Modulating pore microenvironment in a robust ionic porous polymer for efficient propyne/propylene separation

A series of new metallosalen-based ionic porous organic polymers (POPs) were synthesized for the first time using a simple unique strategy based on the free-radical copolymerization reaction. Various techniques were used to characterize the physicochemical properties of these catalysts. These well-designed materials endowed high surface area, hierarchical porous structures, and enhanced CO2 /N2 adsorptive selectivity. Moreover, these POPs having both metal centers (Lewis acid) and ionic units (nucleophile) could serve as bifunctional catalysts in the catalytic conversion of CO2 into high value-added chemicals without any additional co-catalyst under mild and solvent-free conditions, for example, CO2 /epoxides cycloaddition and Nformylation of amines from CO2 and hydrosilanes. The results demonstrated that the irregular porous structure was very favorable for the diffusion of substrates and products, and the microporous structural property resulted in the enrichment of CO2 near the catalytic centers in the CO2 -involved transformations. Additionally, the superhydrophobic property could not only enhance the chemoselectivity of products but also promote the stability and recyclability of catalysts.

Structural design, preparation and characterization of light, isotropic and robust statically determined organic frameworks as reusable adsorbents

Carbon-carbon coupling is a basic design principle for the synthesis of porous organic polymers, which are widely used in gas adsorption/separation, photocatalysis, energy storage, etc. However, the C(sp3)-C(sp3) coupling reaction to construct porous organic polymers remains an important yet elusive objective due to its low reactivity and unknown side reactions. Herein, we report that nickel bis(1,5-cyclooctadiene) (Ni(COD)2), which was a famous catalyst for C(sp2)-C(sp2) coupling reactions, enables highly efficient C(sp3)-C(sp3) homo-coupling reactions to construct porous linear crystalline polymers and flexible three-dimensional porous aromatic frameworks (PAFs) under mild reaction conditions. The resulting linear polymers generated with dibromomethyl arenes have good crystallinity and high melting points (T m = 286 °C) due to controllability of reaction sites. Furthermore, the PAFs (PAF-64, PAF-65 and PAF-66) stemmed from tri-/tetra-bromomethyl arenes show high surface area (S BET = 390 m2 g-1) and high methane-storage capacity (up to 313 cm3 cm-3) because of their flexible frameworks. This work sheds new light on the construction of novel porous polymers through C(sp3)-C(sp3) coupling reactions and the development of methane-storage materials.

Efficient capture of CO2 and its conversion into other high value-added compounds by electrochemical methods is an effective way to reduce excess CO2 in the atmosphere. Porous polymeric materials hold great promise for selective adsorption and electrocatalytic reduction of CO2 due to their high specific surface area, tunable porosity, structural diversity, and chemical stability. Here, we review recent research advances in this field, including design of porous organic polymers (POPs), porous coordination polymers (PCPs), covalent organic frameworks (COFs), and functional nitrogen-containing polymers for capture and electrocatalytic reduction of CO2. In addition, key issues and prospects for the optimal design of porous polymers for future development are elucidated. This review is expected to shed new light on the development of advanced porous polymer electrocatalysts for efficient CO2 reduction.

Copper-incorporated porous organic polymer as efficient and recyclable catalyst for azide-alkyne cycloaddition

Porous organic polymers (POPs) show enormous potential for applications in separation, organic electronics, and biomedicine due to the combination of high porosity, high stability, and ease of functionalisation. However, POPs are usually insoluble and amorphous materials making it very challenging to obtain structural information. Additionally, important parameters such as the exact molecular structure or the crosslinking degree are largely unknown, despite their importance for the final properties of the system. In this work, we introduced the reversible multi-fold nitroxide exchange reaction to the synthesis of POPs to tune and at the same time follow the crosslinking degree in porous polymer materials. We synthesised three different POPs based on the combination of linear, trigonal, and tetrahedral alkoxyamines with a tetrahedral nitroxide. We could show that modulating the equilibrium in the nitroxide exchange reaction, by adding or removing one nitroxide species, leads to changes in the crosslinking degree. Being able to modulate the crosslinking degree in POPs allowed us to investigate both the influence of the crosslinking degree and the structure of the molecular components on the porosity. The crosslinking degree of the frameworks was characterised using EPR spectroscopy and the porosity was determined using argon gas adsorption measurements. To guide the design of POPs for desired applications, our study reveals that multiple factors need to be considered such as the structure of the molecular building blocks, the synthetic conditions, and the crosslinking degree.

Porous organic polymers with different pore structures for sensitive solid-phase microextraction of environmental organic pollutants

In recent years, ionic porous organic polymers (iPOPs) have emerged as a versatile class of materials, offering a unique combination of tunable porosity, high surface area, and physicochemical stability with charged skeletons, which enhances their functionality for diverse applications. However, their structural property relationship, which could be a decisive factor in designing high-performing ionic porous organic polymers, remains largely unexplored. Herein, we report the synthesis of three iPOPs (iPOP-IMZ-1, iPOP-IMZ-2, and iPOP-IMZ-3) using guanidinium-based primary building blocks and varying secondary building blocks to modulate charge density and optimize performance. The cationic polymers exhibited excellent adsorption capabilities for toxic oxo-anions and anionic dyes, addressing critical wastewater pollutants. Furthermore, their antibacterial properties were demonstrated via the membrane disruption of bacterial cells, highlighting their dual functionality. Scanning electron microscopy imaging suggested that the polymers exert their activity via a membrane disruption mechanism of action. This study provides insights into the structure–property relationship of iPOPs, emphasizing the critical role of secondary building blocks in tuning the material performance. These findings establish iPOPs as promising multifunctional materials for environmental remediation and antibacterial applications.

Herein, we present two novel ferrocene-containing porous organic polymers, FPOP-1 and FPOP-2, by the Heck reactions of 1,1′-divinylferrocene with two tetrahedral silicon-centered units, i.e., tetrakis(4-bromophenyl)silane and tetrakis(4′-bromo-[1,1′-biphenyl]-4-yl)silane. The resulting materials possess high thermal stability and moderate porosity with the Brunauer–Emmer–Teller (BET) surface areas of 499 m2 g−1 (FPOP-1) and 354 m2 g−1 (FPOP-2) and total pore volumes of 0.43 cm3 g−1 (FPOP-1) and 0.49 cm3 g−1 (FPOP-2). The porosity is comparable to previously reported ferrocene-containing porous polymers. These materials possess comparable CO2 capacities of 1.16 mmol g−1 (5.10 wt%) at 273 K and 1.0 bar, and 0.54 mmol g−1 (2.38 wt%) at 298 K and 1.0 bar (FPOP-1). The found capacities are comparable to, or higher than many porous polymers having similar or higher surface areas. They have high isosteric heats of up to 32.9 kJ mol−1, proving that the affinity between the polymer network and CO2 is high, which can be explained by the presence of ferrocene units in the porous networks. These results indicate that these materials can be promisingly utilized as candidates for the storage or capture of CO2. More ferrocene-containing porous polymers can be designed and synthesized by combining ferrocene units with various aromatic monomers under this strategy and their applications could be explored.

Chemical warfare agents (CWAs) have been a consistent a global concern with regard to both defence and civilian safety. In order to safeguard people from these harmful chemicals, numerous research teams have collaborated with defence organizations to find an advanced technological solution in terms of effectiveness and strength. In this context, porous organic polymers (POPs) have been thoroughly investigated as an ideal option for catalytically detoxifying CWAs by initially capturing them and subsequently transforming them into harmless chemicals. POPs are a new category of porous organic material, primarily made up of organic components linked by robust covalent bonds, resulting in highly interconnected frameworks with firm structures and defined voids for housing guest molecules. This review article offers a summary of current studies concerning different synthetic methods for POPs (HCPs, PIMs, and certain amorphous POPs), potential modifications to their functionality, and their promising use in photocatalytic/thermal detoxification of chemical warfare agents (CWAs). This review underscores the need for ongoing research to create effective, safe, and ecofriendly decontamination techniques. Ultimately, various catalytic processes of detoxification like hydrolysis and oxidation have been explored with POPs, and mechanisms were established through structure-activity relationships with various novel techniques. Additional needs and potential applications of utilizing POPs as nanoreactors for the detoxification of CWAs are also discussed.

Multifunctional porous organic polymers (POPs): Inverse adsorption of hydrogen over nitrogen, stabilization of Pd(0) nanoparticles, and catalytic cross-coupling reactions and reductions

Proton-exchange membrane fuel cells, emerging as green and sustainable energy sources, have attracted extensive attention in recent decades. Porous organic polymers, which feature in high surface area values, tunable pore sizes, excellent thermal and chemical stabilities, and the flexibility to incorporate specific functional groups, have recently displayed their striking images as potential electrolytes for fuel cells. In this work, BO-CMP-1 and BO-CMP-2 that possess rich π-structure and permanent porosity and have high thermal and chemical stability were synthesized through Suzuki-Miyaura coupling reaction. Owing to their rigid structures and abundant electrophilic substitution positions, these two novel porous polymers were covalently decorated with dense sulfonic acid groups by postsulfonation, as denoted by SBO-CMP-1 and SBO-CMP-2. The proton conductivity of SBO-CMPs is systematically studied to evaluate their performance as proton-conductive materials. It was found that their performance is highly humidity- and temperature-dependent and they show relatively high proton conductivity. For SBO-CMP-1 and SBO-CMP-2, their proton conductivities are 1.29 × 10-2 and 5.21 × 10-3 S cm-1, respectively, at 70 °C and 100% relative humidity. Low activation energy values of 0.32 eV for SBO-CMP-1 and 0.40 eV for SBO-CMP-2 suggest the Grotthuss mechanism for proton conduction.

A series of porous organic polymers (POPs) based on N-heterocyclic carbene (NHC) building blocks has been prepared through an octacarbonyldicobalt complex [Co2 (CO)8 ]-catalyzed trimerization of terminal alkyne groups. By changing the monomer ratio in the copolymerization, cross-linked POPs with tunable surface areas of 485-731 m2 g-1 and pore volumes of 0.31-0.51 cm3 g-1 were easily prepared. Compared with the analogues homogeneous NHC (SIPr) catalysts, the POPs exhibited an enhanced catalytic activity and high selectivity in the reductive functionalization of CO2 with amines. The extraordinary performance of the sample could be attributed to the combination of the gas enrichment (or storage) effect, enhanced in-pore concentrations of other substrates, and advantageous micropore structures of the porous polymers. Meanwhile, these catalysts can easily be separated and recycled from the reaction systems with only a slight loss of activity. This excellent catalytic performance and facile recycling of heterogeneous catalysts make them very attractive. These NHC-containing POPs may provide a new platform for catalytic transformations of CO2 .

A new triazine-thiophene based porous organic polymer as efficient catalyst for the synthesis of chromenes via multicomponent coupling and catalyst support for facile synthesis of HMF from carbohydrates

In recent years, the flexibility of porous organic polymers has demonstrated very unique properties during their applications. This paper reports a novel soluble porous polymer (named BIT-POP-75 and BIT-POP-75-OH) with 1,2-diketone and 1,2-diol subunits in the flexible polymer chain using contorted subunits. The solubility of the porous polymer and the flexible chelating 1,2-diol moiety facilitates the high loading and uniform dispersion of Pd nanoparticles to give the catalyst Pd@BIT-POP-75-OH, which shows high efficiency (kapp = 0.965 min-1) for the catalytic reduction of 4-nitrophenol with good recyclability (10 cycles).