Hatem M. Alsyouri

A first-time, end group thermolysis departing a urethane into propylene carbonate. This exposure produced a new amine tethering point producing a diamine-terminated oligourea ([10]-OU) as a green sorbent for CO ₂ capturing is reported.

A new series of [n]‐oligoureas ([n]‐OUs, n=4, 7, 10, and 12) green solid sorbents was prepared following a base‐catalyzed, microwave‐assisted oligomerization reaction. The materials were characterized by NMR and IR spectroscopy, elemental analysis, thermogravimetric analysis, differential scanning calorimetry, and XRD. Decomposition temperatures at 50 % weight loss (T_d50) were ca. 350 °C for all oligomers. Urea and urethane functional groups indicated by IR spectroscopy confirmed the formation of the sorbent. The CO₂ capturing capacities were determined at 35 °C and 1.0 bar (gravimetric method). Accordingly, [10]‐OU had the highest CO₂ sorption capacity among the others (18.90 and 22.70 mg g_sorbent⁻¹) at two different activation temperatures (60 or 100 °C, respectively). Chemisorption was the principal mechanism for CO₂ capture. Cyclic CO₂ sorption/desorption measurements were carried out to test the recyclability of [10]‐OU. Activating the sample at 60 °C, three stable CO₂ sorption cycles were achieved after running the first cycle.

Acidic interfacial growth can provide a number of industrially important mesoporous silica morphologies including fibers, spheres, and other rich shapes. Studying the reaction chemistry under quiescent (no mixing) conditions is important for understanding and for the production of the desired shapes. The focus of this work is to understand the effect of a number of previously untested conditions: acid type (HCl, HNO3, and H2SO4), acid content, silica precursor type (TBOS and TEOS), and surfactant type (CTAB, Tween 20, and Tween 80) on the shape and structure of products formed under quiescent two-phase interfacial configuration. Results show that the quiescent growth is typically slow due to the absence of mixing. The whole process of product formation and pore structuring becomes limited by the slow interfacial diffusion of silica source. TBOS-CTAB-HCl was the typical combination to produce fibers with high order in the interfacial region. The use of other acids (HNO3 and H2SO4), a less hydrophobic silica source (TEOS), and/or a neutral surfactant (Tweens) facilitate diffusion and homogenous supply of silica source into the bulk phase and give spheres and gyroids with low mesoporous order. The results suggest two distinct regions for silica growth (interfacial region and bulk region) in which the rate of solvent evaporation and local concentration affect the speed and dimension of growth. A combined mechanism for the interfacial bulk growth of mesoporous silica under quiescent conditions is proposed.