Yan-Chao Zhao

Nitrogen-Containing Microporous Conjugated Polymers via Carbazole-Based Oxidative Coupling Polymerization: Preparation, Porosity, and Gas Uptake

Facile preparation of microporous conjugated polycarbazoles via carbazole-based oxidative coupling polymerization is reported. The process to form the polymer network has cost-effective advantages such as using a cheap catalyst, mild reaction conditions, and requiring a single monomer. Because no other functional groups such as halo groups, boric acid, and alkyne are required for coupling polymerization, properties derived from monomers are likely to be fully retained and structures of final polymers are easier to characterize. A series of microporous conjugated polycarbazoles (CPOP-2-7) with permanent porosity are synthesized using versatile carbazolyl-bearing 2D and 3D conjugated core structures with non-planar rigid conformation as building units. The Brunauer-Emmett-Teller specific surface area values for these porous materials vary between 510 and 1430 m(2) g(-1) . The dominant pore sizes of the polymers based on the different building blocks are located between 0.59 and 0.66 nm. Gas (H2 and CO2 ) adsorption isotherms show that CPOP-7 exhibits the best uptake capacity for hydrogen (1.51 wt% at 1.0 bar and 77 K) and carbon dioxide (13.2 wt% at 1.0 bar and 273 K) among the obtained polymers. Furthermore, its high CH4 /N2 and CO2 /N2 adsorption selectivity gives polymer CPOP-7 potential application in gas separation.

Preparation and characterization of triptycene-based microporous poly(benzimidazole) networks

We demonstrate the synthesis of two triptycene-based microporous poly(benzimidazole) networks through condensation of triptycene-hexone with dialdehyde in refluxing glacial acetic acid containing ammonium acetate. The benzimidazole-linkage in the resulting polymers is confirmed by Fourier transform infrared and solid-state 13C CP/MAS NMR spectroscopy. The spindle-shaped morphology of the obtained polymers was also observed through scanning electron microscopy. The materials, with Brunauer–Emmet–Teller (BET) specific surface area over 600 m2 g−1, possess a good hydrogen storage capacity (up to 1.57 wt% at 77 K and 1.0 bar) and a high carbon dioxide uptake (up to 14.0 wt% at 273 K and 1.0 bar). These excellent performances would probably make them promising candidates for gas-selective adsorption, heterogeneous catalysis, and proton-exchange membrane fuel cells.

Adsorption performance and catalytic activity of porous conjugated polyporphyrins via carbazole-based oxidative coupling polymerization

Carbazole-based oxidative coupling polymerization is an efficient method to prepare various porous polycarbazoles without requirement of any specific functional groups for coupling polymerization. Herein, facile preparation of porous conjugated polymers (CPOP-11 and CPOP-12) using porphyrin or Fe(II)–porphyrin as core structures through this approach is reported. The Brunauer–Emmett–Teller specific surface area of the obtained polymers is up to 1320 m2 g−1, which is comparable to metalloporphyrin based porous polymers prepared by other coupling polymerization methods. It is worth noting that the adsorption amount of toluene by CPOP-12 is high up to 1192 mg g−1 (about 13.0 mmol g−1) at its saturated vapor pressure, which would be very promising to eliminate harmful small aromatic molecules in the environment. As a kind of hydrophobic material, CPOP-11 could be more useful to extract methanol from water due to its high mass ratio of adsorbed methanol to water. Meanwhile, a porous polymer containing Fe(II)–porphyrin (CPOP-12) is also an effective catalyst for the formation of glycosyl sulfoxides from sulfides by promoting the transfer of oxygen atoms and can be reused without significant decrease in catalytic activity and amount of catalyst.

Facile Approach to Preparing Microporous Organic Polymers through Benzoin Condensation

A series of microporous organic networks linked by α-hydroxyl ketone were synthesized based on benzoin self-condensation of multiformyl-containing building blocks. Fourier transform infrared and solid-state (13)C CP/MAS NMR spectroscopy were utilized to confirm the α-hydroxyl ketone linkage of the obtained polymers. The hollow microspheric morphology can be observed from scanning electron microscopy and transmission electron microscopy images. The materials, with Brunauer-Emmet-Teller specific surface area up to 736 m(2) g(-1), possess a hydrogen storage capacity up to 1.42 wt % at 77 K and 1.0 bar and a carbon dioxide uptake up to 15.3 wt % at 273 K and 1.0 bar. These excellent characteristics would make them become promising candidates for gas storage.

Straightforward synthesis of a triazine-based porous carbon with high gas-uptake capacities

A triazine-based porous carbon material (TPC-1) was prepared directly from a fluorinated aromatic nitrile in molten zinc chloride. Trimerization of the nitrile and subsequent defluorination carbonization of the polymeric network result in the formation of TPC-1. The defluorination process is reversible and can etch the polymeric network to release CFn, thereby generating additional porosity and rendering TPC-1 a nitrogen-rich porous material. TPC-1 shows a high BET surface area of 1940 m2 g−1 and contains both micropores and mesopores, which facilitate the diffusion and adsorption of gas molecules. Gas adsorption experiments demonstrate outstanding uptake capacities of TPC-1 for CO2 (4.9 mmol g−1, 273 K and 1.0 bar), CH4 (3.9 mmol g−1, 273 K and 1.0 bar), and H2 (10.1 mmol g−1, 77 K and 1.0 bar). This straightforward synthesis procedure provides an alternative pathway to prepare high-performance porous carbon materials.

Microporous Organic Polymers with Ketal Linkages: Synthesis, Characterization, and Gas Sorption Properties

A series of microporous organic polymers with ketal linkages were synthesized based on the condensation of aromatic acetyl monomers with pentaerythritol. Fourier transform infrared and solid-state cross-polarization/magic-angle-spinning (13)C NMR spectroscopy were utilized to confirm the ketal linkages of the resulting polymers. The morphology can be observed from scanning electron microscopy and transmission electron microscopy images. The materials possess Brunauer-Emmet-Teller specific surface area values ranging from 520 to 950 m(2) g(-1), and the highest hydrogen sorption capacity is up to 1.96 wt % (77 K and 1.0 bar), which is superior to that of most of microporous organic polymers. The facile and cost-effective preparation process and excellent gas sorption properties make these kinds of materials promising candidates for practical applications.

Mannitol-based acetal-linked porous organic polymers for selective capture of carbon dioxide over methane

Four acetal-linked porous organic polymers (MAPOP-1–4) have been synthesized by the reaction of multi-aldehyde monomers and mannitol under solvothermal conditions without a template or a metal catalyst. Fourier transform infrared and solid-state 13C cross-polarization/magic-angle-spinning nuclear magnetic resonance spectroscopic measurements were utilized to confirm the structures of the obtained polymers. MAPOPs exhibit high physicochemical stability and a considerable Brunauer–Emmett–Teller specific surface area ranging from 310 to 920 m2 g−1. Owing to their microporous structures, together with their hydroxyl-rich skeletons, MAPOP-1–4 show high carbon dioxide adsorption capability (11.6–13.5 wt% at 273 K and 1.0 bar), heat of adsorption (29.0–31.6 kJ mol−1), and remarkable CO2/CH4 selectivity (8.1–11.6, IAST at 273 K and 1.0 bar). These performances of MAPOP-1–4 make them promising materials in the applications of small gas storage and selective capture.

Microporous spiro-centered poly(benzimidazole) networks: preparation, characterization, and gas sorption properties

Three microporous spiro-centered poly(benzimidazole) networks were synthesized based on the condensation of di-/trialdehyde with 3,3,3′,3′-tetramethyl-1,1′-spirobisindane-5,5′,6,6′-tetrone in refluxing glacial acetic acid containing ammonium acetate. Fourier transform infrared and solid-state cross-polarization/magic-angle-spinning 13C NMR spectroscopy techniques were utilized to confirm the presence of a benzimidazole ring in the obtained polymers. The morphology can be observed from scanning electron microscopy and transmission electron microscopy images. The materials possess a Brunauer–Emmet–Teller specific surface area ranging from 520 to 600 m2 g−1. The highest hydrogen and carbon dioxide sorption capacity values of the obtained poly(benzimidazole) networks are up to 1.60 wt% (77 K and 1.0 bar) and 13.6 wt% (273 K and 1.0 bar), respectively, which are comparable to those of most of the microporous organic polymers.

One-step solvothermal carbonization to microporous carbon materials derived from cyclodextrins

A series of cyclodextrin-based microporous carbon materials were synthesized through a facile one-step solvothermal carbonization process. The results of Fourier transform infrared and solid-state 13C CP/MAS nuclear magnetic resonance studies show that the obtained carbon materials contain a large amount of oxygen-containing functional groups, such as hydroxyl, carbonyl, and carboxyl groups. Spheres can be observed in the scanning electron microscopy and high resolution transmission electron microscopy images. These kinds of carbon materials possess Brunauer–Emmet–Teller specific surface area data ranging from 600 to 700 m2 g−1, which are much higher values than those of carbon materials obtained from hydrothermal carbonization processes. Furthermore, these materials show moderate sorption capabilities for hydrogen (up to 1.07 wt%, 77 K and 1.0 bar) and carbon dioxide (up to 12.7 wt%, 273 K and 1.0 bar). The excellent characteristic of these materials make them promising candidates for gas storage.

Novel approach to hydroxy-group-containing porous organic polymers from bisphenol A

We successfully employed bisphenol A and several different formyl-containing monomers as useful building blocks to construct a series of hydroxy-group-containing porous organic polymers in a sealed tube at high temperature. Fourier transform infrared and solid-state 13C CP/MAS NMR spectroscopy are utilized to characterize the possible structure of the obtained polymers. The highest Brunauer–Emmet–Teller specific surface area of the phenolic-resin porous organic polymers (PPOPs) is estimated to be 920 m2 g–1. The PPOPs exhibit a highest carbon dioxide uptake (up to 15.0 wt % (273 K) and 8.8 wt % (298 K) at 1.0 bar), and possess moderate hydrogen storage capacities ranging from 1.28 to 1.04 wt % (77 K) at 1.0 bar. Moreover, the highest uptake of methane for the PPOPs is measured as 4.3 wt % (273 K) at 1.0 bar.