Rizhi Chen

Bio: Rizhi Chen is an academic researcher from Nanjing Tech University. The author has contributed to research in topics: Catalysis & Ceramic membrane. The author has an hindex of 27, co-authored 119 publications receiving 2506 citations. Previous affiliations of Rizhi Chen include Monash University, Clayton campus.

Synthesis of p-aminophenol from p-nitrophenol over nano-sized nickel catalysts

Abstract: p-Aminophenol was synthesized by catalytic hydrogenation of p-nitrophenol on nano-sized nickel catalysts prepared by a chemical reduction method from aqueous solutions. The catalysts were characterized by XRD, EDS, SEM, HRTEM and Mastersizer 2000. Analysis results show that as-prepared catalysts are pure f.c.c. nickel and are prone to aggregation; the average particle size of nickel catalysts is 57 nm and there are high-density defects on particle surfaces. In hydrogenation reactions of p-nitrophenol, the hydrogenation rate is zero-order dependent on nitro aromatics and increases with increasing of hydrogen pressure. Compared with commercial Raney Ni, catalytic properties (activity, selectivity, and stability) of the as-prepared nickel are superior. The reason proposed for higher catalytic activity of nano-sized nickel is a combination effect of the small particle size and high-density surface defects. The partial sintering of nano-sized nickel might lead to the deactivation of the catalytic activity of nano-sized nickel.

High-yield synthesis of zeolitic imidazolate frameworks from stoichiometric metal and ligand precursor aqueous solutions at room temperature

Abstract: Zeolitic imidazolate frameworks ZIF-8 and ZIF-67 were prepared from stoichiometric metal and ligand aqueous solutions at room temperature within 10 min. Triblock copolymer and ammonium hydroxide are both essential for the formation of ZIFs. Ammonium hydroxide in the aqueous solution deprotonates 2-methylimidazole, and the PEO groups of the triblock copolymer surfactant electrostatically attract metal ions, leading to the formation of ZIF-8 and ZIF-67. The ZIF-8 yield is more than 98%, which is the highest so far. This method is very promising for efficient and environmentally friendly synthesis of ZIFs for practical applications.

Oriented two-dimensional zeolitic imidazolate framework-L membranes and their gas permeation properties

Abstract: A two-dimensional zeolitic imidazolate framework (ZIF), ZIF-L, with a unique anisotropic pore system makes it an excellent material for investigating ZIF membranes with crystallographically preferred orientation and their effects on gas separation properties. A b-oriented ZIF-L membrane was successfully prepared from a randomly oriented seed layer. In contrast, a c-oriented ZIF-L crystal layer was attached to a support through vacuum filtration in the presence of polyethyleneimine. After a short-time secondary growth, the oriented layer grew into a continuous membrane with a high degree of c-out-of-plane orientation. Gas separation studies demonstrated the orientation-dependent separation behavior. In single gas permeation experiments, the c-oriented ZIF-L membrane has higher ideal selectivities of 8.1 for H2/N2 and 24.3 for H2/CO2 compared to the corresponding values of 3.9 and 5.5 for the b-oriented ZIF-L membrane. The results of binary gas permeation showed decreased separation factors of the c-oriented membrane, but were still much higher than those of the b-oriented membrane. This work provides new insights into controlling ZIF membrane orientation for achieving desirable gas separation performance.

Metal–organic frameworks meet metal nanoparticles: synergistic effect for enhanced catalysis

Abstract: Metal–organic frameworks (MOFs), established as a relatively new class of crystalline porous materials with high surface area, structural diversity, and tailorability, attract extensive interest and exhibit a variety of applications, especially in catalysis. Their permanent porosity enables their inherent superiority in confining guest species, particularly small metal nanoparticles (MNPs), for improved catalytic performance and/or the expansion of reaction scope. This is a rapidly developing interdisciplinary research field. In this review, we provide an overview of significant progress in the development of MNP/MOF composites, including various preparation strategies and characterization methods as well as catalytic applications. Special emphasis is placed on synergistic effects between the two components that result in an enhanced performance in heterogeneous catalysis. Finally, the prospects of MNP/MOF composites in catalysis and remaining issues in this field have been indicated.

State of the Art and Prospects in Metal-Organic Framework (MOF)-Based and MOF-Derived Nanocatalysis.

Abstract: Metal-organic framework (MOF) nanoparticles, also called porous coordination polymers, are a major part of nanomaterials science, and their role in catalysis is becoming central. The extraordinary variability and richness of their structures afford engineering synergies between the metal nodes, functional linkers, encapsulated substrates, or nanoparticles for multiple and selective heterogeneous interactions and activations in these MOF-based nanocatalysts. Pyrolysis of MOF-nanoparticle composites forms highly porous N- or P-doped graphitized MOF-derived nanomaterials that are increasingly used as efficient catalysts especially in electro- and photocatalysis. This review first briefly summarizes this background of MOF nanoparticle catalysis and then comprehensively reviews the fast-growing literature reported during the last years. The major parts are catalysis of organic and molecular reactions, electrocatalysis, photocatalysis, and views of prospects. Major challenges of our society are addressed using these well-defined heterogeneous catalysts in the fields of synthesis, energy, and environment. In spite of the many achievements, enormous progress is still necessary to improve our understanding of the processes involved beyond the proof-of-concept, particularly for selective methane oxidation, hydrogen production, water splitting, CO2 reduction to methanol, nitrogen fixation, and water depollution.

Dialkylbiaryl phosphines in Pd-catalyzed amination: a user's guide

Abstract: Dialkylbiaryl phosphines are a valuable class of ligand for Pd-catalyzed amination reactions and have been applied in a range of contexts. This perspective attempts to aid the reader in the selection of the best choice of reaction conditions and ligand of this class for the most commonly encountered and practically important substrate combinations.

Photochemical green synthesis of calcium-alginate-stabilized Ag and Au nanoparticles and their catalytic application to 4-nitrophenol reduction.

Abstract: Silver and gold nanoparticles have been grown on calcium alginate gel beads using a green photochemical approach. The gel served as both a reductant and a stabilizer. The nanoparticles were characterized using UV−visible spectroscopy, X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), energy dispersive X-ray (EDS), and selected area electron diffraction (SAED) analyses. The particles are spherical, crystalline, and the size ranges for both Ag and Au nanoparticles are <10 nm. It is noticed from the sorption experiment that the loading of gold on calcium alginate beads is much more compared to that of Ag. The effectiveness of the as-prepared dried alginate-stabilized Ag and Au nanoparticles as a solid phase heterogeneous catalyst has been evaluated, for the first time, on the well-known 4-nitrophenol (4-NP) reduction to 4-aminophenol (4-AP) in the presence of excess borohydride. The reduction was very efficient and followed zero-order kinetics for both Ag and Au nanocompos...