Dynamic Spectrochemical studies on Metal Clusters in Confined Microspace

我们研制了一套时间分辨FTIR（Bio-Rad，FTS 60 A/896）光谱系统，该系统与MOPO和Yag激光触发器联用，时间分辨率为5 μ s-ms。我们利用该系统研究了<18><2-><12><24><2->在300- 327 K的CO+H_2O和NO+CO反应气氛下，NaY沸石（13 * 直径）微孔中金属羰基簇合物[Pt_9（CO）_ ]^和[Pt_（CO）_ ]^在激光脉冲激发下的动力学行为，并对CO在Rh/SiO_2和CO+H_2在Ni/SiO_2上的光脱附反应中形成的表面物种进行了原位观察。我们利用<15>“瓶中船”技术在NaY微孔和FSM-16有序介孔中合成了Pt_9-Pt_6和Ru_6羰基簇合物和Pt_9-RhIr、RuCo和RuFe簇合物，并用EXAFS/TEM、FTIR和UV-VIS对其进行了表征，并研究了簇合物骨架的可逆转变 ...更多信息 在微孔中。研究项目的其他主题简述如下。(1)NaY<12>分子筛合成的Pt_2和Pt_9羰基簇阴离子在汞灯照射下促进CO+H_2O反应生成CO_2fH_2。时间分辨红外光谱研究表明，在<12>680 nm激光脉冲辐照下，NaY超笼中的Pt_羰基被有效激发和转化，导致团簇溶剂化水分子在70 ms内发生热活化。(2)用时间分辨FTIR研究了Rh/SiO_2和Ni/SiO_2催化剂在CO+H_2反应中[CHx]和[OH]物种的动力学行为。(3)快速扫描FTIR/EXAFS研究表明，[Pt_（CO）_ ]^ /NaY催化剂上CO还原NO生成N_2（N_2O）的反应<12><24>是<2->通过簇合物骨架（Pt_<12>（CO）_<24>]^<2->/NaY&lt;=&gt;[“Pt_3（CO）_6”+Pt（CO）]/NaY的可逆转化进行的。(4)用快速扫描FTIR/EXAFS研究了300- 373 K时NO在Au（1）NaY上分解为N_2（N_2O）+O_2的机理，以及NO与H_2的选择性还原为N_2+H_2O而不生成NH_3和由于在催化剂表面上特异性生成“NO_2（N_2O_4）”而有效的氧促进反应的机理。少

We have insutaled a time-resolved FTIR (Bio-Rad, FTS60A/896) spectroscopic system coupled with MOPO and Yag Laser-triger with a 5 mus-ms time-resolution. We have applied this system to study the dynamic behavior of metal carbonyl clusters such as [Pt_9(CO)_<18>]^<2-> and [Pt_<12>(CO)_<24>]^<2-> encapsulated in the confined micropores of NaY zeolite (13 * diamter) after a laser-pulse excitation under the CO+H_2O and NO+CO reaction atmospheres at 300-327K.Additionally, we have studied a in-situ observation of surface species formed in a photo-desorption of CO on Rh/SiO_2 and CO+H_2 reaction on Ni/SiO_2 by the ms resolution. We extended works to synthesize Pt_9-Pt_<15> and Ru_6 carbonyl cluster complexes and bimetallic RhIr, RuCo and RuFe bimetal clusters inside micropores of NaY and ordered mesopores of FSM-16 by the "ship-in-bottle" technique, which have been characterized by EXAFS/TEM,FTIR,and UV-VIS,which have been investigated on their reversible transformation of cluster frameworks … More in micropores. Other topics of research project are briefly summarized as follows.(1) Pt_<12> and Pt_9 carbonyl cluster anions synthesized NaY zeolite promote a CO+H_2O reaction to produce CO_2fH_2 substantially unders the iluimation of Hg lamp. The time-resolved IR study suggested that the Pt_<12> carbonyl in NaY supercage are effectively excited and transformed, resulting in the thermal activation of the cluster-solvated water molecules in 70 ms uncder the pulse-irradiation of the 680 nm laser light.(2) The time-resolved FTIR studies have been conducted to reveal the dynamic behaviors of [CHx] and [OH] species formed Rh/SiO_2 and Ni/SiO_2 in CO+H_2 reaction.(3) The rapid-scan FTIR/EXAFS studies showed the NO reduction with CO to form N_2 (N_2O) proceeded catalytically on [Pt_<12>(CO)_<24>]^<2->/NaY via the reversible tranformation of their cluster frameworks (Pt_<12>(CO)_<24>]^<2->/NaY<==>["Pt_3(CO)_6"+Pt(CO)]/NaY.(4) By the rapid-scan FTIR/EXAFS studies it was di scussed on the mechanism of NO decomposition towards N_2(N_2O)+O_2 on Au(1)NaY at 300-373K,and selective reduction of NO with H_2 to give N_2+H_2O without formation of NH_3 and an effective oxygen promotion of the reaction due to the specific formation of "No_2(N_2O_4)" on the catalyst surface. Less