Gas sorption and characterization of poly(ether‐b‐amide) segmented block copolymers

The solubilities of He, H₂, N₂, O₂, CO₂, CH₄, C₂H₆, C₃H₈, and n‐C₄H₁₀ were determined at 35°C and pressures up to 27 atmospheres in a systematic series of phase separated polyether–polyamide segmented block copolymers containing either poly(ethylene oxide) [PEO] or poly(tetramethylene oxide) [PTMEO] as the rubbery polyether phase and nylon 6 [PA6] or nylon 12 [PA12] as the hard polyamide phase. Sorption isotherms are linear for the least soluble gases (He, H₂, N₂, O₂, and CH₄), convex to the pressure axis for more soluble penetrants (CO₂, C₃H₈, and n‐C₄H₁₀) and slightly concave to the pressure axis for ethane. These polymers exhibit high CO₂/N₂ and CO₂/H₂ solubility selectivity. This property appears to derive mainly from high carbon dioxide solubility, which is ascribed to the strong affinity of the polar ether linkages for CO₂. As the amount of the polyether phase in the copolymers increases, gas solubility increases. The solubility of all gases is higher in polymers with less polar constituents, PTMEO and PA12, than in polymers with more polar PEO and PA6 units. CO₂/N₂ and CO₂/H₂ solubility selectivity, however, are higher in polymers with higher concentrations of polar repeat units. The sorption data are complemented with physical characterization (differential scanning calorimetry, elemental analysis, and wide angle X‐ray diffraction) of the various block copolymers. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2463–2475, 1999     

CO2 permeation properties of poly(ethylene oxide)-based segmented block copolymers

This paper discusses the gas permeation properties of poly(ethylene oxide) (PEO)-based segmented block copolymers containing monodisperse amide segments. These monodisperse segments give rise to a well phase-separated morphology, comprising a continuous PEO phase with dispersed crystallised amide segments. The influence of the polyether phase composition and of the temperature on the permeation properties of various gases (i.e., CO₂, N₂, He, CH₄, O₂ and H₂) as well as on the pure gas selectivities were studied in the temperature range of −5 °C to 75 °C. The CO₂ permeability increased strongly with PEO concentration, and this effect could partly be explained by the dispersed hard segment concentration and partly by the changing chain flexibility. By decreasing the PEO melting temperature the low temperature permeabilities were improved. The gas transport values were dependant on both the dispersed hard segment concentration and the polyether segment length (length between crosslinks). The gas selectivities were dependant on the polyether segment length and thus the chain flexibility.     

Synthesis and properties of poly(phenylacetylenes) having two polar groups or one cyclic polar group on the phenyl ring

Phenylacetylene (PA) derivatives having two polar groups (ester, 2a – d ; amide, 4) or one cyclic polar group (imide, 5a – c ) were polymerized using (nbd)Rh⁺[(η⁶‐C₆H₅)B^?(C₆H₅)₃] catalyst to afford high molecular weight polymers (～1 × 10⁶ – 4 × 10⁶). The hydrolysis of ester‐containing poly(PA), poly( 2a) , provided poly(3,4‐dicarboxyPA) [poly ( 3 )], which could not be obtained directly by the polymerization of the corresponding monomer. The solubility properties of the present polymers were different from those of poly(PA) having no polar group; that is, poly( 2a )–poly( 2d ) dissolved in ethyl acetate and poly( 4 ) dissolved in N,N‐dimethylformamide, while poly(PA) was insoluble in such solvents. Ester‐group‐containing polymers [poly( 2a )–poly( 2d )] afforded free‐standing membranes by casting from THF solutions. The membrane of poly( 2a ) showed high carbon dioxide permselectivity against nitrogen (PCO₂/PN₂ = 62). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5943–5953, 2006     

Effects of hard‐segment polymers on CO2/N2 gas‐separation properties of poly(ethylene oxide)‐segmented copolymers

Poly(ethylene oxide)‐segmented polyurethanes (PEO‐PUs) and polyamides (PEO‐PAs) were prepared, and their morphology and CO₂/N₂ separation properties were investigated in comparison with those of PEO‐segmented polyimides (PEO‐PIs). The contents of the hard and soft segments in the soft and hard domains, W_HS and W_SH, respectively, were estimated from glass‐transition temperatures with the Fox equation. The phase separation of the PEO domains depended on the kind of hard‐segment polymer; that is, W_HS was in the order PU > PA ≫ PI for a PEO block length (n) of 45–52. The larger W_HS of PUs and PAs was due to hydrogen bonding between the oxygen of PEO and the NH group of urethane or amide. The CO₂/N₂ separation properties depended on the kind of hard‐segment polymer. Compared with PEO‐PIs, PEO‐PUs and PEO‐PA had much smaller CO₂ permeabilities because of much smaller CO₂ diffusion coefficients and somewhat smaller CO₂ solubilities. PEO‐PUs also had a somewhat smaller permselectivity because of a smaller solubility selectivity. This was due to the larger W_HS of PEO‐PUs and PEO‐PAs, that is, a greater contamination of PEO domains with hard urethane and amide units. For PEO‐PIs, with a decrease in n to 23 and 9, W_HS became large and CO₂ permeability decreased significantly, but the permselectivity was still at a high level of more than 50 at 35 °C. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1707–1715, 2000     

Pebax‐Based Membrane Filled with Two‐Dimensional Mxene Nanosheets for Efficient CO2 Capture

Mixed matrix membranes (MMMs) made from inorganic fillers and polymers is a kind of promising candidate for gas separation. In this work, two‐dimensional MXene nanosheets were synthesized and incorporated into a polyether‐polyamide block copolymer (Pebax) matrix to fabricate MMM for CO₂ capture. The physicochemical properties of MXene nanosheets and MXene/Pebax membranes were studied systematically. The introduction of MXene nanosheets provided additional molecular transport channels and meanwhile enhanced the CO₂ adsorption capacity, thereby enhancing both the CO₂ peremance and CO₂/N₂ selectivity of Pebax membrane. The optimized MXene/Pebax membrane with a MXene loading of 0.15 wt % displayed a high separation performance with a CO₂ permeance of 21.6 GPU and a CO₂/N₂ selectivity of 72.5, showing potential application in CO₂ capture.     

Synthesis and properties of carbamate‐ and amine‐containing poly(phenylacetylenes)

The 3‐ and 4‐aminophenylacetylenes protected by t‐butoxycarbonyl (t‐Boc) and 9‐fluorenylmethoxycarbonyl (Fmoc) groups ( 3a – 6a ) were synthesized and polymerized using [(nbd)RhCl]₂ ( 1 ) and [(nbd)Rh⁺‐η⁶‐PhB^?Ph₃] ( 2 ) catalysts. The t‐Boc‐containing polymers [poly( 3a ) and poly( 4a )] were obtained in high yield (82–91%). Among the Fmoc‐protected monomers, the para‐derivative polymerized well [poly( 6a ); yield = 85–94%], whereas its meta‐substituted analogue did not afford high molecular weight polymer in good yield [poly( 5a ); yield = 10–15%]. The use of KN(SiMe₃)₂ as a cocatalyst in conjunction with 1 led to a dramatic increase in the molecular weight of the polymers. The acid‐ and base‐catalyzed removal of the t‐Boc and the Fmoc groups, respectively, generated primary amine‐containing polymers [poly( 3b )–poly( 6b )] which cannot be obtained directly by the polymerization of the corresponding monomers. The solubility characteristics of the polymers bearing protected amino groups were quite different from those of the unprotected ones, the former being soluble in polar solvents, whereas the latter displayed poor solubility even in polar protic or highly polar aprotic solvents. The attempts to accomplish the free‐standing membrane fabrication by solution casting were successful only for poly( 3a ), and an augmentation in the gas permeability and CO₂/N₂ permselectivity was discerned in comparison with the unsubstituted poly(phenylacetylene) and poly(m‐t‐butyldimethylsiloxyphenylacetylene). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1853–1863, 2009     

Above Room Temperature Organic Dielectric Switchable Material: Diprotonated 1,4‐Diazabicyclo[2.2.2]octane Shifts between Two Pyruvic Acids

A pure organic single crystal, [H₂dabco] · [PA]₂ ([H₂dabco]²⁺ = diprotonated 1,4‐diazabicyclo‐[2.2.2]octane, PA = pyruvic acid), was synthesized and its dielectric property was studied. [H₂dabco] · [PA]₂ owns a distinctive architecture composed of discrete hydrogen‐bonded trimeric units, of which one [H₂dabco]²⁺ cation bridged by two PA^– anions through N–H ··· O hydrogen bonding. The switchable property around 348 K was revealed by crystal structure studies between low and high dielectric states. In the high temperature phase, the [H₂dabco]²⁺ cation presents itself in a rotationally disordered state and lies at the symmetric center of the trimer. In the room temperature phase, it is frozen in an ordered state and shifts toward a PA^– anion at one end along the hydrogen bond.     

High‐Performance Polymers for Membrane CO2/N2 Separation

This Concept examines strategies to design advanced polymers with high CO₂ permeability and high CO₂/N₂ selectivity, which are the key to the success of membrane technology for CO₂ capture from fossil fuel‐fired power plants. Specifically, polymers with enhanced CO₂ solubility and thus CO₂/N₂ selectivity are designed by incorporating CO₂‐philic groups in polymers such as poly(ethylene oxide)‐containing polymers and poly(ionic liquids); polymers with enhanced CO₂ diffusivity and thus CO₂ permeability are designed with contorted rigid polymer chains to obtain high free volume, such as polymers with intrinsic microporosity and thermally rearranged polymers. The underlying rationales for materials design are discussed and polymers with promising CO₂/N₂ separation properties for CO₂ capture from flue gas are highlighted.     

Synthesis,characterization, and gas permeation properties of adamantane‐containing polymers of intrinsic microporosity

A new bis(catechol) monomer, namely, 4,4′‐((1r,3r)‐adamantane‐2,2‐diyl)bis(benzene‐1,2diol) (THADM) was synthesized by condensation of 2‐adamantanone with veratrole followed by demethylation of the formed (1r,3r)‐2,2‐bis(3,4 dimethoxyphenyl)adamantane. Polycondensation of THADM and various compositions of THADM and 5,5,6′,6′‐tetrahydroxy‐3,3,3′,3′‐tetramethylspirobisindane was performed with 2,3,5,6‐tetrafluoroterephthalonitrile (TFTPN) to obtain the homopolymer and copolymers. These polymers demonstrated good solubility in common organic solvents such as dichloromethane, chloroform, and tetrahydrofuran and could be cast into tough films from their chloroform solutions. GPC analysis revealed that number average molecular weights of polymers were in the range 48,100–61,700 g mol⁻¹, suggesting the formation of reasonably high molecular weight polymers. They possessed intrinsic microporosity with Brunauer‐Emmett‐Teller (BET) surface area in the range 703–741 m² g⁻¹. Thermogravimetric analysis of polymers indicated that 10% weight loss temperature was in the range 513–518 °C demonstrating their excellent thermal stability. THADM‐based polymer of intrinsic microporosity (PIM) showed P(CO₂) = 1080, P(O₂) = 232 and appreciable selectivity [α(CO₂/CH₄) = 22.6, α(CO₂/N₂) = 26.7, and α(O₂/N₂)= 5.7]. The gas permeability measurements revealed that with increase in the content of adamantane units in PIMs, selectivity increased and permeability decreased, following the trade‐off relationship. The gas separation properties of PIMs containing adamantane units were located close to 2008 Robeson upper bound for gas pairs such as CO₂/CH₄, CO₂/N₂, H₂/N₂, and O₂/N₂. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 16–24     

Novel high‐performance polymer memory devices containing (OMe)2tetraphenyl‐p‐phenylenediamine moieties

The functional polyimide (OMe)₂TPPA‐6FPI ( PI ) and the polyamide (OMe)₂TPPA‐6FPA ( PA ) consisting of electron‐donating N,N′‐bis(4‐aminophenyl)‐N,N′‐di(4‐methoxylphenyl)1,4‐phenylenediamine [(OMe)₂TPPA‐diamine] for memory application were prepared in this study. These polyimide and polyamide memory devices were fabricated with the sandwich configuration of indium tin oxide (ITO)/polymer/Al, and could be switched from the initial low‐conductivity (OFF) state to the high‐conductivity (ON) state with high ON/OFF current ratios of 10⁷ and 10⁹, respectively. PI exhibited dynamic random access memory (DRAM) performance, whereas PA showed static random access memory (SRAM) behavior. To get more insight into the memory behaviors of these two different types of polymer memory devices, molecular simulation on the basic unit was carried out. Furthermore, the differences of highest occupied molecular orbital (HOMO) energy level, lowest unoccupied molecular orbital (LUMO) charge density isosurfaces, dipole moment, and linkage conformation between PI and PA were found to affect the volatile memory behavior. Both polymer memory devices revealed excellent stability with long operation time of 10⁴ s at continuous applied voltage of ‐2 V. The effect of polymer thickness on the volatile memory behavior of PA was also investigated in this study. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

A Flexible Pro‐porous Coordination Polymer: Non‐conventional Synthesis and Separation Properties Towards CO2/CH4 Mixtures

The novel coordination polymers [Cu(Hoxonic)(H₂O)]_n ( 1 ) and [Cu(Hoxonic)(bpy)_0.5]_n ? 1.5 n H₂O ( 2?H₂O ) (H₃oxonic: 4,6‐dihydroxy‐1,3,5‐triazine‐2‐carboxylic acid; bpy: 4,4′‐bipyridine) have been isolated and structurally characterised by ab initio X‐ray powder diffraction. The dense phase 1 contains 1D zig‐zag chains in which Hoxonic dianions bridge square‐pyramidal copper(II) ions, apically coordinated by water molecules. On the contrary, 2?H₂O , prepared by solution and solventless methods, is based on 2D layers of octahedral copper(II) ions bridged by Hoxonic ligands, further pillared by bpy spacers. The resulting pro‐porous 3D network possesses small hydrated cavities. The reactivity, thermal, magnetic and adsorptive properties of these materials have been investigated. Notably, the adsorption studies on 2 show that this material possesses unusual adsorption behaviour. Indeed, guest uptake is facilitated by increasing the thermal energy of both the guest and the framework. Thus, neither N₂ at 77 K nor CO₂ at 195 K are incorporated, and CH₄ is only minimally adsorbed at 273 K and high pressures (0.5 mmol g^?1 at 2500 kPa). By contrast, CO₂ is readily incorporated at 273 K (up to 2.5 mmol g^?1 at 2500 kPa). The selectivity of 2 towards CO₂ over CH₄ has been investigated by means of variable‐temperature zero coverage adsorption experiments and measurement of breakthrough curves of CO₂/CH₄ mixtures. The results show the highly selective incorporation of CO₂ in 2 , which can be rationalised on the basis of the framework flexibility and polar nature of its voids.     

Two threefold interpenetrated two‐dimensional frameworks based on a flexible imidazole‐containing ligand and benzene‐1,4‐dicarboxylate

The open‐chain polyether‐bridged flexible ligand 1,2‐bis[2‐(1H‐1,3‐imidazol‐1‐ylmethyl)phenoxy]ethane (L) has been used to create two two‐dimensional coordination polymers under hydrothermal reaction of L with Cd^II or Co^II, in the presence of benzene‐1,4‐dicarboxylic acid (H₂bdc). In poly[[(μ₂‐benzene‐1,4‐dicarboxylato){μ‐1,2‐bis[2‐(1H‐1,3‐imidazol‐1‐ylmethyl)phenoxy]ethane}cadmium(II)] dihydrate], {[Cd(C₈H₄O₄)(C₂₂H₂₂N₄O₂)]·2H₂O}_n, (I), and the cobalt(II) analogue {[Co(C₈H₄O₄)(C₂₂H₂₂N₄O₂)]·2H₂O}_n, (II), the Cd^II and Co^II cations are six‐coordinated by four carboxylate O atoms from two different bdc²⁻ dianions in a chelating mode and two N atoms from two distinct L ligands. The metal ions, bdc²⁻ dianions and L ligands each sit across crystallographic twofold axes. The bdc²⁻ coordination mode and the coordinating orientation of the L ligand play an important role in constructing the novel two‐dimensional framework. Complexes (I) and (II) are threefold interpenetrated two‐dimensional frameworks; their structures are almost isomorphous, while the bond lengths, angles and hydrogen bonds are different in (I) and (II).     

N,N′‐Bis(Salicylidene)‐1,2‐Cyclohexanediamine Lanthanide(III) Coordination Polymers: Syntheses,Crystal Structures,and Luminescence Properties

The salen‐type ligand H₂L [H₂L = N,N′‐bis(salicylidene)‐1,2‐cyclohexanediamine] was utilized for the synthesis of two lanthanide(III) coordination polymers [LnH₂L(NO₃)₃MeOH]_n [Ln = Eu ( 1 ) and Ln = Lu ( 2 )]. The single‐crystal X‐ray diffraction analyses of 1 and 2 revealed that they are isomorphous and exhibit one‐dimension neutral structure, in which H₂L effectively functions as a bridging ligand and give rise to a chain‐like polymer. The luminescent properties of polymers in solid state and in solution were investigated and 1 exhibits typical red luminescence of Eu^III ions in solid state and dichloromethane solution and 2 emits the ligand‐centered blue luminescence. The energy transfer mechanisms in these luminescent lanthanide polymers were described through calculation of the lowest triplet level of ligand H₂L.     

One‐ and two‐dimensional CdII coordination polymers constructed from 2‐(2‐methyl‐1H‐benzimidazol‐1‐yl)acetate ligands

The one‐ and two‐dimensional polymorphic cadmium polycarboxylate coordination polymers, catena‐poly[bis[μ₂‐2‐(2‐methyl‐1H‐benzimidazol‐1‐yl)acetato‐κ³N³:O,O′]cadmium(II)], [Cd(C₁₀H₉N₂O₂)₂]_n, and poly[bis[μ₂‐2‐(2‐methyl‐1H‐benzimidazol‐1‐yl)acetato‐κ³N³:O,O′]cadmium(II)], also [Cd(C₁₀H₉N₂O₂)₂]_n, were prepared under solvothermal conditions. In each structure, each Cd^II atom is coordinated by four O atoms and two N atoms from four different ligands. In the former structure, two crystallographically independent Cd^II atoms are located on twofold symmetry axes and doubly bridged in a μ₂‐N:O,O′‐mode by the ligands into correspondingly independent chains that run in the [100] and [010] directions. Chains containing crystallographically related Cd^II atoms are linked into sheets viaπ–π stacking interactions. Sheets containing one of the distinct types of Cd^II atom are stacked perpendicular to [001] and alternate with sheets containing the other type of Cd^II atom. The second complex is a two‐dimensional homometallic Cd^II (4,4) net structure in which each Cd^II atom is singly bridged to four neighbouring Cd^II atoms by four ligands also acting in a μ₂‐N:O,O′‐mode. A square‐grid network results and the three‐dimensional supramolecular framework is completed by π–π stacking interactions between the aromatic ring systems.     

Synthesis and Characterization of New Block Copolymers with Poly(ethylene oxide) and Poly[3(S)‐sec‐butylmorpholine‐2,5‐dione] Sequences

Four different types of polydepsipeptide‐polyether block copolymers were synthesized via ring‐opening polymerization of 3(S)‐sec‐butylmorpholine‐2,5‐dione (BMD) in the presence of hydroxytelechelic poly(ethylene oxide) (PEO) with stannous octoate as a catalyst.The polymers were an AB block copolymer, an ABA block copolymer, an (A)₂B star shaped copolymer and an (A)₂B(A)₂ copolymer, where A is a poly[3(S)‐sec‐butylmorpholine‐2,5‐dione] (PBMD) and B a poly(ethylene oxide) block. The molar ratio of BMD to PEO was varied to obtain copolymers with different weight fractions of PBMD blocks ranging from 59.8 to 96.7 wt.‐%. The crystallinity of the PEO phase in the copolymers decreases in the following order: AB > (A)₂B > ABA > (A)₂B(A)₂ . The static contact angle θ decreases with increasing PEO content in the block copolymers.     

Polar hydrogen‐bonded organic chains in 4,4′‐bipyrazolium bromide and perchlorate monohydrates

4,4′‐Bipyrazolium [or 4‐(1H‐pyrazol‐4‐yl)pyrazolium] bromide monohydrate, C₆H₇N₄⁺·Br⁻·H₂O, and 4,4′‐bipyrazolium perchlorate monohydrate, C₆H₇N₄⁺·ClO₄⁻·H₂O, have closely related layered structures involving tight stacks of antiparallel N—H⋯N hydrogen‐bonded polar bipyrazolium chains [N⋯N = 2.712 (3) and 2.742 (2) Å], which are crosslinked by hydrogen bonds with water mol­ecules and counter‐anions.     

Trapping Dimethyltin Cations by Bipyridine‐N,N′‐Dioxide Ligands

N,N′‐dioxide ligands such as 2, 2′‐bipyridine‐N,N‐dioxide (BPDO‐I) and 4, 4′‐bipyridine‐N,N‐dioxide (BPDO‐II) were used to trap the hydrated dimethyltin cations under controlled hydrolysis. The use of the chelating ligand BPDO‐I leads to the isolation of the discrete monocation [Me₂Sn(BPDO‐I)(OH₂)(NO₃)]⁺[NO₃]^– ( 2 ), whereas the linear ligand BPDO‐II directs the construction of cationic polymers, [{Me₂Sn(OH₂)₂(μ‐BPDO‐II)}²⁺{NO₃^–}₂ · 2H₂O]_n ( 3· 2H₂O) and [{Me₂Sn(μ‐OH)(BPDO‐II)}₂²⁺{NO₃^–}₂ · H₂O]_n ( 4· H₂O) under different reaction conditions.     

Synthesis of double hydrophilic poly(ethylene oxide)‐b‐poly(2‐hydroxyethyl acrylate) by single‐electron transfer–living radical polymerization

In this study, the polymerization of (2‐hydroxyethyl) acrylate (HEA), in polar media, using Cu(0)‐mediated radical polymerization also called single‐electron transfer–living radical polymerization (SET‐LRP) is reported. The kinetics aspects of both the homopolymerization and the copolymerization from a poly(ethylene oxide) (PEO) macroinitiator were analyzed by ¹H NMR. The effects of both the ligand and the solvent were studied. The polymerization was shown to reach very high monomer conversions and to proceed in a well‐controlled fashion in the presence of tris[2‐(dimethylamino)ethyl]amine Me6‐TREN and N, N,N′, N″, N″‐pentamethyldiethylenetriamine (PMDETA) in dimethylsulfoxide (DMSO). SET‐LRP of HEA was also led in water, and it was shown to be faster than in DMSO. In pure water, Me₆‐TREN allowed a better control over the molar masses and polydispersity indices than PMDETA and TREN. Double hydrophilic PEO‐b‐PHEA block copolymers, exhibiting various PHEA block lengths up to 100 HEA units, were synthesized, in the same manner, from a bromide‐terminated PEO macroinitiator. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Four‐ and five‐coordinate copper(II) complexes with N‐(4,4‐diphenyl‐5‐oxo‐4,5‐dihydro‐1H‐imidazol‐2‐yl)glycine

The two title mononuclear compounds are four‐coordinate bis[N‐(5‐oxo‐4,4‐diphenyl‐4,5‐dihydro‐1H‐imidazolidin‐2‐ylidene)glycinato]copper(II) dimethylformamide disolvate, [Cu(C₁₇H₁₄N₃O₃)₂]·2C₃H₇NO, (I), and five‐coordinate aquabis[N‐(5‐oxo‐4,4‐diphenyl‐4,5‐dihydro‐1H‐imidazolidin‐2‐ylidene)glycinato]copper(II) dimethylformamide disolvate, [Cu(C₁₇H₁₄N₃O₃)₂(H₂O)]·2C₃H₇NO, (II). In (I), the Cu^II ion lies on an inversion centre with one‐half of the complex molecule in the asymmetric unit, while in (II) there are two independent ligand molecules in the asymmetric unit, with the Cu^II ion and coordinated water molecule located on a general position. In both crystal structures, the complex molecules assemble in ribbons via N—H...O hydrogen‐bond networks.     

Directing the Structural Features of N2‐Phobic Nanoporous Covalent Organic Polymers for CO2 Capture and Separation

A family of azo‐bridged covalent organic polymers (azo‐COPs) was synthesized through a catalyst‐free direct coupling of aromatic nitro and amine compounds under basic conditions. The azo‐COPs formed 3D nanoporous networks and exhibited surface areas up to 729.6 m² g^?1, with a CO₂‐uptake capacity as high as 2.55 mmol g^?1 at 273 K and 1 bar. Azo‐COPs showed remarkable CO₂/N₂ selectivities (95.6–165.2) at 298 K and 1 bar. Unlike any other porous material, CO₂/N₂ selectivities of azo‐COPs increase with rising temperature. It was found that azo‐COPs show less than expected affinity towards N₂ gas, thus making the framework “N₂‐phobic”, in relative terms. Our theoretical simulations indicate that the origin of this unusual behavior is associated with the larger entropic loss of N₂ gas molecules upon their interaction with azo‐groups. The effect of fused aromatic rings on the CO₂/N₂ selectivity in azo‐COPs is also demonstrated. Increasing the π‐surface area resulted in an increase in the CO₂‐philic nature of the framework, thus allowing us to reach a CO₂/N₂ selectivity value of 307.7 at 323 K and 1 bar, which is the highest value reported to date. Hence, it is possible to combine the concepts of “CO₂‐philicity” and “N₂‐phobicity” for efficient CO₂ capture and separation. Isosteric heats of CO₂ adsorption for azo‐COPs range from 24.8–32.1 kJ mol^?1 at ambient pressure. Azo‐COPs are stable up to 350 °C in air and boiling water for a week. A promising cis/trans isomerization of azo‐COPs for switchable porosity is also demonstrated, making way for a gated CO₂ uptake.