Chunlong Kong

Polyethyleneimine Incorporated Metal-Organic Frameworks Adsorbent for Highly Selective CO2 Capture

A series of polyethyleneimine (PEI) incorporated MIL-101 adsorbents with different PEI loadings were reported for the first time in the present work. Although the surface area and pore volume of MIL-101 decreased significantly after loading PEI, all the resulting composites exhibited dramatically enhanced CO2 adsorption capacity at low pressures. At 100 wt% PEI loading, the CO2 adsorption capacity at 0.15 bar reached a very competitive value of 4.2 mmol g−1 at 25°C, and 3.4 mmol g−1 at 50°C. More importantly, the resulting adsorbents displayed rapid adsorption kinetics and ultrahigh selectivity for CO2 over N2 in the designed flue gas with 0.15 bar CO2 and 0.75 bar N2. The CO2 over N2 selectivity was up to 770 at 25°C, and 1200 at 50°C. We believe that the PEI based metal-organic frameworks is an attractive adsorbent for CO2 capture.

Direct synthesis of amine-functionalized MIL-101(Cr) nanoparticles and application for CO2 capture

A pure amine-functionalized MIL-101(Cr) has been synthesized for the first time by a simple method. The as-prepared nanoparticles are around 50 nm. In addition, the resulting amine-functionalized MIL-101(Cr) displayed excellent CO2 adsorption capacity, up to 15 mmol g−1 at 16 °C.

Remarkable CO2/CH4 selectivity and CO2 adsorption capacity exhibited by polyamine-decorated metal–organic framework adsorbents

Solid porous dual amine-decorated metal-organic framework (MOF) adsorbents with tunable porosity have been prepared. The adsorbents exhibit remarkable CO2/CH4 selectivity and CO2 adsorption capacity at low pressures.

A highly permeable mixed matrix membrane containing CAU-1-NH2 for H2 and CO2 separation.

A thin and compact mixed matrix membrane containing CAU-1-NH2 and the poly(methyl methacrylate) polymer has been originally synthesized. The as-prepared membrane exhibits high permeability of H2 and excellent H2/CO2 selectivity.

Enhanced selective CO2 adsorption on polyamine/MIL-101(Cr) composites

The global climate change induced by greenhouse gases has stimulated active research for developing efficient strategies to mitigate CO2 emission. In the present study, we prepared a series of polyamine/metal–organic framework (MOF) composites as highly selective CO2 adsorbents from a CO2/N2 mixture, which is relevant to CO2 capture in flue gas. We show that loading polyethyleneimine (PEI) into MIL-101(Cr) frameworks can significantly enhance the selective CO2 adsorption capacity at low pressure and ambient temperature. Further, the comparative study reveals that both the particle size of the MOF and the molecular-weight of PEI play an important role in the CO2 capture ability. Regarding the particle size, smaller MIL-101(Cr) particles can facilitate the loading of PEI into the inner pores and result in lower surface area/pore volume. Thus, the resulting PEI/MIL-101(Cr) composites possess lower CO2 adsorption capacity, but are compensated by higher selectivity of CO2 over N2. On the other hand, lower molecular-weight linear PEI could readily diffuse into the inner pores and effectively block the N2 adsorption. As a result, the as-prepared A-PEI-300 sample in this work exhibits an excellent CO2 uptake of 3.6 mmol g−1 and ultrahigh CO2/N2 selectivity at 0.15 bar and 25 °C. In contrast, the higher molecular-weight branched PEI is advantageous at elevated temperature, since the composites can retain high CO2 adsorption capacity owing to the large amount of primary amine groups. Overall, polyamine/MOF composites are shown to be good candidate adsorbents for CO2 capture from flue gas. To achieve the optimal CO2 capture ability, comprehensive optimization of the polyamine and MOF structures should be performed.

Amine-functionalized metal–organic frameworks: structure, synthesis and applications

We present a review on some recent studies on the syntheses, structures and properties of amine-functionalized metal–organic frameworks (MOFs), and highlight the benefits of amino functionality towards potential applications. Owing to the strong interaction between CO2 and basic amino functionalities, amine-functionalized MOFs have attracted much attention mainly for CO2 capture. Besides the most widely used in situ synthesis method, post-modification and physical impregnation methods are developed to prepare amine-functionalized MOFs with extremely high CO2 sorption capacity at low pressures. On the basis of the similar mechanism, amine-functionalized MOF-based membranes, including pure amine-functionalized MOF membranes and mixed matrix membranes, exhibit excellent CO2/H2, CO2/CH4 and CO2/N2 separation performance. Furthermore, amine-functionalized MOFs also demonstrate potential applications in catalysis.

A hollow ceramic fiber supported ZIF-8 membrane with enhanced gas separation performance prepared by hot dip-coating seeding

A hollow ceramic fiber supported ZIF-8 membrane has been prepared by a hot dip-coating seeding method followed by secondary growth. The obtained membrane exhibits excellent H2 permselectivity.

Sol-gel Auto-combustion Synthesis of Ni-CexZr1-xO2 Catalysts for Carbon Dioxide Reforming of Methane

Carbon dioxide reforming of methane (methane dry reforming) over Ni–Ce0.8Zr0.2O2 catalysts prepared by a sol–gel auto-combustion method and a conventional co-precipitation method were comparatively studied. We show that sol–gel auto-combustion is very promising for preparing thermal stable homogeneous mixed metal oxide catalysts. The auto-combustion synthesized catalyst exhibited higher initial activity and stability due to its smaller Ni crystalline size and intimate interaction between Ni and Ce0.8Zr0.2O2. In contrast, the co-precipitated catalyst showed poor activity and deactivated rapidly. The rapid deactivation was caused by a higher graphitization degree of the deposited carbon over co-precipitated catalyst with larger Ni crystalline size. We also found that the physico-chemical properties and catalytic activity of sol–gel auto-combustion synthesized catalysts were closely related to the metal nitrate (MN)/citric acid (CA) ratio. High MN/CA ratio led to more violent combustion behaviour and an accordingly higher degree of crystallization of the synthesized catalyst. In contrast, a low MN/CA ratio resulted in more carbon species residues and poor catalytic performance. The Ce/Zr ratio also had a profound influence on the phase structure, reducibility, oxygen vacancies and catalytic performance of Ni–Ce0.8Zr0.2O2 catalysts. Ni–Ce0.8Zr0.2O2 catalyst with cubic phase exhibited the best catalytic performance because of high reducibility, high Ni dispersion and strong Ni-CexZr1−xO2 interaction, and considerable amounts of oxygen vacancies.

Facile Synthesis of Aluminum-Based Metal–Organic Frameworks with Different Morphologies and Structures through an OH−-Assisted Method

We report the facile synthesis of aluminum-based metal-organic frameworks (MOFs) with different morphologies and structures by tuning the OH(-) content in the reaction solution. MIL-96 crystals with dodecahedral and hexagonal column shapes were successfully synthesized by tuning the OH(-) ion content of the synthesis solution. When the OH(-) ion content was further increased, MIL-110 with a nanorod morphology appeared as the product. For the first time, we obtained pure MIL-96 and MIL-110 under basic conditions directly by using the 1,3,5-benzenetricarboxylic acid (btc) linker. All samples show significant thermal stability, with a decomposition temperature above 300 °C. We found that the gas adsorption properties of MIL-96 were directly dominated by the crystal morphology. At 0.4 °C and 30 bar, the dodecahedral and hexagonal MIL-96 samples can adsorb 9.3 and 6.5 mmol g(-1) CO2, respectively, although they possess similar surface areas and identical crystalline structures. The MIL-110 nanorod shows a CO2 adsorption capacity of up to 16 mmol g(-1) under the same conditions.

Facile synthesis of MOFs with uncoordinated carboxyl groups for selective CO2 capture via postsynthetic covalent modification

A postsynthetic covalent strategy involving dual-acyl chloride has been developed to introduce uncoordinated carboxyl groups into amine containing metal–organic frameworks (MOFs). The carboxyl group functionalized MOFs have been characterized by various techniques, including X-ray diffraction patterning, scanning electron microscopy, Fourier transform infrared spectroscopy, nuclear magnetic resonance, thermal gravimetric analysis, and gas adsorption. Results clearly indicated uncoordinated carboxyl groups were successfully grafted to the MIL-101(Cr)–NH2 framework. In addition, most of the amine groups (>80%) were grafted with carboxyl groups, which indicates this method is very effective. The thermal stability and adsorption selectivity of CO2/N2 were substantially enhanced, albeit the BET surface areas and total pore volumes were reduced. These observations could be explained by the effect of elimination of macropores in the framework due to the projecting of new functional groups in pore apertures. Here the successful fabrication of a MOF with uncoordinated carboxyl groups provides the possibility of efficiently modifying other MOFs.