Chengcheng Tian

A Superacid-Catalyzed Synthesis of Porous Membranes Based on Triazine Frameworks for CO2 Separation

A general strategy for the synthesis of porous, fluorescent, triazine-framework-based membranes with intrinsic porosity through an aromatic nitrile trimerization reaction is presented. The essence of this strategy lies in the use of a superacid to catalyze the cross-linking reaction efficiently at a low temperature, allowing porous polymer membrane architectures to be facilely derived. With functionalized triazine units, the membrane exhibits an increased selectivity for membrane separation of CO(2) over N(2). The good ideal CO(2)/N(2) selectivity of 29 ± 2 was achieved with a CO(2) permeability of 518 ± 25 barrer. Through this general synthesis protocol, a new class of porous polymer membranes with tunable functionalities and porosities can be derived, significantly expanding the currently limited library of polymers with intrinsic microporosity for synthesizing functional membranes in separation, catalysis, and energy storage/conversion.

Efficient CO2 capture by a task-specific porous organic polymer bifunctionalized with carbazole and triazine groups

A porous triazine and carbazole bifunctionalized task-specific polymer has been synthesized via a facile Friedel-Crafts reaction. The resultant porous framework exhibits excellent CO2 uptake (18.0 wt%, 273 K and 1 bar) and good adsorption selectivity for CO2 over N2.

Template-Free Synthesis of Hierarchical Porous Metal-Organic Frameworks

A template-free synthesis of a hierarchical microporous-mesoporous metal-organic framework (MOF) of zinc(II) 2,5-dihydroxy-1,4-benzenedicarboxylate (Zn-MOF-74) is reported. The surface morphology and porosity of the bimodal materials can be modified by etching the pore walls with various synthesis solvents for different reaction times. This template-free strategy enables the preparation of stable frameworks with mesopores exceeding 15 nm, which was previously unattained in the synthesis of MOFs by the ligand-extension method.

Efficient CO2 Capture by Porous, Nitrogen‐Doped Carbonaceous Adsorbents Derived from Task‐Specific Ionic Liquids

The search for a better carbon dioxide (CO(2) ) capture material is attracting significant attention because of an increase in anthropogenic emissions. Porous materials are considered to be among the most promising candidates. A series of porous, nitrogen-doped carbons for CO(2) capture have been developed by using high-yield carbonization reactions from task-specific ionic liquid (TSIL) precursors. Owing to strong interactions between the CO(2) molecules and nitrogen-containing basic sites within the carbon framework, the porous nitrogen-doped compound derived from the carbonization of a TSIL at 500 °C, CN500, exhibits an exceptional CO(2) absorption capacity of 193 mg of CO(2) per g sorbent (4.39 mmol g(-1) at 0 °C and 1 bar), which demonstrates a significantly higher capacity than previously reported adsorbents. The application of TSILs as precursors for porous materials provides a new avenue for the development of improved materials for carbon capture.

In Situ Doping Strategy for the Preparation of Conjugated Triazine Frameworks Displaying Efficient CO2 Capture Performance

An in situ doping strategy has been developed for the generation of a novel family of hexaazatriphenylene-based conjugated triazine frameworks (CTFs) for efficient CO2 capture. The resulting task-specific materials exhibit an exceptionally high CO2 uptake capacity (up to 4.8 mmol g(-1) at 297 K and 1 bar). The synergistic effects of ultrananoporosity and rich N/O codoped CO2-philic sites bestow the framework with the highest CO2 adsorption capacity among known porous organic polymers (POPs). This innovative approach not only enables superior CO2 separation performance but also provides tunable control of surface features on POPs, thereby affording control over bulk material properties. We anticipate this novel strategy will facilitate new possibilities for the rational design and synthesis of nanoporous materials for carbon capture.

Synthesis of Porous, Nitrogen‐Doped Adsorption/Diffusion Carbonaceous Membranes for Efficient CO2 Separation

A porous, nitrogen-doped carbonaceous free-standing membrane (TFMT-550) is prepared by a facile template-free method using letrozole as an intermediate to a triazole-functionalized-triazine framework, followed by carbonization. Such adsorption/diffusion membranes exhibit good separation performance of CO2 over N2 and surpassing the most recent Robeson upper bound. An exceptional ideal CO2 /N2 permselectivity of 47.5 was achieved with a good CO2 permeability of 2.40 × 10(-13) mol m m(-2) s(-1) Pa(-1) . The latter results arise from the presence of micropores, narrow distribution of small mesopores and from the strong dipole-quadrupole interactions between the large quadrupole moment of CO2 molecules and the polar sites associated with N groups (e.g., triazine units) within the framework.

An efficient and reusable “hairy” particle acid catalyst for the synthesis of 5-hydroxymethylfurfural from dehydration of fructose in water

Poly(4-styrenesulfonic acid) brush-grafted silica particles, synthesized by surface-initiated atom transfer radical polymerization, were employed as a reusable acid catalyst for dehydration of fructose to 5-hydroxymethylfurfural (HMF) in water. The particles exhibited a high activity with the HMF yield of up to 31%, in contrast to 26% from the corresponding free homopolymer catalyst.

In Situ Coupling Strategy for the Preparation of FeCo Alloys and Co4N Hybrid for Highly Efficient Oxygen Evolution

An in situ coupling approach is developed to create a new highly efficient and durable cobalt-based electrocatalyst for the oxygen evolution reaction (OER). Using a novel cyclotetramerization, a task-specific bimetallic phthalocyanine-based nanoporous organic framework is successfully built as a precursor for the carbonization synthesis of a nonprecious OER electrocatalyst. The resultant material exhibits an excellent OER activity with a low overpotential of 280 mV at a current density of 10 mA cm-2 and high durability in an alkaline medium. This impressive result ranks among the best from known Co-based OER catalysts under the same conditions. The simultaneous installation of multiple diverse cobalt-based active sites, including FeCo alloys and Co4 N nanoparticles, plays a critical role in achieving this promising OER performance. This innovative approach not only enables high-performance OER activity to be achieved but simultaneously provides a means to control the surface features, thereby tuning the catalytic property of the material.

Three-Phase Catalytic System of H2O, Ionic Liquid, and VOPO4–SiO2 Solid Acid for Conversion of Fructose to 5-Hydroxymethylfurfural

Efficient transformation of biomass-derived feedstocks to chemicals and fuels remains a daunting challenge in utilizing biomass as alternatives to fossil resources. A three-phase catalytic system, consisting of an aqueous phase, a hydrophobic ionic-liquid phase, and a solid-acid catalyst phase of nanostructured vanadium phosphate and mesostructured cellular foam (VPO-MCF), is developed for efficient conversion of biomass-derived fructose to 5-hydroxymethylfurfural (HMF). HMF is a promising, versatile building block for production of value-added chemicals and transportation fuels. The essence of this three-phase system lies in enabling the isolation of the solid-acid catalyst from the aqueous phase and regulation of its local environment by using a hydrophobic ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM][Tf2N]). This system significantly inhibits the side reactions of HMF with H2O and leads to 91 mol % selectivity to HMF at 89 % of fructose conversion. The unique three-phase catalytic system opens up an alternative avenue for making solid-acid catalyst systems with controlled and locally regulated microenvironment near catalytically active sites by using a hydrophobic ionic liquid.

Pyrolysis of conjugated nanoporous polycarbazoles to mesoporous N-doped carbon nanotubes as efficient electrocatalysts for the oxygen reduction reaction

Developing new techniques for the synthesis of N-doped carbon nanotubes (N-CNTs) with high porosities and abundant N-doped active sites is significant for energy conversion and utilization. We report herein a novel non-CVD methodology that exploits a conjugated-nanoporous-polymer-driven, self-templated route toward a new family of highly N-doped carbon nanotubes. The utilization of a task-specific tubular nanoporous polycarbazole as a template maintains both high porosity and density of N-doped active sites, while simultaneously affording a hollow nanotube-like morphology of the final N-doped carbons. Attributed to these unique functionalities, the resultant N-CNT-based electrocatalyst exhibits a superior oxygen reduction reaction (ORR) activity with a half-wave potential of 0.88 V (vs. the reversible hydrogen electrode), higher long-term stability, and better methanol tolerance than commercial 20% Pt/C in alkaline media. More importantly, the ORR performance in an acidic medium exceeds that of the most previously reported non-precious carbonaceous catalysts. These findings could provide an alternative approach towards highly efficient non-precious N-CNT-based electrocatalysts for the ORR.