Wavenumber /cm as-prepared MA-in as-prepared MA-i-c as-prepared MAn as-prepared MAc as-prepared MAc -n 1095

Novel nitrogen‐containing mesoporous carbon with well‐ordered pores (NMC‐G) and high basicity is synthesized using a low‐cost single‐molecule precursor, gelatin biomolecule, and SBA‐15 as a template via nanocasting method. The obtained materials are thoroughly characterized. It is found that the prepared materials have excellent textural properties such as high specific surface areas, huge pore volumes, and large pore diameters. The pore diameter of the materials can also be controlled with a simple adjustment of the pore diameter of the hard templates. The C/N ratio of the samples is calculated to be ≈6.01, which is slightly higher than that observed for mesoporous carbon nitride samples. X‐ray photoelectron spectroscopy (XPS) reveals the presence of sp2 hybridized carbon in aromatic ring structure attached to amino groups. The materials could adsorb a huge quantity of CO2. The sensing capability of the materials with different pore diameters for different adsorbates including ethanol, acetic acid, aniline, toluene, and ammonia is also investigated. Among the materials with different pore diameters studied, the material with the highest basicity and the largest pore diameter (NMC‐G‐150) showed excellent sensing performance with a high selectivity of adsorption for acetic acid molecule.

Highly ordered mesoporous carbon nitride (CN) with an extremely high nitrogen content and tunable pore diameters was synthesized by using a new precursor with a high nitrogen content, aminoguanidine hydrochloride and mesoporous silica SBA-15 with different pore diameters as hard templates. Surprisingly, the N/C ratio of the prepared mesoporous CN (MCN-4: 1.80) was considerably higher than that of the theoretically predicted C(3)N(4) nanostructures (1.33). This is mainly due to the fact that the CN precursor easily undergoes polymerization at high temperature and affords a highly stable polymer composed of a diamino-s-tetrazine moiety with a six-membered aromatic ring containing six nitrogen atoms that are linked trigonally with the nitrogen atoms. The obtained materials were thoroughly characterized by means of XRD, nitrogen adsorption, high resolution TEM, electron energy loss spectra, high resolution SEM, X-ray photoelectron spectroscopy, FTIR, and C, N, O, and S analysis. The results show that the MCN-4 materials possess a well-ordered mesoporous structure similar to SBA-15 with a high specific surface area and tunable band gap in the range of 2.25-2.49 eV. Interestingly, the pore diameter of the materials can be finely tuned from 3.1-5.8 nm by increasing the pore diameter of the hard-template SBA-15. The reaction temperature plays a critical role for the formation of MCN, and we found that 400 °C is the best condition to obtain MCN-4 with a high nitrogen content. We have further investigated the catalytic application of the MCN-4 materials towards Friedel-Crafts hexanoylation of benzene and compared the results with the mesoporous CN with less nitrogen content (MCN-1) and nonporous CN. Among the materials studied, MCN-4 showed the highest activity, affording a high yield of hexanophenone within a few hours, which is mainly due to the presence of free amine groups on the wall structure of MCN-4.

Here we demonstrate a facile synthesis of 3D mesoporous carbon nitride with Ia3d symmetry (MCN-6) using mesoporous silica KIT-6 with 3D porous structure and different pore diameters as hard templates, and ethylenediamine and carbon tetrachloride as the sources for N and C, and C, respectively. The obtained materials possess bimodal pores that can be controlled with a simple adjustment of the pore diameter of the KIT-6 templates. The lower angle powder X-ray diffraction (XRD) patterns and high resolution transmission electron microscope (HRTEM) images confirm that the MCN-6 materials possess a well-ordered mesoporous 3D structure with a highly interwoven and a branched pore structure. The textural parameters such as the specific surface areas and specific pore volumes of the materials can also be controlled by tuning the pore diameter of the hard template. The specific surface area and the specific pore volume of the samples increase with increasing the pore diameter of the hard template. The C/N ratio of the MCN-6 is ca. 4.3 which is similar to that obtained for MCN-1 prepared from SBA-15 as template. FT-IR and XPS spectroscopy results reveal that samples contain a CN network with a lot of free NH 2 groups which are originated from ethylenediamine and can offer the basic sites. The temperature programmed desorption of CO 2 confirms that the samples are highly basic and the basicity of the sample is 0.195 mmol of CO 2 per g which is higher than that of MCN-1 (0.14 mmol of CO 2 per g). We tested the performance of MCN-6 materials in the base-catalyzed Knoevenagel condensation of benzaldehyde and malononitrile. The catalysts exhibit excellent activity and afford a high yield of the corresponding a,b-unsaturated nitrile in a short reaction time even at room temperature. In addition, catalysts are highly stable and can be recyclable several times without affecting their activity.

No abstract

Copper-ion-exchanged SSZ-13 has been demonstrated to be an effective catalyst for the ammonia selective catalytic reduction of NO x . However, the Cu-SSZ-13 is still susceptible to hydrothermal degradation, which reduces the catalyst lifetime. We herein report that the hydrothermal stability of Cu-SSZ-13 can be remarkably enhanced through loading with a small amount of cerium. To clearly reveal the enhancement effect of cerium, we focused on an aluminum-rich Cu-SSZ-13 zeolite (Si/Al ratio: 6.5) with copper loadings ranging from ca. 3.4% to 4.1%, which was found to give high hydrothermal stability while still suffering from considerable degradation upon severe hydrothermal aging. Different cerium loadings were investigated, and a cerium loading with a limited range of ca. 0.2–0.4 wt % resulted in the best enhancement. The introduction of only a small amount of cerium was beneficial because it enabled a high copper loading and abundant Brønsted acidity sites that are needed for high SCR activities over a broad temperature range. Various characterization methods, including Rietveld refinement, transmission electron microscopy with energy-dispersive X-ray spectroscopy, scanning electron microscopy, and electron-spin resonance spectroscopy revealed that the small amount of cerium ions loaded into the Cu-SSZ-13 occupied the ion-exchange sites. The appropriate amount of cerium cations at the ion-exchange sites better stabilized the framework of SSZ-13 and thus led to the enhancement effect. By contrast, excessive ion-exchange with cerium adversely affected the hydrothermal stability of the Cu-SSZ-13, resulting in degraded SCR performance.

We demonstrate the preparation of highly ordered and graphitic mesoporous carbon nitride with an ordered porous structure and a high nitrogen content (MCN-ATN) by a nano-hard-templating approach through a simple polymerization of 3-amino-1,2,4-triazine (ATN) inside the pore channels of a mesoporous silica template with an Ia3d symmetry and a 3D porous structure. Powder X-ray diffraction and high resolution transmission electron microscopy analysis show that the prepared materials exhibit well-ordered mesopores with a 3D porous network. Nitrogen adsorption measurements also confirm that the samples possess excellent physical parameters including high surface areas (472-635 m 2 g À1 ), large pore volumes (0.71-0.99 cm 3 g À1 ) and tunable pore diameters (5.5-6.0 nm). One of the most important features of this work is that the cyclic aromatic precursor helps to preserve the nitrogen in the carbon matrix of the final product even after the carbonization process. The C/N ratio of the samples is ca. 0.92 which is much lower than that obtained for the samples prepared using ethylene diamine and carbon tetrachloride through a nano-hard templating process. X-ray photoelectron spectroscopy results reveal that MCN-ATN is mainly composed of sp 2 hybridized carbon atoms bonded with nitrogen atoms, associated with the triazine moieties from the ATN molecules. Temperature programmed desorption of CO 2 over MCN-ATN demonstrates that the sample is basic which originates from the amine groups on the surface of the CN wall structure. Finally, the samples are mounted on the quartz crystal microbalance (QCM) and used for sensing both acidic and basic organic vapors. Among the samples studied, MCN-ATN with the largest pore diameter showed a highly selective sensing performance for acidic molecules, especially the formic acid thanks to the presence of weak basic sites on the CN walls.

Improving the stability of porous materials for practical applications is highly challenging. Aluminosilicate zeolites are utilized for adsorptive and catalytic applications, wherein they are sometimes exposed to high-temperature steaming conditions (∼1000 °C). As the degradation of high-silica zeolites originates from the defect sites in their frameworks, feasible defect-healing methods are highly demanded. Herein, we propose a method for healing defects to create extremely stable high-silica zeolites. High-silica (SiO2/Al2O3 > 240) zeolites with *BEA-, MFI-, and MOR-type topologies could be stabilized by significantly reducing the number of defect sites via a liquid-mediated treatment without using additional silylating agents. Upon exposure to extremely high temperature (900–1150 °C) steam, the stabilized zeolites retain their crystallinity and micropore volume, whereas the parent commercial zeolites degrade completely. The proposed self-defect-healing method provides new insights into the migration of species through porous bodies and significantly advances the practical applicability of zeolites in severe environments.