual-functional urea-linked conjugated porous polymer anchoring silver nanoparticles for highly efficient CO2 conversion under mild conditions

A dual-functional urea-linked conjugated porous polymer (UCPP) assembled by enol-imine with ordered unit arrays that act as potential anchoring sites in the networks was fabricated, and was further applied as a support for Ag nanoparticles by the coordinate interaction between them. The UCPP not only can well confine the Ag particle size and facilitate high dispersion, but also can afford special CO₂-philic moieties to enhance the adsorption properties. The resulting Ag@UCPP as a heterogeneous catalyst exhibited excellent activity for the carboxylative cyclization of propargyl alcohols with CO₂ under mild conditions, together with good recyclability, which is probably attributed to the synergistic effect of the UCPP on the adsorption and activation of CO₂ and the immobilization of Ag nanoparticles. This work affords possible opportunities for the design and synthesis of a heterogeneous catalyst toward CO₂ conversion.

Solvent-Dependent Assembly and Magnetic Relaxation Behaviors of [Cu4I3] Cluster-Based Lanthanide MOFs: Acting as Efficient Catalysts for Carbon Dioxide Conversion with Propargylic Alcohols

Two structurally similar metal-organic frameworks (MOFs) [Dy₂Cu₄I₃(IN)₇(DMF)₂]·DMF (1) and [Dy₂Cu₄I₃(IN)₇(DMA)₂]·DMA (2) (HIN = isonicotinic acid) feathering different coordinated solvent molecules were successfully isolated by tuning the types of solvents in the reaction system. Structural tests indicate that 1 and 2 are both built from 1D Dy(III) chains and copper iodide clusters [Cu₄I₃], generating into three-dimensional frameworks with an open 1D channel along the a axis. 1 and 2 display extensive and excellent solvent stability. Magnetic studies of 1 and 2 indicate that they exhibit interesting solvent-dependent magnetization dynamics. Importantly, 1 and 2 can act as highly effective catalysts for the carboxylic cyclization of propargyl alcohols with carbon dioxide (CO₂) under ambient operating conditions. Additionally, the substrate scope was further explored over compound 1 based on the optimal conditions, and it exhibits efficient cyclic carboxylation of various terminal propargylic alcohols with CO₂. This research offers an effective approach for the solvent-guided synthesis of MOFs materials and also presents the great application value of MOFs in CO₂ chemical conversion.

Formation of CX Bonds in CO2 Chemical Fixation Catalyzed by Metal-Organic Frameworks

Transformation of CO₂ based on metal-organic framework (MOF) catalysts is becoming a hot research topic, not only because it will help to reduce greenhouse gas emission, but also because it will allow for the production of valuable chemicals. In addition, a large number of impressive products have been synthesized by utilizing CO₂ . In fact, it is the formation of new covalent bonds between CO₂ and substrate molecules that successfully result in CO₂ solidly inserting into the products, and only four types of new CX bonds, including CH, CC, CN, and CO bonds, are observed in this exploration. An overview of recent progress in constructing CX bonds for CO₂ conversion catalyzed by various MOF catalysts is provided. The catalytic mechanism of generating different CX bonds is further discussed according to both structural features of MOFs and the interactions among CO₂ , substrates, as well as MOFs. The future opportunities and challenges in this field are also tentatively covered.

Triazinetriamine-derived porous organic polymer-supported copper nanoparticles (Cu-NPs@TzTa-POP): an efficient catalyst for the synthesis of N-methylated products via CO2 fixation and primary carbamates from alcohols and urea

Copper nanoparticles incorporated triazinetriamine derived porous organic polymer based catalyst was synthesized for catalytic production N-methylated amines and primary carbamates.

A Versatile Porous Silver-Coordinated Material for the Heterogeneous Catalysis of Chemical Conversion with Propargylic Alcohols and CO2

The efficient transformation of carbon dioxide into useful chemical feedstock is of great significance, attracting intense research interest. The widely studied porous-coordinated polymers possess large pores to adsorb guest molecules and further allow the contact and to transfer the substrate molecule within their microenvironment. Here we present the synthesis of a silver-based metal-organic frameworks (MOFs) material with a three-dimensional structure by incorporating a tetraphenyl-ethylene moiety as the four-point connected node via the solvothermal method. This polymer exhibits as an efficient heterogeneous catalyst for the carboxylative cyclization of CO₂ to α-methylene cyclic carbonates in excellent yields. Moreover, the introduction of silver (Ag (I)) chains in this framework shows the specific alkynophilicity to activate C≡C bonds in propargylic alcohols to greatly accelerate the efficient conversion, and the large pores in the catalyst exhibit a size-selective catalytic performance.

Topotactic Synthesis of Phosphabenzene-Functionalized Porous Organic Polymers: Efficient Ligands in CO2 Conversion

Progress toward the preparation of porous organic polymers (POPs) with task-specific functionalities has been exceedingly slow-especially where polymers containing low-oxidation phosphorus in the structure are concerned. A two-step topotactic pathway for the preparation of phosphabenzene-based POPs (Phos-POPs) under metal-free conditions is reported, without the use of unstable phosphorus-based monomers. The synthetic route allows additional functionalities to be introduced into the porous polymer framework with ease. As an example, partially fluorinated Phos-POPs (F-Phos-POPs) were obtained with a surface area of up to 591 m²  g^-1 . After coordination with Ru species, a Ru/F-Phos-POPs catalyst exhibited high catalytic efficiency in the formylation of amines (turnover frequency up to 204 h^-1 ) using a CO₂ /H₂ mixture, in comparison with the non-fluorinated analogue (43 h^-1 ) and a Au/TiO₂ heterogeneous catalysts reported previously (<44 h^-1 ). This work describes a practical method for synthesis of porous organic phosphorus-based polymers with applications in transition-metal-based heterogeneous catalysis.

Meso–macroporous organic polymer-supported homogeneously dispersed small Pd nanoparticles obtained by a simple ion-exchange approach for the Heck reaction

Herein, a meso–macroporous organic polymer-supported Pd nanoparticle catalyst (Pd/MOP-I) with homogeneously dispersed small Pd NPs (ca. 2.4 nm) was synthesized by a simple ion-exchange approach.

A rose bengal-functionalized porous organic polymer for carboxylative cyclization of propargyl alcohols with CO2

Rose bengal-functionalized polymer (RB-POP) supported Ag nanoparticles exhibited excellent performance for catalysing carboxylative cyclization of propargyl alcohols with CO₂.

Palladium/phosphorus-functionalized porous organic polymer with tunable surface wettability for water-mediated Suzuki–Miyaura coupling reaction

A series of phosphorus-functionalized porous organic polymers supported palladium catalysts with tunable surface wettability were successfully prepared using an easy copolymerization and successive immobilization method. The obtained polymers were carefully characterized by many physicochemical methods. Characterization results suggested that the prepared materials featured hierarchically porous structures, high pore volumes, tunable surface wettability and strong electron-donating ability towards palladium species. We demonstrated the use of these solid catalysts for water-mediated Suzuki–Miyaura coupling reactions. It was found that the surface wettability of the prepared catalysts has an important influence on their catalytic activities. The optimal catalyst, which has excellent amphipathicity and relatively high phosphorus concentration, displayed superior catalytic activity compared to the other catalysts. Under ambient conditions, a variety of aryl chlorides can be efficiently transformed to biaryls in high yields. Moreover, the catalyst could be easily recovered and reused at least six times.

A palladium/phosphorus-functionalized porous organic polymer with tunable surface wettability was successfully prepared. The catalyst displayed high catalytic activity for the water-mediated Suzuki–Miyaura coupling reaction of aryl chlorides.