Guipeng Yu

Liquid acid-catalysed fabrication of nanoporous 1,3,5-triazine frameworks with efficient and selective CO2 uptake

New classes of nanoporous organic polymers based on 1,3,5-triazine units (NOP-1–6) were synthesized via a straightforward, methane-sulfonic acid-catalysed, cost-effective Friedel–Crafts reaction of 2,4,6-trichloro-1,3,5-triazine and tetrahedral building blocks. Among them, NOP-3 with a Brunauer–Emmet–Teller (BET) specific surface area up to 894 m2 g−1 and the total volume exceeding 0.41 m3 g−1 exhibits good hydrogen adsorption capacity (up to 1.14 wt% at 77 K/1.0 bar) and high carbon dioxide uptake (up to 11.03 wt% at 273 K/1.0 bar). Furthermore, it presents an effective selectivity for CO2 adsorption (NOP-6, CO2/N2 selectivity 38.7 at 273 K/1.0 bar), demonstrating potential applications in gas adsorption and separation.

A rational construction of microporous imide-bridged covalent–organic polytriazines for high-enthalpy small gas absorption

A series of microporous imide functionalized 1,3,5-triazine frameworks (named TPIs@IC) were designed by an easy-construction technology other than the known imidization method for the construction of porous triazine-based polyimide networks (TPIs) with the same chemical compositions. In contrast to TPIs, TPIs@IC exhibit much higher Brunauer–Emmett–Teller (BET) surface areas (up to 1053 m2 g−1) and carbon dioxide uptake (up to 3.2 mmol g−1/14.2 wt% at 273 K/1 bar). The presence of abundant ultramicropores at 5.4–6.8 A, mainly ascribed to a high-level cyano cross-linking, allows the high heat absorption and high selective capture of CO2. The Qst (CO2 esoteric enthalpies) from their CO2 adsorption isotherms at 273 and 298 K are calculated to be in the range 46.1–49.3 kJ mol−1 at low CO2 loading, and the ideal CO2/N2 separation factors are up to 151, exceeding those of the most reported porous organic polymers to date. High storage capacities of TPIs@IC for other small gases like CH4 (5.01 wt% at 298 K/22 bar) and H2 (1.47 wt% at 77 K/1 bar) were also observed, making them promising adsorbents for gas adsorption and separation.

Tunable porosity of nanoporous organic polymers with hierarchical pores for enhanced CO2 capture

A series of cost-effective nanoporous organic polymers (NOP-50–NOP-52) with hierarchical pores for efficient CO2 capture were successfully synthesized via one-step Friedel–Crafts alkylation promoted by anhydrous FeCl3. Two chloromethyl monomers, i.e. dichloroxylene (DCX) and 4,4′-bis(chloromethyl)-1,1′-biphenyl (BCMBP) were utilized as crosslinkers to tailor the pore sizes. The porosity of the resultant polymers can be well-tuned by varying the length of crosslinkers and type of building blocks. More specifically, shorter linkers provide the polymers with greater microporosity, whereas longer linkers prove to block the microporosity created by the high-degree crosslinking of organic network. Introducing a series of highly rigid, nitrogen-containing, or metal-decorated building blocks features the obtained amorphous networks abundant microporosity and mesoporosity, and large Brunauer–Emmett–Teller (BET) surface areas up to 1650 m2 g−1 as measured by N2 adsorption at 77 K. Notably, such networks possess hierarchical pores with wide pore size distributions ranging from 0.55 to 4.3 nm. NOP-50A derived from DCX and carbazole exhibits competitive CO2 uptake up to 18.8 wt% at 273 K and 1 bar, surpassing most known HCPs. Remarkable selectivity ratios for CO2 adsorption over N2 (39–72) at 273 K and high CO2 isoteric heats of adsorption (34.2–46.7 kJ mol−1) were obtained. The high CO2/N2 selectivity and CO2 isosteric heat values could be ascribed to the good binding affinity of abundantly available electron-rich basic heteroatom or metal sites of the networks towards CO2. These results are significant for the construction of NOPs with hierarchical pores by introducing optimum building block and suitable length linkers for enhanced CO2 capture.

Facile Carbonization of Microporous Organic Polymers into Hierarchically Porous Carbons Targeted for Effective CO2 Uptake at Low Pressures

The advent of microporous organic polymers (MOPs) has delivered great potential in gas storage and separation (CCS). However, the presence of only micropores in these polymers often imposes diffusion limitations, which has resulted in the low utilization of MOPs in CCS. Herein, facile chemical activation of the single microporous organic polymers (MOPs) resulted in a series of hierarchically porous carbons with hierarchically meso-microporous structures and high CO2 uptake capacities at low pressures. The MOPs precursors (termed as MOP-7-10) with a simple narrow micropore structure obtained in this work possess moderate apparent BET surface areas ranging from 479 to 819 m(2) g(-1). By comparing different activating agents for the carbonization of these MOPs matrials, we found the optimized carbon matrials MOPs-C activated by KOH show unique hierarchically porous structures with a significant expansion of dominant pore size from micropores to mesopores, whereas their microporosity is also significantly improved, which was evidenced by a significant increase in the micropore volume (from 0.27 to 0.68 cm(3) g(-1)). This maybe related to the collapse and the structural rearrangement of the polymer farmeworks resulted from the activation of the activating agent KOH at high temperature. The as-made hierarchically porous carbons MOPs-C show an obvious increase in the BET surface area (from 819 to 1824 m(2) g(-1)). And the unique hierarchically porous structures of MOPs-C significantly contributed to the enhancement of the CO2 capture capacities, which are up to 214 mg g(-1) (at 273 K and 1 bar) and 52 mg g(-1) (at 273 K and 0.15 bar), superior to those of the most known MOPs and porous carbons. The high physicochemical stabilities and appropriate isosteric adsorption heats as well as high CO2/N2 ideal selectivities endow these hierarchically porous carbon materials great potential in gas sorption and separation.

A Luminescent Hypercrosslinked Conjugated Microporous Polymer for Efficient Removal and Detection of Mercury Ions

A hypercrosslinked conjugated microporous polymer (HCMP-1) with a robustly efficient absorption and highly specific sensitivity to mercury ions (Hg(2+)) is synthesized in a one-step Friedel-Crafts alkylation of cost-effective 2,4,6-trichloro-1,3,5-triazine and dibenzofuran in 1,2-dichloroethane. HCMP-1 has a moderate Brunauer-Emmett-Teller specific surface (432 m(2) g(-1)), but it displays a high adsorption affinity (604 mg g(-1)) and excellent trace efficiency for Hg(2+). The π-π* electronic transition among the aromatic heterocyclic rings endows HCMP-1 a strong fluorescent property and the fluorescence is obviously weakened after Hg(2+) uptake, which makes the hypercrosslinked conjugated microporous polymer a promising fluorescent probe for Hg(2+) detection, owning a super-high sensitivity (detection limit 5 × 10(-8) mol L(-1)).

BODIPY-based conjugated porous polymers for highly efficient volatile iodine capture

Capturing volatile radionuclide iodine from nuclear and medical waste streams is an important environmental issue. In this work, we found that the 2,6-position hydrogen atoms of a BODIPY core undergo fast iodination with volatile iodine at room temperature. Inspired by our observation, two novel BODIPY-based conjugated porous polymers (CPPs) BDP-CPP-1 and BDP-CPP-2, and the reference compound NBDP-CPP, were prepared, which were designed and then synthesized via the Sonogashira cross-coupling reaction of 1,3,5-triethynyl-benzene (TEB) and dibromo-substituted derivatives. With the coexistence of the BODIPY units and plenty of triple bonds and phenyl rings that could adsorb iodine with high capacity and affinity, compounds BDP-CPP-1 and BDP-CPP-2 exhibited satisfactory iodine adsorption capacities of 2830 mg g−1 and 2230 mg g−1, respectively. Moreover, BDP-CPP-1 was shown to adsorb volatile iodine through a chemical mechanism involving the 2,6-position hydrogen atoms of the BODIPY core. Surprisingly, the active sites on the BODIPY units for a chemical iodination reaction were mostly eliminated as a result of the crosslinking of BODIPY units during the Sonogashira coupling reaction. The preliminary results demonstrated that the iodine uptake abilities, which are in the order of BDP-CPP-1 > BDP-CPP-2 > NBDP-CPP, are not only dependent on the surface area, but also on the BODIPY units. The BDP-CPPs show high thermal stability with a decomposition temperature of about 300 °C. In addition, the BDP-CPPs demonstrated remarkable recyclability. Due to the highly π-conjugated porous structure along with the high affinity for iodine molecules and iodination sites, some BODIPY-based CPPs may provide a feasible pathway to adsorb other volatile compounds.

Metal Microporous Aromatic Polymers with Improved Performance for Small Gas Storage

A novel metal-doping strategy was developed for the construction of iron-decorated microporous aromatic polymers with high small-gas-uptake capacities. Cost-effective ferrocene-functionalized microporous aromatic polymers (FMAPs) were constructed by a one-step Friedel-Crafts reaction of ferrocene and s-triazine monomers. The introduction of ferrocene endows the microporous polymers with a regular and homogenous dispersion of iron, which avoids the slow reunion that is usually encountered in previously reported metal-doping procedures, permitting a strong interaction between the porous solid and guest gases. Compared to ferrocene-free analogues, FMAP-1, which has a moderate BET surface area, shows good gas-adsorption capabilities for H2 (1.75u2005wtu2009% at 77u2005K/1.0u2005bar), CH4 (5.5u2005wtu2009% at 298u2005K/25.0u2005bar), and CO2 (16.9u2005wtu2009% at 273u2005K/1.0u2005bar), as well as a remarkably high ideal adsorbed solution theory CO2 /N2 selectivity (107u2005v/v at 273u2005K/(0-1.0)u2005bar), and high isosteric heats of adsorption of H2 (16.9u2005kJu2009mol(-1) ) and CO2 (41.6u2005kJu2009mol(-1) ).

Phthalazinone structure-based covalent triazine frameworks and their gas adsorption and separation properties

In this work, new classes of phthalazinone-based covalent triazine frameworks (PHCTFs) were prepared by ionothermal synthesis from two full rigid dicyano building blocks with rigid, thermostable and asymmetric N-heterocycle-containing structures. The surface and internal morphologies of PHCTFs were examined by FE-SEM and TEM. The resultant microporous polymers, PHCTFs, exhibited BET specific surface areas up to 1845 m2 g−1 and a moderately narrow pore size distribution. According to the sorption measurements, the CO2 uptake can be up to 17.1 wt% (273 K/1 bar) and the H2 uptake can be up to 1.92 wt% (77 K/1 bar). Moreover, the initial slopes of the single component gas adsorption isotherms in the low pressure range were used as the gas separation ratios. The obtained polymer networks possess satisfactory CO2/N2 selectivity performance up to 52 and CO2/CH4 selectivity up to 12. Combining the relationship of the structure and performance, it can be concluded that a twisted and non-coplanar topology conformation can be used to improve the porosity of microporous organic polymers. At the same time, the nitrogen- and oxygen-rich characteristics of the phthalazinone core endow the networks with a strong affinity for CO2 and thereby high CO2 adsorption capacity. So the pore structure and chemical composition may play very important roles on the adsorption properties of small gas molecules.

Highly thermostable rigid-rod networks constructed from an unsymmetrical bisphthalonitrile bearing phthalazinone moieties

Phthalazinone rigid-rod networks with excellent thermostability have been prepared by the polyaddition of an unsymmetrical phthalonitrile-functional phthalazinone, namely 4-(4-(4-(3,4-dicyanophenoxy)phenyl)-1-oxophthalazin-2(1H)-yl)phthalonitrile (5) in the presence of promoting agents. 5 was readily prepared via nucleophilic displacement of 4-(4-hydroxylphenyl)(2H)-phthalazin-1-one (1) with 4-nitrophthalonitrile (3) under mild conditions. The substitution of N–H in phthalazinone was accomplished via a novel N–C coupling reaction in an essentially quantitative yield, confirmed by spectroscopic studies as well as a model reaction of 4-(4-tolyl)(2H)-phthalazin-1-one (2). Green prepolymers (7a–7c) were obtained by the polymerization of 5 in its melt phase with the charge of aromatic diamines (6a–6c), and with concurrent cyclization a mixture of poly(iminoisoindolenine) oligomers was produced. The obtained amorphous 7a–7c show Tgs ranging from 180 to 190 °C depending on the amine nature. Both 5 and 7a–7c have a non-coplanar conformation and exhibit sufficiently good solubility in common solvents (e.g., DMSO, DMF, DMAc, NMP, CHCl3, etc.), and hence can be processed either from their melt or from solution. The insoluble networks (8a–8c) prepared by direct curing of 5 or by post-curing of 7a–7c exhibit excellent thermal properties together with superior long-term thermo-oxidative stabilities.

Photovoltaic performance of long-chain poly(triphenylamine-phenothiazine) dyes with a tunable π-bridge for dye-sensitized solar cells

A set of conjugated polymers based on poly(triphenylamine-phenothiazine) with carboxylic acid side groups have been synthesized and utilized as sensitizers for dye-sensitized solar cells (DSSCs). The polymers feature a conjugated side-chain consisting of a thiophene unit (PPAT4), alternating with either 3,4-ethylenedioxythiophene (EDOT, PPAT5) or EDOT–thiophene (PPAT6) as the π-bridge. This methodology constitutes a consolidated step to adjust the molecular HOMO and LUMO energy levels of dyes, hence red-shifting and broadening the absorption spectra of a conjugated polymer. Compared with the model compound (PAT), the polymers exhibit a higher molar extinction coefficient throughout the visible region, and a better photovoltaic performance in DSSCs with I−/I3− electrolyte. Interestingly, depending on the Suzuki coupling reaction, we obtain a fairly high degree of polymerization (DP values are 58, 46, and 38 for PPAT4, PPAT5 and PPAT6, respectively) based on the three polymers. More encouraging is that when using the high DP polymers as sensitizers, photoelectrochemical tests based on the DSSC format demonstrate a power conversion efficiency of 4.7%, 3.7% and 4.1% for PPAT4, PPAT5 and PPAT6, respectively, under the illumination of AM1.5G and 100 mW cm−2. This presented a considerably high photo-to-electric conversion efficiency in polymer dye-sensitized solar cells, outperforming all polymer dye-sensitized solar cells previously reported.