Graphene-Based Metal-Organic Framework Hybrids for Applications in Catalysis, Environmental, and Energy Technologies

Current energy and environmental challenges demand the development and design of multifunctional porous materials with tunable properties for catalysis, water purification, and energy conversion and storage. Because of their amenability to de novo reticular chemistry, metal-organic frameworks (MOFs) have become key materials in this area. However, their usefulness is often limited by low chemical stability, conductivity and inappropriate pore sizes. Conductive two-dimensional (2D) materials with robust structural skeletons and/or functionalized surfaces can form stabilizing interactions with MOF components, enabling the fabrication of MOF nanocomposites with tunable pore characteristics. Graphene and its functional derivatives are the largest class of 2D materials and possess remarkable compositional versatility, structural diversity, and controllable surface chemistry. Here, we critically review current knowledge concerning the growth, structure, and properties of graphene derivatives, MOFs, and their graphene@MOF composites as well as the associated structure-property-performance relationships. Synthetic strategies for preparing graphene@MOF composites and tuning their properties are also comprehensively reviewed together with their applications in gas storage/separation, water purification, catalysis (organo-, electro-, and photocatalysis), and electrochemical energy storage and conversion. Current challenges in the development of graphene@MOF hybrids and their practical applications are addressed, revealing areas for future investigation. We hope that this review will inspire further exploration of new graphene@MOF hybrids for energy, electronic, biomedical, and photocatalysis applications as well as studies on previously unreported properties of known hybrids to reveal potential "diamonds in the rough".

Preparation of hybrid cyanate ester resin in the presence of polysilazane and its properties

A hybrid cyanate ester resin containing polysilazane was prepared via the prepolymerization of bisphenol-A dicyanate ester monomer (BADCy) in the presence of polysilazane (PSZ) under low temperature conditions in a short period of time. Fourier transform-infrared (FT-IR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy reveal that the polymerization reaction of BADCy can be carried out in the presence of PSZ to obtain a hybrid resin below 100°C and polymethylsilazane (PHS) exhibits an improved prepolymerization effect when compared to polydimethylsilazane (PMS). FT-IR spectroscopy and gel permeation chromatography (GPC) showed that the prepolymerization degree of the PHS/BADCy resin increased upon increasing PHS mass fraction from 0 to 12 wt%, polymerization temperature from 60 to 100°C and polymerization time from 0 to 4 h. The PHS/BADCy hybrid resins samples were prepared and their process properties were investigated by rheometry and Differential scanning calorimetry (DSC). The results indicated that their viscosity was <10 Pa.s in the temperature range of 60–130°C, and the initial curing temperature and curing exothermic enthalpy were 121.9°C and 358.9 J/g, respectively. Furthermore, the cured PHS/BADCy resin possesses excellent thermal and mechanical properties, the 5% weight loss temperature (Td5) and glass transition temperature (Tg) were 424–441°C and 273–282°C, respectively. The cured PHS/BADCy resin with 4 wt% PHS showed the highest flexural strength of 146 MPa and flexural modulus of 4.1 GPa.

An in situ self-catalytic hybrid cyanate ester resin and its self-catalytic polymerization behavior

A novolac cyanate ester (NCE) with self-catalytic function that incorporates –Si–NH–CN group has been synthesized through the reaction between methylvinylcyclotrisilazane (MVSZ) and novolac cyanate ester (NCE).