Considering practical applications, the thermal/thermal oxidative stability of fluorinated graphene should be given sufficient attention. Herein, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FT-IR) were used to investigate in detail the differences in the thermal stabilities of two types of fluorinated samples, fluorinated graphene (FG) and fluorinated porous graphene (FPG) with various fluorine contents, respectively, as well as the reasons for these differences. It was demonstrated that the thermal stability of FG and FPG was improved upon increasing the fluorine content, which was mainly caused by the enhancement of bond energy of the covalent C-F bonds. Moreover, compared to that of the raw graphene samples, the thermal oxidative stability of FG was reduced due to the defects brought by fluorination, while the thermal oxidative stability of FPG was improved, originating from the inflaming retarding effect of the fluorine element. Interestingly, the thermal oxidative stability of the fluorinated samples was even better than their thermal stability. Using a comparison of the two types of fluorinated samples and support from the computational simulations of the model molecules, it was suggested that a greater amount of CF (n = 2, 3) groups or defects in the FG samples resulted in its relatively worse thermal stabilities. Furthermore, electron paramagnetic resonance (EPR) spectroscopy was introduced to analyze the thermal stabilities of the fluorinated graphene samples as a novel method. The changes in the spin centers in samples after thermal treatment were studied, which indicated that the lower amount of the more stable spin centers of FPG was another reason leading to its more outstanding thermal stabilities in comparison to FG samples.

We report a multi-component synthetic strategy on a two-dimensional crystalline covalent organic framework (COF) by connecting acetonitrile with aromatic aldehyde and acetaldehyde moieties to form an unprecedented cyano-substituted buta-1,3-diene linkage. Different from most of the COFs that were crystallized from the condensations from two components, the presented COF is generated from two competitive and reversible reactions among three moieties. The buta-1,3-diene COF exhibits remarkable photoactivity with a low exciton binding energy of 44.4 ± 1.5 meV for promoted charge separation, which enables the buta-1,3-diene-linked COF as an efficient photocatalyst for various aerobic oxidation reactions under visible light. Our multi-component synthesis strategy may provide new sights for synthesizing COFs with structural diversity and functional variability that are hard to achieve by traditional COF synthesis.

Assembly of permanently porous metal-organic polyhedra/cages (MOPs) with bifunctional linkers leads to soft supramolecular networks featuring both porosity and processability. However, the amorphous nature of such soft materials complicates their...

Hypercrosslinked polymers (HCPs), amorphous microporous three-dimensional networks based on covalent linkage of organic building blocks, are a promising class of materials due to their high surface area and easy functionalization; however, this type of material lacks processability due to its network rigidity based on covalent crosslinking. Indeed, the development of strategies to improve its solution processability for broader applications remains challenging. Although HCPs have similar three-dimensionally crosslinked networks to polymer gels, HCPs usually do not form gels but insoluble powders. Herein, we report the synthesis of HCP gels from a thermally induced polymerization of a tetrahedral monomer, which undergoes consecutive solubilization, covalent bond formation, colloidal formation, followed by their aggregation and percolation to yield a hierarchically porous network. The resulting gels feature concentration-dependent hierarchical porosities and mechanical stiffness. Furthermore, these HCP gels can be used as a platform to achieve molecular-level hybridization with a two-dimensional polymer during the HCP gel formation. This method provides functional gels and corresponding aerogels with the enhancement of porosities and mechanical stiffness. Used in column-and membrane-based molecular separation systems, the hybrid gels exhibited a separation of water contaminants with the efficiency of 97.9 and 98.6% for methylene blue and KMnO 4 , respectively. This result demonstrated the potentials of the HCP gels and their hybrid derivatives in separation systems requiring macroscopic scaffolds with hierarchical porosity.

The attachment of fluorine to graphene is a facile means to activate the carbon bonds for subsequent covalent bonding to other molecules for the preparation of desired graphene derivatives. Therefore, an insight into the chemical reactivity of fluorinated graphene (FG) is very essential to enable precise control of the composition and structure of the final products. In this study, FG has been treated with various mass amounts of poly(oxypropylene)diamine (PEA) ranging from starvation to saturation to explore the dependence of a substitution reaction of diamines on the nature and location (attached onto the basal planes or along defects or edges) of C-F bonds. X-ray photoelectron spectroscopy directly tracked the atomic percentage of fluorine present and the carbon 1s bonding state, showing that the grafting ratio of diamines gradually increases with increased diamine mass ratio. The varying of the types and orientation of C-F bonds characterized by polarized attenuated total reflectance Fourier transform infrared spectroscopy indicates that "covalent" C-F bonds are more sensitive to the substitution reaction of diamines than ''semi-ionic'' C-F bonds, and the C-F bonds attached onto basal planes more preferably participate in the functionalization reaction of diamines than that of C-F bonded on non-coplanar regions (edges or defects). The one-dimensional expansion along the graphene c-axis shown by wide angle X-ray diffraction provides further evidence on the preferred functionalization reaction of C-F attached on the basal planes, resulting in a change of the average intersheet distance by various magnitudes.

Introduction of porosity into supramolecular gels endows soft materials with functionalities for molecular encapsulation, release, separation and conversion. Metalorganic polyhedra (MOPs), discrete coordination cages containing an internal cavity, have recently been employed as building blocks to construct polymeric gel networks with potential porosity. However, most of the materials can only be synthesized in organic solvents, and the examples of porous, MOP-based hydrogels are scarce. Here, we demonstrate the fabrication of porous hydrogels based on [Rh 2 (OHbdc) 2 ] 12 , a rhodium-based MOP containing hydroxyl groups on its periphery (OH-bdc = 5-hydroxy-1,3-benzenedicarboxylate). By simply deprotonating [Rh 2 (OH-bdc) 2 ] 12 with the base NaOH, the supramolecular polymerization between MOPs and organic linkers can be induced in the aqueous solution, leading to the kinetically controllable formation of hydrogels with hierarchical colloidal networks. When heating the deprotonated MOP, Na x [Rh 24 (O-bdc) x (OH-bdc) 24-x ], to induce gelation, the MOP was found to partially decompose, affecting the mechanical property of the resulting gels. By applying a post-synthetic deprotonation strategy, we show that the deprotonation degree of the MOP can be altered after the gel formation without serious decomposition of the MOPs. Gas sorption measurements confirmed the permanent porosity of the corresponding aerogels obtained from these MOP-based hydrogels, showing potentials for applications in gas sorption and catalysis.

A facile way to prepare fluorinated graphene (FG) with a high fluorine content and controllable structure is important to achieve its full potential application. In this work, it was found that the fluorine to carbon (F/C) ratio of fluorinated graphene oxide (FGO) was nearly twice as much as that of fluorinated chemically reduced graphene oxide (FCrGO) after fluorination at the same temperature. Concerning the detailed effects of oxygenic groups on the fluorination and structure of fluorinated graphene (FG), graphene oxides with different oxygen contents were fluorinated under the same conditions. It was shown that oxygenic groups promote the fluorination reaction by activating the surrounding aromatic regions and taking part in the substitution reaction with fluorine radicals, among which, hydroxyls and carbonyls tend to be replaced by fluorine atoms. Moreover, the fluorination mainly occurs at the edges and defects of graphene sheets with a low oxygen content, while the highly oxidized graphene sheets are fluorinated both at the edges and basal planes simultaneously. This indicates that the quantity and location of the C-F bonds in FGO can be controlled by adjusting the species and content of oxygenic groups in the precursor graphene oxide.

Honeycomb-like 2D π-conjugated conductive metal–organic framework gas sensors with channel sizes <2 nm and broad conductivity range are studied with low conductivity facilitating response, multi-porosity and short channel resulting in fast speed.