鐵金屬紫質修飾之二氧化鈦的合成與其在氧化催化反應之研究

Abstract

利用紫質分子優異的吸光能力來加強二氧化的光催化性質，一直是化學家們努力的目標之一。近年來的研究發現，紫質分子在meta或para不同位向的錨定基團會影響其與二氧化鈦的鍵結模式、吸附數量、電子傳遞能力和氧化催化能力，因此在本篇論文中，我們合成出兩種能夠和二氧化鈦產生不同鍵結模式的鐵金屬紫質化合物，將之修飾在二氧化鈦表面上，並探討其光催化能力。

在光催化降解4-Nitrophenol方面，利用meta取代的紫質修飾二氧化鈦能夠在照光反應條件下，於5小時內降解90%以上的4-Nitrophenol，比較未修飾紫質的二氧化鈦在相同時間的照光條件下，只能降解35%左右，其他酚類也能夠有效地進行降解反應。而未照光條件下，則沒有觀察到有光降解反應發生。因此我們推論修飾紫質的確能夠增進二氧化鈦的光催化能力。

此催化系統也可以在氧氣當氧化劑並加入自由基引發劑NHPI的條件下將苯乙烷氧化成苯乙酮，如果更進一步加入鐵金屬吡啶、光電子捕捉劑或改變紫質軸向的配位基團，可提升氧化催化反應之產率。在最佳的催化狀態下，苯乙烷能在1 atm的氧氣、1 mol% NHPI與軸向配位基為吡啶的紫質修飾二氧化鈦共催化下，氧化成苯乙酮，並得到64%的產率。

Using porphyrin to reinforce photocatalytic capability of TiO2 has always been a target for chemists to work with. Recent research of TPP indicates that the anchoring groups at meta or para position can affect the binding geometries of the porphyrins onto TiO2, the amount of binding porphyrins, the electron transfer property and the catalytic activity of oxidation reactions. Thus, in this thesis, we synthesize three kinds of iron or zinc tetraphenylporphyrins with carboxyl substitunents at the meta or para position of the phenyl groups on the TPP and further immobilized onto the surface of titanium dioxide. In photodegradation of phenolic compound, the meta position porphyrin-TiO2 catalyst was able to carry out the degradation over 90% of 4-Nitrophenol under 5 hours illumination of visible light. Other phenols can also undergo degradation by using this catalyst. Compare to non-modified TiO2 catalyst, only 35% of 4-nitrophenol was degraded under the same conditions. Without illumination, no photo-degradation was observed, suggest that modification of porphyrin on TiO2 indeed promote the photocatalytic ability. This system can also be used to catalyze the oxidation of ethylbenzene into acetophenone with molecular oxygen in the presence of an initiator NHPI. The combination of iron-pyridine or viologen and porphyrins immobilized onto TiO2 or change the axial ligand to pyridine can further improve the yield of the oxidation. Under optimal conditions, oxidation of ethylbenzene into acetophenone under 1 atm O2 and 1 mol% NHPI reach to 64% yield.