Schiff-base Polymer Immobilized Ruthenium for Efficient Catalytic Cross-coupling of Secondary Alcohols with 2-amino- and γ-aminobenzyl Alcohols to Give Quinolines and Pyridines

A Schiff-base porous polymer has been impregnated with ruthenium trichloride for acceptor-free dehydrogenation coupling (ADC) of secondary alcohols with γ-amino- and 2-aminobenzyl alcohols to give pyridines and quinolines. This heterogenous catalyst exhibited high catalytic efficiency over repeated cycles with wide functional group tolerance.

Selective CO2 Electroreduction from Tuneable Naphthalene-Based Porous Polyimide Networks

A series of porous polyimides (pPIs) are synthesized, and their surface areas and pore sizes are optimized by the previously reported Bristol-X'an-Jiatong (BXJ) approach. How this approach can be used to tune and optimize the porous network properties to target and tune their ability to capture CO₂ is demonstrated. Once optimized, these porous organic frameworks are utilized, for the first time, as electrocatalysts for the conversion of CO₂ . The excellent Faradaic efficiencies (FEs) for the conversion of CO₂ to formate (91%) and methanol (85%) present exciting opportunities for the metal-free generation of useful fuels and feedstocks from CO₂ . In addition, the ability to directly address and select the conversion products through tuning of the porous materials' properties highlights the potential of this approach, and more generally for a wide range of organic frameworks as future metal-free CO₂ reduction catalysts.

Nanoporous {Y2}-Organic Frameworks for Excellent Catalytic Performance on the Cycloaddition Reaction of Epoxides with CO2 and Deacetalization-Knoevenagel Condensation

Stable metal-organic frameworks containing periodically arranged nanosized pores and active Lewis acid-base active sites are considered as ideal candidates for efficient heterogeneous catalysis. Herein, the exquisite combination of [Y₂(CO₂)₇(H₂O)₂] cluster (abbreviated as {Y₂}) and multifunctional linker of 2,4,6-tri(2,4-dicarboxyphenyl)pyridine (H₆TDP) led to a nanoporous framework of {[Y₂(TDP)(H₂O)₂]·5H₂O·4DMF}_n (NUC-53, NUC = North University of China), which is a rarely reported binuclear three-dimensional (3D) framework with hierarchical tetragonal-microporous (0.78 nm) and octagonal-nanoporous (1.75 nm) channels. The inner walls of these channels are aligned by {Y₂} clusters and plentifully coexisted Lewis acid-base sites of Y^III ions and N_pyridine atoms. Furthermore, NUC-53 has a quite large void volume of ∼65.2%, which is significantly higher than most documented 3D rare-earth-based MOFs. The performed catalytic experiments exhibited that activated NUC-53 showed a high catalytic activity on the cycloaddition reactions of CO₂ with styrene oxide under mild conditions with excellent turnover number (TON: 1980) and turnover frequency (TOF: 495 h^-1). Moreover, the deacetalization-Knoevenagel condensation reactions of benzaldehyde dimethyl acetal and malononitrile could be efficiently prompted by the heterogeneous catalyst of NUC-53. These findings not only pave the way for the construction of nanoporous MOF based on rare-earth clusters with a variety of catalytic activities but also provide some new insights into the catalytic mechanism.

6s-3d {Ba3Zn4}-Organic Framework as an Effective Heterogeneous Catalyst for Chemical Fixation of CO2 and Knoevenagel Condensation Reaction

The exquisite combination of Ba²⁺ and Zn²⁺ with the aid of 2,4,6-tri(2,4-dicarboxyphenyl)pyridine (H₆TDP) under the condition of solvothermal self-assembly generates one highly robust [Ba₃Zn₄(CO₂)₁₂(HCO₂)₂(OH₂)₂]-organic framework of {[Ba₃Zn₄(TDP)₂(HCO₂)₂(OH₂)₂]·7DMF·4H₂O}_n (NUC-27), in which adjacent 2D layers are interlaced via hydrogen-bonding interactions to form a 3D skeleton with peapod-like channels and nano-caged voids. It is worth emphasizing that both Ba²⁺ and Zn²⁺ ions in NUC-27 display the extremely low coordination modes: hexa-coordinated [Ba(1)] and tetra-coordinated [Ba(2), Zn(1), and Zn(2)]. Furthermore, to the best our knowledge, NUC-27 is one scarcely reported 2D-based nanomaterial with an unprecedented Z-shaped hepta-nuclear heterometallic cluster of [Ba₃Zn₄(CO₂)₁₂(HCO₂)₂(OH₂)₂] as SBUs, which not only has plentiful low-coordinated open metal sites but also has the excellent physicochemical properties including omni-directional opening pores, ultrahigh porosity, larger specific surface area, and the coexistence of Lewis acid-base sites. Just as expected, thanks to its rich active metal sites and pyridine groups as strong Lewis acid-base roles, completely activated NUC-27 displays high catalytic efficiency on the chemical transformation of epoxides with CO₂ into cyclic carbonates under mild conditions and effectively accelerates the reaction process of Knoevenagel condensation.

Crosslinked porous polyimides: structure, properties and applications

Porous polyimides (pPIs) represent a fascinating class of porous organic polymers (POPs). Here the properties and functions of amorphous and crystalline pPIs are reviewed, and applications contributing to solutions to global challenges highlighted.

Organocatalytic carbon dioxide fixation to epoxides by perfluorinated 1,3,5-triols catalysts

In order to improve epoxides conversion to carbonates by fixation of CO2 a new type of perfluorinated triol catalysts was developed. These simple acyclic scaffolds of enhanced acidity are efficient for catalysis through selective H-bonding activation of the epoxide. In combination with TBAI as co-catalyst, this useful transformation is performed under only 1 atmosphere of CO2 and between 30 to 80 °C. Both the 1,3,5-triol motif and the perfluorinated side chains are crucial in order to observe this epoxide opening under such mild conditions. In addition, the stereochemistry of the starting epoxide can efficiently be conserved during the carbonate formation.