Liangkui Zhu

Highly Mesoporous Single-Crystalline Zeolite Beta Synthesized Using a Nonsurfactant Cationic Polymer as a Dual-Function Template

Mesoporous zeolites are useful solid catalysts for conversion of bulky molecules because they offer fast mass transfer along with size and shape selectivity. We report here the successful synthesis of mesoporous aluminosilicate zeolite Beta from a commercial cationic polymer that acts as a dual-function template to generate zeolitic micropores and mesopores simultaneously. This is the first demonstration of a single nonsurfactant polymer acting as such a template. Using high-resolution electron microscopy and tomography, we discovered that the resulting material (Beta-MS) has abundant and highly interconnected mesopores. More importantly, we demonstrated using a three-dimensional electron diffraction technique that each Beta-MS particle is a single crystal, whereas most previously reported mesoporous zeolites are comprised of nanosized zeolitic grains with random orientations. The use of nonsurfactant templates is essential to gaining single-crystalline mesoporous zeolites. The single-crystalline nature endows Beta-MS with better hydrothermal stability compared with surfactant-derived mesoporous zeolite Beta. Beta-MS also exhibited remarkably higher catalytic activity than did conventional zeolite Beta in acid-catalyzed reactions involving large molecules.

Selective adsorption of carbon dioxide by carbonized porous aromatic framework (PAF)

A series of carbonized PAF-1s were obtained with enhanced gas storage capacities and isosteric heats of adsorption (Qst for short). Especially, PAF-1-450 can adsorb 4.5 mmol g−1 CO2 at 273 K and 1 bar. Moreover, it also exhibits excellent selectivity over other gases. On the basis of single component isotherm data, the dual-site Langmuir–Freundlich adsorption model-based ideal adsorption solution theory (IAST) prediction indicates that the CO2/N2 adsorption selectivity is as high as 209 at a 15/85 CO2/N2 ratio. Also, the CO2/CH4 adsorption selectivity is in the range of 7.8–9.8 at a 15/85 CO2/CH4 ratio at 0 < p < 40 bar, which is highly desirable for landfill gas separation. The calculated CO2/H2 adsorption selectivity is about 392 at 273 K and 1 bar for 20/80 CO2/H2 mixture. Besides, these carbonized PAF-1s possess excellent physicochemical stability. Practical applications in capture of CO2 lie well within the realm of possibility.

Porous ZnCo2O4 nanoparticles derived from a new mixed-metal organic framework for supercapacitors

Cobalt-based oxides have been shown to be promising materials for application in high-energy-density Li-ion batteries and supercapacitors. In this paper, we report a new and simple strategy for the synthesis of a mixed-metal spinel phase (ZnCo2O4) from a zinc and cobalt mixed-metal organic framework (JUC-155). It is important to rationally design a MOF with a precise ratio (Co/Zn) and a synthetic process that is simple and time saving. After solid-state annealing of the mixed-metal MOF precursor at 400 °C for two hours, a pure ZnCo2O4 phase with a high surface area (55 cm2 g−1) was obtained. When used as electrode materials for supercapacitors, an exceptionally high specific capacitance of 451 F g−1 was obtained at the scan rate of 5 mV s−1. The capacitance loss after 1500 cycles was only 2.1% at a current density of 2 A g−1, indicating that this phase has an excellent cycling stability. These remarkable electrochemical performances suggest that this phase is potentially promising for application as an efficient electrode in electrochemical capacitors.

Rational design and synthesis of NixCo3−xO4 nanoparticles derived from multivariate MOF-74 for supercapacitors

Mixed transition metal oxides have attracted much attention recently due to their potential application in energy and environmental sciences. The emergence of multivariate MOFs recently has attracted great research attention and provides an opportunity for multivariate mixed-metal oxides. In this work, five isostructural, single-phase MOF-74 structures with different divalent metals (MOF-74–Co, MOF-74–Ni, MOF-74–NiCo1, MOF-74–NiCo2 and MOF-74–NiCo4) were synthesised by varying the mole ratios of Ni/Co mixed-metal ions. After annealing at the appropriate temperature, Co3O4, NiO and three kinds of NixCo3−xO4 mixed-metal oxide nanoparticles with high surface area were easily obtained and the metal ratio was readily controlled, enabling us to systematically investigate the effect of different metal species amounts on the electrochemical properties of the mixed-metal oxide materials. When these metal oxides were used as electrode materials for supercapacitors, we found that the mixed-metal oxides NixCo3−xO4 obtained from bimetallic MOF-74–NiCo structures had obvious advantages compared with the monometallic oxides of MOF-74–Ni and MOF-74–Co. In particular, the NixCo3−xO4-1 with the Ni/Co metal ratio 1 : 1 exhibited the highest capacitance of 797 F g−1 and excellent cycling stability.

Direct observations of the MOF (UiO-66) structure by transmission electron microscopy

As a demonstration of ab initio structure characterizations of nano metal organic framework (MOF) crystals by high resolution transmission electron microscopy (HRTEM) and electron diffraction tomography methods, a Zr-MOF (UiO-66) structure was determined and further confirmed by Rietveld refinements of powder X-ray diffraction. HRTEM gave direct imaging of the channels.

ZIF-derived in situ nitrogen decorated porous carbons for CO2 capture

Various N-doped hierarchical porous carbons were prepared by using a new mixed-ligand ZIF (zeolitic imidazolate framework) (JUC-160) as the precursor in a one-step synthetic route without any additional carbon sources or purification steps. The effect of the ZIF precursor crystal size on the textural properties of the derived porous carbons was systematically studied. Microporosity was dominant in micron-sized JUC-160 crystal derived porous carbons, while more mesopore volume was present in porous carbons obtained from nanometre-sized JUC-160 crystals. The mJUC160-900 sample, which had a high nitrogen content and micropore volume, exhibited the highest CO2 uptake, which is 5.50 and 3.50 mmol g−1 at 273 and 298 K, respectively. Moreover, the analysis based on the ideal adsorbed solution theory (IAST) exhibited a high adsorption selectivity for CO2/N2 at 298 K and 1 bar (Sads = 29). Introduction to the international collaboration State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, at Jilin University China, has a long term cooperation with the Laboratory of Catalysis and Spectroscopy in Caen, at CNRS-France. Recently, Prof. Shilun Qius group and Prof. Valentin Valtchevs group had an international collaborative researching project entitled “Microporous materials: green synthesis for green applications”, which was supported by the National Natural Science Foundation of China (21261130584) and the French Science Foundation (ANR-12-IS08-0001-01). This project is focused on the design and synthesis of porous materials such as zeolites, metal organic frameworks (MOFs), covalent organic frameworks (COFs), porous aromatic frameworks (PAFs) and porous carbon materials that can find applications for clean energy storage, carbon capture, catalysis, and molecular selective sorption and separation.

Synthesis of chiral polymorph A-enriched zeolite Beta with an extremely concentrated fluoride route

Chiral zeolitic materials with intrinsically chiral frameworks are highly desired because they can combine both shape selectivity and enantioselectivity. In the field of zeolite, the synthesis of chiral polymorph A of zeolite Beta or chiral polymorph A-enriched zeolite Beta is one of the biggest challenges. We demonstrate here a generalized extremely concentrated fluoride route for the synthesis of chiral polymorph A-enriched zeolite Beta in the presence of five achiral organic structure-directing agents. The polymorph A-enriched Ti-Beta shows a higher enantioselectivity for the asymmetric epoxidation of alkenes than the normal Ti-Beta.

Design and synthesis of high performance LiFePO4/C nanomaterials for lithium ion batteries assisted by a facile H+/Li+ ion exchange reaction

The main objective of this work is to determine a novel and universal method for the lithiation of amorphous hydrated FePO4, typically a nanoscale FePO4/polyaniline composite, by a facile H+/Li+ ion exchange reaction proceeding in a nonaqueous medium that was rigorously deduced and studied with the help of several chemical/physical analytical techniques. The resulting Li-derivative is proved to be a desirable precursor for fabricating LiFePO4/C nanomaterials with ideal structural features containing highly crystalline LiFePO4 nanoparticles completely coated with N-doped conductive carbon. More importantly, the LiFePO4/C nanomaterial is capable of offering excellent rate capability and appealing cyclability that was strongly supported by the results of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) tests.

An elaborate structure investigation of the chiral polymorph A-enriched zeolite beta

Polymorph A-enriched zeolite beta was hydrothermally synthesized from an extremely concentrated system using tetraethylammonium hydroxide (TEAOH) as an organic structure-directing agent (OSDA) in the presence of fluoride. The sample was investigated by powder X-ray diffraction (XRD), 29Si magic angle spinning nuclear magnetic resonance (MAS NMR), 19F MAS NMR, and high-resolution transmission electron microscopy (HRTEM). The polymorph A enrichment was confirmed by the characterization, and the percentage of polymorph A was determined to be approximately 66% by DIFFaX simulation and HRTEM analyses. A pure polymorph A stacking area was detected by HRTEM, and the chiral structure of polymorph A in the zeolite beta was investigated on the basis of the HRTEM images.

N-Methyl-2-pyrrolidone assisted synthesis of hierarchical ZSM-5 with house-of-cards-like structure

Development of facile, economic and green routes towards the synthesis of hierarchical zeolites with high catalytic activity still remains a challenge in modern industrial catalysis. In this paper, we report on a novel synthesis of house-of-cards-like ZSM-5 (HCL-ZSM-5) via the introduction of N-methyl-2-pyrrolidone into a template-free zeolite synthesis system. Importantly, the HCL-ZSM-5 presents much better catalytic performances in the cracking of cumene and 1,3,5-triisopropylbenzene (TIPB) than conventional porous catalysts (ZSM-5, Y zeolite and Al-MCM-41).