Triptycene-Based Microporous Cyanate Resins for Adsorption/Separations of Benzene/Cyclohexane and Carbon Dioxide Gas

Triptycene-based cyanate monomers 2,6,14-tricyanatotriptycene (TPC) and 2,6,14-tris­(4-cyanato­phenyl)­triptycene (TPPC) that contain different numbers of benzene rings per molecule were synthesized, from which two microporous cyanate resins PCN–TPC and PCN–TPPC were prepared. Of interest is the observation that the two polymers have very similar porosity parameters, but PCN-TPPC uptakes considerably higher benzene (77.8 wt %) than PCN-TPC (17.6 wt %) at room temperature since the higher concentration of phenyl groups in PCN-TPPC enhances the π–π interaction with benzene molecules. Besides, the adsorption capacity of benzene in PCN-TPPC is dramatically 7 times as high as that of cyclohexane. Contrary to the adsorption of organic vapors, at 273 K and 1.0 bar, PCN-TPC with more heteroatoms in the network skeleton displays larger uptake of CO₂ and higher CO₂/N₂ selectivity (16.4 wt %, 60) than those of PCN-TPPC (14.0 wt %, 39). The excellent and unique adsorption properties exhibit potential applications in the purification of small molecular organic hydrocarbons, e.g., separation of benzene from benzene/cyclohexane mixture as well as CO₂ capture from flue gas. Moreover, the results are helpful for deeply understanding the effect of porous and chemical structures on the adsorption properties of organic hydrocarbons and CO₂ gas

Naphthalene-Based Microporous Polyimides: Adsorption Behavior of CO₂ and Toxic Organic Vapors and Their Separation from Other Gases

Naphthalene was selected as a building block to prepare three polyimide networks with different topological structures via one-pot polycondensation from naphthalene-1,4,5,8-tetracarboxylic dianhydride with tetrakis­(4-aminophenyl)­methane, tris­(4-aminophenyl)­amine, and 1,3,5-tris­(4-aminophenyl)­benzene. The resultant polymers have moderately large BET surface areas with narrow pore size distribution at around 6 Å. Interestingly, it is found that they can uptake 90.5 wt % benzene vapor (298 K, 0.8 bar), and the separation factors of benzene over nitrogen, water, and cyclohexane are as high as 759.3, 40.3, and 13.8, respectively. The high adsorption capacity and selectivity of benzene vapor are attributed to the incorporation of large amount of naphthalene groups in the network since naphthalene is highly hydrophobic in nature and has strong π-electron-delocalization effect. On the other hand, the CO₂ uptakes in polymers reach 12.3 wt % (273 K, 1 bar), and the adsorption curves are reversible. Moreover, the separation factors of CO₂/N₂ and CO₂/CH₄ are 88.6 and 12.9, respectively, superior to many other microporous organic polymers. The above experimental results were analyzed and explained with respect to the kinetic diameters, polarity, critical temperature of the vapors and gases, and the stereoconfiguration of net nodes, porous characteristics, and hydrophobic/hydrophilic nature of the pore walls of the microporous polyimides

Tetraphenyladamantane-Based Microporous Polyimide and Its Nitro-Functionalization for Highly Efficient CO₂ Capture

A new microporous polyimide network (PI-ADNT) is synthesized from 1,3,5,7-tetrakis­(4-aminophenyl)­adamantane and naphthalene-1,4,5,8-tetracarboxylic dianhydride. Subsequently, PI-ADNT is nitrated in fuming nitric acid with different nitration time to produce three nitro-decorated porous polyimides (PI-NO₂s). Their chemical structures and nitration degrees are characterized by FTIR, solid-state ¹³C CP/MAS NMR spectra and element analysis. The interesting evolution of porous morphology and porosity of PI-NO₂s with nitration time is investigated in detail. The results show that PI-ADNT has the BET surface area of 774 m² g^–1 with microporous size centering at 0.75 nm. After nitration-modifications, PI-NO₂s display decreased surface area but remarkably increased CO₂ uptake up to 4.03 mmol g^–1, which is superior to most of porous polymers reported in the literature. Moreover, the CO₂ adsorption selectivites over CH₄ and N₂ in PI-NO₂s are also significantly improved in comparison with PI-ADNT. The CO₂ adsorption/separation properties of PI-ADNT and its nitrated products are studied and explained in terms of the variations of porous structure and chemical composition as well as the interaction parameters between CO₂ molecule and polymer skeleton such as Henry’s constant, first virial coefficient, and enthalpy of adsorption

Facile Synthesis of Fluorinated Microporous Polyaminals for Adsorption of Carbon Dioxide and Selectivities over Nitrogen and Methane

Monoaldehyde compounds, benzaldehyde, 4-methyl­benzaldehyde, 4-fluoro­benzaldehyde, and 4-trifluoro­methyl­benzaldehyde, were utilized to react with melamine respectively to yield four hyper-cross-linked microporous polyaminal networks, PAN-P, PAN-MP, PAN-FP, and PAN-FMP, via a facile “one-step” polycondensation without adding any catalyst. It is found that relative to non-fluorinated polymers the fluorinated ones show the increased BET specific surface areas from 615 to 907 m² g^–1. Moreover, the incorporations of methyl and trifluoromethyl on the phenyl rings can effectively tailor the pore sizes from 0.9 to 0.6 nm. The polar C–F bond and nitrogen-rich polyaminal skeleton result in high CO₂ adsorption enthalpies (38.7 kJ mol^–1) and thereby raise the CO₂ uptake up to 14.6 wt % (273 K, 1 bar) as well as large CO₂/N₂ and CO₂/CH₄ selectivities of 78.1 and 13.4 by the ideal adsorbed solution theory, respectively. The facile and scalable preparation method, low cost, and large CO₂ adsorption and selectivities over N₂ and CH₄ endow the resultant microporous polyaminals with promising applications in CO₂-capture from flue gas and natural gas

Highly Selective Separation of CO₂, CH₄, and C₂–C₄ Hydrocarbons in Ultramicroporous Semicycloaliphatic Polyimides

Ultramicroporous semicycloaliphatic polyimides with major pore sizes less than 0.5 nm are synthesized through imidization reaction between different aromatic tetraamines and cycloaliphatic dianhydrides. The synergistic role of abundant CO₂-philic imide rings and the molecular sieving effect of ultrasmall pores in the polyimide network bring about high adsorption selectivity of CO₂/CH₄ (37.2) and CO₂/N₂ (136.7). In addition, it is interesting to observe that, under ambient condition (298 K/1 bar), <i>n</i>-butane exhibits the highest uptake (3.15 mmol/g) among the C₁–C₄ alkanes, and the adsorbed amount significantly drops with the reduction of the number of carbon atoms. As a result, the mixed light alkanes can be effectively separated according to the carbon numbers. The separation factors of <i>n</i>-butane/propane and propane/ethane reach 3.1 and 6.5, whereas those of <i>n</i>-butane, propane, and ethane over methane are as high as 414.5, 217.4, and 19.6, respectively. Moreover, the polyimides display large adsorption capacities for 1,3-butadiene (4.64 mmol/g) and propene (2.68 mmol/g) with good selectivity over 1-butene and propane of 3.2 and 3.0, respectively. Together with the excellent thermal and physicochemical stabilities, the ultramicroporous polyimides obtained in this work show promising applications in adsorption/separation for CO₂, CH₄, and C₂–C₄ hydrocarbons

Ultramicroporous Carbons Derived from Semi-Cycloaliphatic Polyimide with Outstanding Adsorption Properties for H₂, CO₂, and Organic Vapors

Ultramicroporous carbons (UMC-<i>T</i>s) have been successfully prepared using nitrogen- and oxygen-rich porous semicycloaliphatic polyimide as a precursor in the presence of KOH at different carbonization temperatures of 600, 700, and 800 °C, respectively. The evolution of porous and chemical structures of the resultant carbons in the course of carbonization as well as their effects on adsorption of H₂, CO₂, benzene, and cyclohexane are studied in detail. Compared with the porous polyimide precursor, after carbonization treatment, the products exhibit the significantly increased BET specific surface areas from 900 to 2406 m² g^–1 and create large amounts of ultramicropores with the pore size smaller than 0.5 nm, leading to outstanding adsorption capacities for CO₂ (34.0 wt %, 273 K/1 bar) and H₂ (3.7 wt %, 77 K/1 bar). Moreover, it is interesting to observe that UMC-<i>T</i>s possess extraordinarily large uptake for benzene (74.4 wt %, 298 K) and cyclohexane (64.8 wt %, 298 K) at the very low relative pressure (<i>P</i>/<i>P</i>₀ = 0.1), showing promising applications in CO₂ capture, H₂ storage, and removal of toxic organic vapors

Heat-Resistant Crack-Free Superhydrophobic Polydivinylbenzene Colloidal Films

Highly cross-linked poly­(divinylbenzene) (PDVB) spherical colloidal particles with nano-, submicron-, and micron-sizes of 157.2 nm, 602.1 nm, and 5.1 μm were synthesized through emulsion and dispersion polymerization methods. The influences of particle size on the surface morphology, roughness, superhydrophobicity, and critical cracking thickness of colloidal films were studied in detail. The results show that PDVB colloidal films possess large water contact angle (CA) over 151°, belonging to superhydrophobic materials. Moreover, it is interesting to observe that the highly cross-linked network structure leads to PDVB film’s excellent heat-resistance. The CA and rough surface morphology remain nearly unchanged after thermal-treatment of films at 150 °C for 24 h. In addition, no cracks were observed in films with thicknesses up to 8.1 μm, exceeding most of polymer and inorganic particle films reported in the literature. The simple and scalable preparation method, low-cost, superhydrophobicity, and excellent thermal stability endow the PDVB colloidal films with promising applications in advanced coating fields, especially when employed in the high-temperature service environment

Synthesis of Fluorescent Micro- and Mesoporous Polyaminals for Detection of Toxic Pesticides

This paper presents the first report on employing fluorescent porous organic polymers as sensors for the detection of toxic pesticides. Specifically, fluorescent micro- and mesoporous polyaminals with pendant triphenylamine and dibromotriphenylamine chromophore groups are synthesized, which exhibit BET surface area up to 507 m² g^–1, adjustable pore sizes in the range from 0.5 to 36.2 nm and can emit bright turquoise light under the ultraviolet lamp. Using the insecticide (fenitrothion) and herbicides (trifluralin and glyphosate) as analytes, the chemosensing properties are investigated by correlating the porosity parameters and chemical structure of the polymers with the molecular sizes and the energy in the lowest unoccupied molecular orbital of pesticides. Moreover, the effects of different acid–base conditions and solvents including ethanol, water, chloroform, tetrahydrofuran, and <i>N</i>,<i>N</i>-dimethyl­formamide on the chemosensing sensitivity of the polymers are also studied in detail. Particularly, the chemosensing test paper fabricated with the fluorescent polymer rapidly becomes dark upon contacting the pesticide solutions at an extremely low concentration, and the quenching degree is unchanged after repeating the experiments for 10 times, exhibiting the capability of sensible and reusable detection for pesticides

Tetraphenyladamantane-Based Polyaminals for Highly Efficient Captures of CO₂ and Organic Vapors

Tetraphenyladamantane-based polyaminals with ultrasmall pore, large specific surface area and abundant CO₂-philic aminal groups are successfully synthesized, which exhibit simultaneously high CO₂ adsorption capacity of 17.6 wt % (4.0 mmol g^–1, 273 K/1.0 bar) and high adsorption selectivities of CO₂/N₂ (104) and CO₂/CH₄ (24). Especially, at the low pressure, e.g., 0.15 bar, the CO₂ uptake at 273 K can reach 8.7 wt % (1.97 mmol g^–1). The adsorption/selectivity properties are superior to most of microporous organic polymers (MOPs) reported in the literature. Besides the outstanding CO₂-capturing ability, the polymers also possess high uptakes of benzene and cyclohexane vapors up to 72.6 and 52.7 wt %, respectively. In addition, the effects of reaction activity and type of amino groups as well as the size and shape of building blocks on porous architecture of microporous polyaminals are studied. The disclosed results are helpful for the deep understanding of pore formation and interconnecting behavior in MOPs and therefore are of significant importance for the synthetic control of MOPs for a specific application in gas storage and capture of organic vapors

A ribbed strategy disrupts conventional metamaterial deformation mechanisms for superior energy absorption

Enhancing energy absorption in mechanical metamaterials has been a focal point in structural design. Traditional methods often include introducing heterogeneity across unit cells. Herein, we propose a straightforward ribbed strategy to achieve exceptional energy absorption. We demonstrate our concept through modified body-centered cubic (BCC) and face-centered cubic (FCC) ribbed truss-lattice metamaterials (BCCR and FCCR). Using stainless-steel 316L samples, compression tests indicate a 111% and 91% increase in specific energy absorption (SEA) for BCCR and FCCR, respectively, along with an enhancement in compression strength by 61.8% and 40.7%. Deformation mechanisms are comprehensively elucidated through both finite element analysis and theoretical calculations. The mitigation of stress concentration at nodes, redistribution of load transfer pathways within struts, and introduction of multiple plastic hinges collectively contribute to increased energy absorption and higher compression strength. Using rein-based polymer samples, the ribbed truss-lattice metamaterials also exhibit exceptional damage tolerance, experiencing only a 15% loss in maximum strength after cyclic compression at 20% strain, while maintaining a 73% higher SEA compared to their non-ribbed counterpart. This strategy extends beyond the discussed structures, presenting itself as a generic approach to enhance plateau strength and SEA.</p