Heping Ma

Targeted synthesis of a porous aromatic framework with a high adsorption capacity for organic molecules

Tetrakis(4-bromophenyl)methane (TBPM) as a tetrahedral unit and a diboronic acid as a linker were selected to couple the phenyl rings into a porous aromatic framework, PAF-11. PAF-11 was polymerized via a Suzuki coupling reaction. A TG analysis showed that PAF-11 is thermally stable up to 400 °C in air. PAF-11 also has a high chemical stability and cannot be dissolved or decomposed in common solvents or concentrated hydrochloric acid. A N2 sorption measurement on activated PAF-11 revealed a surface area of 952 m2 g−1 in the Langmuir model. PAF-11 also shows a considerable adsorption capacity for H2. Interestingly, PAF-11 is a highly hydrophobic material but with a high methanol uptake (654 mg g−1 at saturated vapour pressure and room temperature). PAF-11 also exhibits high adsorption abilities for small aromatic molecules such as benzene and toluene (874 and 780 mg g−1, respectively, at saturated vapour pressure and room temperature) due to its aromatic framework. This ability of PAF-11 could be very useful to eliminate harmful small aromatic molecules produced by industry.

Synthesis of a porous aromatic framework for adsorbing organic pollutants application

Porous organic frameworks (POFs) have attracted considerable attention due to their high surface areas and good mechanical properties. A series of vivid characteristics in POFs, such as their plentiful phenyl rings texture, their high surface area, uniform pore size distribution and permanent porosity, make themselves suitable adsorbents to adsorb organic pollutants. To synthesize a new porous aromatic framework being composed of only phenyl rings, a monomer 1,3,5-tris(4-bromophenyl)benzene was employed. PAF-5 has been synthesized successfully using the Yamamoto-type Ullmann reaction. This material was characterized by Fourier transform infrared spectroscopy (FT-IR), 13C solid-state NMR, powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and N2 gas sorption. PAF-5 displaying high stability and high surface area exhibits excellent abilities to adsorb organic chemical pollutants at saturated vapour pressure and room temperature.

Highly Selective and Permeable Porous Organic Framework Membrane for CO2 Capture

DOI: 10.1002/adma.201400020 polymer; providing abundant active sites (e.g. amino groups) for CO 2 sorption. The obtained SNW-1 exhibits a three-dimensional framework with major pore size falling in the molecular scale (5 Å). Polysulfone (PSF Udel P-3500) is chosen as the appropriate matrix thanks to its glassy and organic nature, high thermal/chemical stability, and commercial availability. SNW-1/PSF membrane is fabricated by fi lling SNW-1 nanoparticles into PSF matrix using a spin-coating method; and further applied for CO 2 capture from gas streams of CO 2 /CH 4 and CO 2 /N 2 . The extended aminal network of SNW-1 polymer is built up by forming C-N bonds between two monomers of melamine and terephthalaldehyde, the structure of which (Figure 1 a) is verifi ed by 13 C and 15 N NMR data (Figure S1). [ 5 ] Upon polymerization, many pores are generated by an elimination of water molecules; and the porosity is probed by the N 2 -sorption measurement (Figure 1 b). The adsorption isotherms show a steep uptake at low relative pressures, followed by nearly horizontal adsorption and desorption branches at high pressures, typical for microporous materials. The texture data is summarized in Table S1, Supporting Information. The specifi c Brunauer– Emmet–Teller surface area (S BET ) and micropore volume are 821 m 2 g −1 and 0.26 cm 3 g −1 , indicating a high degree of cross linking of monomers; which is in an agreement of the peak disappearance of C O vibration (1690 cm −1 ) from aldehydes (Figure S2, Supporting Information). To be noted, the major pore size of voids in SNW-1 is calculated to be around 5 Å using the NL-DFT method as seen from the pore size distribution curve (insert picture in Figure 1 b); which can be also visualized in a molecular model of a fragment of SNW-1 in Figure 1 a. The value of pore size corresponds to a small micropore (3∼20 Å for microporous materials from IUPAC). IR spectrum shows that SNW-1 network bears free N-H groups (Figure S2, Supporting Information). Small pores and available N-H groups in this POF material are benefi cial for CO 2 recognition, and thus selective diffusion of CO 2 (3.3 Å) through the pores would be expected. The morphology and size of as-synthesized SNW-1 particles are studied by SEM ( Figure 2 a). Spherical shape is observed for as-prepared nanoparticles, and the size of an individual one is about 100 nm. Small particles are superior for obtaining a homogeneous mixture with matrix for further membrane fabrication, which is evidenced by a stable suspension without any visible sedimentation after one month at static condition (see insert picture in Figure 2 a). SNW-1/PSF membrane is fabricated by spin coating SNW-1/PSF suspension in CHCl 3 onto a macroporous glass frit. The optical picture in Figure 2 b shows that the support is entirely covered by SNW-1/PSF layer homogeneously. Insight views of the membrane layer are inspected by SEM. Figure 2 c and d display the side views of a particular Microporous membranes with pore openings at a molecular level can exhibit size selectivity as molecular sieves, which are promising in membrane-based gas separations. [ 1 ] Between microporous materials, zeolites, metal organic frameworks (MOFs) and active carbons are widely used for this purpose. Very recently, porous organic frameworks (POFs or COFs) [ 2 ] as a new family member of molecular sieves have been a hot and frontier research theme in materials science and technology, and attracted increasing attentions. POFs are composed of different organic moieties linked by covalent bonds, resulted in diversifi ed structures with controllable pores ranging from 0.3 to 50 nm. The features of highly permanent porosity, exceptionally high thermal stability, and low framework density; make this class of porous materials as an ideal candidate in membrane applications. [ 3 ] Microporous POFs owing to their high surface areas and intrinsic polymer characteristics of the entirely covalent bonded networks, possess great advantages over classical inorganic porous counterparts of being easily processed into membranes. Thus, the preparation of POF membranes for gas separation has been proposed [ 3b-d ] since they provide an energy-effi cient and reliable technology in separating various gases including air purifi cation, hydrogen recovery and the upgrading of natural gas. CO 2 capture or separation from the fl ue gas or natural gas is of great interests from the energy and environmental perspective. [ 4 ] Currently, removal or purifi cation of CO 2 from gas streams of power plants and reservoirs is commonly accomplished by cryogenic method or sorption approach using different adsorbents; both of which are costly and ineffi cient. In order to search an effi cient technology with long-term viability for CO 2 removal, microporous membranes have been pursued as alternative means because it combines two merits of high CO 2 uptake and affi nity in porous materials, and operation fl exibility with membrane process. Based on the considerations above, an N-rich Schiff based POF (SNW-1) [ 5 ] is selected as a potential candidate for membrane fabrication. SNW-1 constructed from industrial chemicals of melamine and di-aldehydes (the chemical structure of a fragment of SNW-1 is shown in Figure 1 a), is a nitrogen-rich

Novel lithium-loaded porous aromatic framework for efficient CO2 and H2 uptake

Novel porous aromatic frameworks, PAF-18-OH and its lithiated derivative PAF-18-OLi, have been successfully synthesized. In particular, PAF-18-OLi displays significant enhancement of H2 and CO2 adsorption capacity, especially for CO2 uptake (14.4 wt%). More valuably, the stable PAF-18-OLi material exhibits high CO2/N2 selectivity, as high as 129 in the case of CO2 capture from simulated post-combustion flue gas mixtures (85% N2 and 15% CO2). Furthermore, the PAF-18-OLi has shown improved H2 storage capacity after lithiation.

Post-metalation of porous aromatic frameworks for highly efficient carbon capture from CO2 + N2 and CH4 + N2 mixtures

The development of microporous materials for carbon capture, especially for carbon dioxide and methane, is a rapidly growing field based on the increasing demand for clean energy and pressing environmental concerns of global warming effected by greenhouse gases. To achieve this goal of developing carbon selective porous materials, a new porous aromatic framework featuring carboxyl-decorated pores, PAF-26-COOH, has been synthesized successfully. The modification of PAF-26 materials with representative light metals is exemplified by Li, Na, K and Mg via a post-metalation approach. The obtained PAF-26 products exhibit moderate surface area and controllable pore size at the atomic level. Gas sorption of CO2, CH4 and N2 is carried out on as-prepared PAF-26 samples at mild temperatures (273 K and 298 K). It is found that the PAF-26 materials show high adsorption capacity for CO2 and CH4 and low ability toward N2. Particularly, as-synthesized PAF-26 compounds exhibit remarkably high isosteric heats of adsorption toward CO2 and CH4, indicating high affinity for CO2 and CH4 gases. The gas selectivity for CO2–N2 and CH4–N2 mixtures is predicted by the IAST model. High selectivity of 80 for CO2 over N2 is obtained for PAF-26-COOMg. In addition, high selectivity values of CH4 over N2 are observed. The high performance including high storage capacity and selectivity makes PAF-26 materials promising for carbon capture or sequestration.

Novel Porphyrinic Porous Organic Frameworks for High Performance Separation of Small Hydrocarbons

A series of Porphyrinic-CTF materials are synthesized under ionothermal condition with high surface areas (>3200 m2/g) and tunable pore sizes. The ZnP-CTFs exhibit high adsorption capacities and selectivity towards C3H8, and C2H6 over CH4 as IAST prediction. Furthermore, we explore the utility of ZnP-CTF for gas chromatographic separation of the small hydrocarbons mixture based on their different van der waals interactions and polarizability. More importantly, the fast breakthrough test further proves that the ZnP-CTF-400 and ZnP-CTF-500 can separate the small hydrocarbons under kinetic dynamic conditions.

Synthesis of porous aromatic framework with tuning porosity via ionothermal reaction

PAF-16 which is based on tetrahedral units (TCPSi) and triangular building units, shows both high thermal stability and high chemical stability. The surface area of PAF-16 can be tuned by changing the reaction temperature and ratio of monomer and catalyst. PAF-16 also shows considerable adsorption capacity of CO(2).

A facile approach to prepare porphyrinic porous aromatic frameworks for small hydrocarbon separation

Porous organic frameworks (POFs) have attracted a great deal of attention thanks to their high surface areas, high stability and controllable skeletons. We synthesize a series of porphyrin-based porous aromatic frameworks (PAF-40s) through a cost-effective approach. The PAF-40s exhibit high surface areas and excellent chemical and thermal stability. Specifically, these PAF materials possess high adsorption capacity of small hydrocarbons, such as methane, ethylene, ethane and propane, at room temperature. Furthermore, the PAFs have remarkably high adsorption selectivity values of C2 and C3 hydrocarbons over CH4.

Self-Supported Fibrous Porous Aromatic Membranes for Efficient CO2/N2 Separations

In this paper, we describe a new synthesis protocol for the preparation of self-supported hollow fiber membranes composed of porous aromatic framework PAF-56P and PSF. PAF-56P was facilely prepared by the cross-coupling reaction of triangle-shaped cyanuric chloride and linear p-terophenyl monomers. The prepared PAF-56P material possesses an extended conjugated network, the structure of which is confirmed by nuclear magnetic resonance and infrared characterizations, as well as a permanent porosity with a BET surface area of 553.4 m(2) g(-1) and a pore size of 1.2 nm. PAF-56P was subsequently integrated with PSF matrix into PAF-56P/PSF asymmetric hollow fiber membranes via the dry jet-wet quench method employing PAF-56P/PSF suspensions. Scanning electron microscopy studies show that PAF-56P particles are embedded in the PSF matrix to form continuous membranes. Fabricated PAF-56P/PSF membranes were further exploited for CO2 capture, which was exemplified by gas separations of CO2/N2 mixtures. The PAF-56P/PSF membranes show a high selectivity of CO2 over N2 with a separation factor of 38.9 due to the abundant nitrogen groups in the PAF-56P framework. A preferred permeance for CO2 in the binary CO2/N2 gas mixture is obtained in the range of 93-141 GPU due to the large CO2 adsorption capacity and a large pore size of PAF-56P. Additionally, PAF-56P/PSF membranes exhibit excellent thermal and mechanical stabilities, which were examined by thermal analysis and gas separation tests with the dependencies of temperatures and pressures. The merits of high selectivity for CO2, good stability, and easy scale up make PAF-56P/PSF hollow fiber membranes of great interest for the industrial separations of CO2 from the gas exhausts.

Metal–Organic Frameworks Modulated by Doping Er3+ for Up-Conversion Luminescence

Here we present metal-organic frameworks prepared by a one-step synthesis method, possessing both architectural properties of MOF building and up-conversion luminescence of rare earth Er(3+) (hereafter denoted as Up-MOFs). Up-MOFs have characteristic up-conversion emissions at 520, 540, and 651 nm under the excitation of 980 nm owing to the multiple photon absorption. The up-conversion mechanism of these Up-MOFs has been discussed, and it can be attributed to the excited state absorption process. The design and synthesis of Up-MOF materials possessing near-infrared region excitation and up-conversion luminescence are fully expected to be candidates for the advancement of applications in bioimaging, sensors, optoelectronics, and energy conversion/storage devices.