Ureidopropyl group

A further example of a cooperative catalytic system is a bifunctionalized mesoporous silica nanosphere material (MSN) containing the ureidopropyl group (UDP) and 3-[2-(2-aminoethylamino)ethylamino]propyl group (AEP). All catalysts were synthesized by a sol-gel procedure similar to the previously mentioned one by using different AEP/UDP molar ratios. The MSN-AEP/ UDP catalyst was employed for the aldol, Henry and cyanosilylation reactions (Scheme 3.8 R = NO2, R" = H, Schemes 3.35 and 3.36, respectively) and TON values were compared with those observed by using MSN-AEP and MSN-UDP catalysts (Table 3.10). 

Quantitative estimation of ureidopropyl groups was performed by CHNS analysis. Nitrogen content for all organosihcas was determined using a LECO model CHNS-932 elemental analyzer from St. Joseph, MI. 

Figure 3. (A) The weight change (TG) curves measured in flowing nitrogen for the SBA-15 samples with ureidopropyl groups calcined pure silica (UP-0) and extracted organosilicas (UP-5, UP-10, UP-15, UP-20) and as-synthesized sample (UP-15t) with various percentages of ureidopropyl ligands, and (B) the corresponding DTG curves.

In conclusion, this work shows that the co-condensation synthesis afforded SBA-15 materials with relatively large amount of ureidopropyl groups (up to 15%) on the mesopore walls withont significant deterioration of the structural ordering. The resulting materials exhibit high surface areas, large pore volume and pore widths about 9 nm. 

ADSORPTION STUDIES OF SBA-15 MESOPOROUS SILICA WITH UREIDOPROPYL SURFACE GROUPS... 

In this study, we report the co-condensation synthesis of hexagonally ordered organosiUca, SB A-15, with ureidopropyl (UP) surface groups on the pore walls (see scheme 1). 

Table 1. Molar composition and N% for the synthesis gels used and the corresponding N% for the SBA-15 silicas with ureidopropyl surface groups. ...

Figure 2. (A) Nitrogen adsorption-desorption isotherms measured at -196 °C for the extracted mesoporous channel-like SBA-15 silicas with ureidopropyl surface groups. The isotherms for UP-0, UP-5, UP-10 and UP-15 were offset vertically by 800, 550, 275 and 80 cc STP g, respectively. (B) Pore size distributions (PSDs) calculated according to the KJS method [24] for each nitrogen adsorption isotherm. The pore size distributions UP-0, UP-5, UP-10 and UP-15 were shifted vertically by 2,1.05, 0.55 and 0.2 cc g nm, respectively.

---