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Porous carbon nitride (CN) spheres with partially crystalline frameworks have been successfully synthesized via a nanocasting approach by using spherical mesoporous cellular silica foams (MCFs) as a hard template, and ethylenediamine and carbon tetrachloride as precursors. The resulting spherical CN materials have uniform diameters of ca. 4 μm, hierarchical three-dimensional (3-D) mesostructures with small and large mesopores with pore diameters centered at ca. 4.0 and 43 nm, respectively, a relatively high BET surface area of ~550 m 2 /g, and a pore volume of 0.90 cm 3 /g. High-resolution transmission electron microscope (HRTEM) images, wide-angle X-ray diffraction (XRD) patterns, and Raman spectra demonstrate that the porous CN material has a partly graphitized structure. In addition, elemental analyses, X-ray photoelectron spectra (XPS), Fourier transform infrared spectra (FT-IR), and CO 2 temperature-programmed desorption (CO 2 -TPD) show that the material has a high nitrogen content (17.8 wt%) with nitrogen-containing groups and abundant basic sites. The hierarchical porous CN spheres have excellent CO 2 capture properties with a capacity of 2.90 mmol/g at 25 °C and 0.97 mmol/g at 75 °C , superior to those of the pure carbon materials with analogous mesostructures. This can be mainly attributed to the abundant nitrogen-containing basic groups, hierarchical mesostructure, relatively high BET surface area and stable framework. Furthermore, the presence of a large number of micropores and small mesopores also enhance the CO 2 capture performance, owing to the capillary condensation effect.

A new series of Fe(II) and Co(II) complexes of sterically modulated 2,3,7,8-tetrahydroacridine-4,5(1H,6H)-diimine by substituted aryl rings are synthesized. The complex synthesis is achieved through a one-pot methodology by reacting one equivalent of 2,3,7,8-tetrahydroacridine-4,5(1H,6H)-dione with two equivalents of required aniline derivatives together with Fe or Co salt in boiling acetic acid. The single-crystal X-ray analyses of Fe and Co complexes bearing a 2,6-diisopropyl-substituted ligand, (N,N′E,N,N′E)-N,N′-(2,3,7,8-tetrahydroacridine-4,5(1H,6H)-diylidene)bis(2,6-diisopropylaniline), show a distorted trigonal-bipyramidal geometry for the metal center, a deviation from square-pyramidal geometry due to the opening up of the coordination sphere originating from structural rigidity of the carbonyl carbon atom achieved through cyclization. All the complexes show high activity toward ethylene activation when treated with methylaluminoxane as a cocatalyst. The ortho substituents of the aryl rings and the type of metal have a significant effect on ethylene activation and specifically on product distribution. The Fe complex with a 2,6-diisopropyl-substituted bis(imino)tetrahydroacridyl ligand produced polyethylene of moderate molecular weight (18 000). On changing the ortho substitution of the ligand from 2,6-diisopropyl to 2,6-dimethyl, the Co complexes produce polyethylene waxes and oligomers of predominantly α-olefins simultaneously, obeying Schulz−Flory distribution. The Co complexes bearing ligands with less sterically hindered substituents at the ortho position behave exclusively as dimerization catalysts.

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