Preparation of quasi-homogeneous photocatalysts and the application in cross-dehydrogenation coupling reactions
Temperature-sensitive polymer materials P(MMA-co-VBCx%)were successfully prepared by emulsion polymerization using methyl methacrylate(MMA)and 1-(chloromethyl)-4-vinylbenzene(VBC)as monomers and 2,2'-azobis(2-methylpropionamidine)dihydrochloride(AIBA)as initiator.Rose Ben-gal(RB)was introduced into P(MMA-co-VBCx%)by grafting reaction to obtain UCST(upper critical solubility temperature)type quasi-homogeneous polymerization catalyst P(MMA-co-VBCx%)-RBy%.The structures of P(MMA-co-VBCx%)and P(MMA-co-VBCx%)-RBy%were characterized using 1 H NMR,FTIR and GPC;the UCST behaviors of the temperature-sensitive materials and Quasi-homogeneous cata-lysts were analyzed;and the cross-dehydrogenation coupling reaction(CDC)of N-aryl-tetrahydroisoquino-line(THIQ)and nitromethane(NM)was used as a model.The catalytic performance and reuse perform-ance of quasi-homogeneous catalysts were investigated.The results showed that the Tcp(cloud point)of P(MMA-co-VBCx%)decreased with increasing VBC content,and the Tcp of Quasi-homogeneous catalysts P(MMA-co-VBCx%)-RBy%decreased with increasing RB content.And the response temperatures of both types of polymers were located at40～60℃at the ethanol-water with a volume ratio of 4∶1;P(MMA-co-VBCx%)-RBy%has good dissolution-dissolution performance,and the recovery is greater than 90%at 5 dissolution-dissolution cycles;the catalytic activity of P(MMA-co-VBCx%)-RBy%is comparable to that of the homogeneous catalyst RB in catalyzing the reactions of THIQ and NM,and is applicable to the reac-tions of other derivatives.The catalyst can be recovered by lowering the temperature and reused 5 times with no significant decrease in catalytic activity.
UCST type polymervisible light photocatalysisRose Bengal(RB)cross-dehydrogenation coupling reaction
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