基于新型NiFe氫化酶催化中心模擬物的光誘導(dǎo)產(chǎn)氫研究

李旭兵， 王旭喆， 宋子琪， 張麗萍， 佟振合， 吳驪珠

(中國科學(xué)院 理化技術(shù)研究所， 北京 100190)

論 文

基于新型NiFe氫化酶催化中心模擬物的光誘導(dǎo)產(chǎn)氫研究

(中國科學(xué)院 理化技術(shù)研究所， 北京 100190)

本文成功利用金屬中心為NiRu的NiFe氫化酶模擬物，在乙腈和水的混合溶劑中實現(xiàn)了人工光合成制氫。最優(yōu)條件下，體系基于NiRu催化劑的產(chǎn)氫TON值高達1893，前10 min的TOF為2.6 s-1，并且通過電化學(xué)測試對催化循環(huán)過程中所生成的金屬氫化物中間體進行了表征。

氫化酶模擬物； 光致產(chǎn)氫； 金屬氫化物

1 實驗部分

1.1 儀器與試劑

1HNMR：Bruker-400 核磁共振儀；質(zhì)譜：Shimadzu GC/MS-QP5050A質(zhì)譜儀；光源：藍光LEDs (450 nm)；電化學(xué)工作站：Princeton Appied Research Model 283 Potentiostat/Galvanostat；氣相色譜法：Techcomp 7890 Ⅱ。

1.2 實驗方法

NiRu化合物的合成[22]

取0.453 g (0.74 mmol) [(cymene)RuCl2]2和0.834 g (1.48 mmol) Ni(pdt)(dppe) 于舒?zhèn)惪似恐校诙栊詺夥毡Ｗo下將干燥的DCM加入到體系中，室溫攪拌4.0 h。隨著反應(yīng)的進行，溶液顏色逐漸加深。反應(yīng)結(jié)束后利用旋轉(zhuǎn)蒸發(fā)儀蒸干溶劑，柱層析進行快速分離 (乙腈∶甲醇=9∶1)，得到深紅色固體，產(chǎn)率約為50%。

1HNMR (CDCl3)∶ 7.80 (m, 4H), 7.50 (m, 16H), 7.16 (t,J=7.5 Hz, 4H), 5.43 (d,J=5.8 Hz, 2H), 5.48 (d,J= 5.8 Hz, 2H), 2.79 (m 1H), 2.31 (m, 8H), 2.21 (d,J=24.3 Hz, 4H), 1.98 (m, 2H), 1.20 (d,J=7.0 Hz, 6H). ESI-MS∶m/z835 [(cymene)Ru(Cl)(pdt)Ni(pdt)]+。

1.3 產(chǎn)氫實驗方法

取一支體積為20 mL的反應(yīng)管，將適量的Ru(bpy)3Cl2和H2A加入到體系中。隨后將體積比為1∶1的CH3CN和H2O的混合溶劑加入反應(yīng)體系中，調(diào)節(jié)溶液pH值，通Ar 30 min。然后用注射器快速打入適量NiRu催化劑，向體系中打入1.0 mL甲烷作為內(nèi)標。LEDs (450 nm， 3.0 W) 作為光源進行光照，光照一定時間時利用氣相色譜檢測體系中的氣體組成。

2 結(jié)果與討論

2.1 異核NiRu氫化酶模擬物合成

異核NiRu配合物參照文獻報道的方法合成[21,22]。利用Ni(dppe)(pdt) 和Ru(cymene)Cl2為原料，室溫條件下在二氯甲烷中攪拌即可得到目標產(chǎn)物 (產(chǎn)率～50%)，并通過核磁和高分辨質(zhì)譜等手段對NiRu配合物進行了表征 (圖1b)。

2.2 電化學(xué)測試

首先，電化學(xué)性質(zhì)測試表明NiRu配合物在乙腈中的還原電位為-1.10 VvsSCE。向體系中分別加入1.0 mmol/L、2.0 mmol/L和3.0 mmol/L的三氟乙酸，在-1.25vsSCE出現(xiàn)了新的還原峰 (圖2a)。根據(jù)文獻報道[21,22]，我們將該還原峰歸屬為NiRu配合物對應(yīng)的氫化物。如圖2b中所示，催化中心在得一個電子后失去Cl-，在H+存在條件下形成氫化物。氫化物是氫化酶模擬物在催化循環(huán)過程中一個比較重要的中間態(tài)，其可以繼續(xù)得到一個電子和質(zhì)子生成分子H2，從而完成整個催化循環(huán)過程。

圖1 (a) NiFe氫化酶結(jié)構(gòu)；(b) NiRu配合物相關(guān)合成步驟

圖2 (a) 循環(huán)伏安法測試：不同濃度的三氟乙酸條件下濃度為1.0 mmol/L NiRu氫化酶模擬物在乙腈中的電流變化情況 (掃描速度為100 mV/s，0.1 mol/L四正丁基六氟磷酸銨作為支持電解質(zhì))；(b) 電化學(xué)生成氫化物的機理(a)

2.3 光致產(chǎn)氫體系的條件優(yōu)化

3 結(jié)論

本文合成了一類新型的模擬NiFe氫化酶的以NiRu為金屬核心的氫化酶模擬物，我們首次成功地將其作為質(zhì)子還原的催化劑建立了光催化產(chǎn)氫體系。最優(yōu)條件下，體系可見光照20 min，基于催化劑的TON值可達1893，TOF 1.6 s-1(前10 min TOF為2.6 s-1)。這在基于NiFe氫化酶模擬物的產(chǎn)氫體系中為最高值 (文獻報道52 h-1)[14]，且效率能與基于FeFe氫化酶模擬物的產(chǎn)氫體系相媲美，在后續(xù)的實驗中我們將進一步深入研究其產(chǎn)氫機制并提高體系的穩(wěn)定性。

圖3 不同條件下體系產(chǎn)氫量隨時間變化其中1～4的條件為：NiRu催化劑濃度為10 μmol/L，光敏劑濃度為0.1 mmol/L，pH=5.0，H2A濃度為0.1 mol/L，CH3CN∶H2O分別為3∶1 (1)，1∶1(2)，1∶3 (3) 和1∶9 (4) 條件下H2量隨光照的變化。編號5～8為NiRu催化劑在體系中濃度為1.0 mmol/L，pH = 5.0，H2A濃度為0.1 mol/L，CH3CN∶H2O = 1∶1 (體積比)，隨光敏劑濃度變化1.0 mmol/L (5)，0.5 mmol/L (6)，0.3 mmol/L (7) 和0.1 mmol/L (8) 條件下H2隨光照時間的變化。9～12分別為NiRu催化劑在體系中濃度為10 μmol/L，光敏劑為0.1 mmol/L，pH=5.0，組成體系為CH3CN∶H2O = 1∶1 (體積比)，在含有不同濃度H2A為0.2 mol/L (9)，0.1 mol/L (10)，0.05 mol/L (11)和0.01 mol/L (12)條件下H2隨光照時間的變化。最后一組13～16為催化劑在體系中濃度為10 μmol/L，光敏劑為0.1 mmol/L，H2A濃度為0.1 mol/L，組成體系為CH3CN∶H2O = 1∶1 (體積比)，其中體系的pH值分別為6.0 (13)，5.0 (14)，4.0 (15)和3.0 (16) Photoinduced hydrogen production under different

圖4 光敏劑為0.5 mmol/L，pH = 4.0，H2A濃度為0.1 mol/L, CH3CN∶H2O = 1∶1 (體積比) 的條件下不同催化劑濃度對光催化產(chǎn)氫TON值的影響 CH3CN∶H2O =1∶1 solution under pH = 4.0 with different concentration of NiRu

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Photoinduced Hydrogen Evolution from a Novel [NiFe]-Hydrogenase Mimic

(TechnicalInstituteofPhysicsandChemistry,ChineseAcademyofSciences,Beijing100190,P.R.China)

We had successfully fabricated a photoinduced hydrogen evolution system from a novel [NiFe]-Hydrogenase Mimic with a NiRu center in the mixture of acetonitrile and water. Under the optimal conditions, the TON value for hydrogen evolution based on the catalyst was as high as 1893, and the TOF value was 2.6 s-1in the first ten minutes. Furthermore, the hydride intermidiate had been successfully observed by using electrochemical technique.

[NiFe]-Hydrogenase Mimics; photoinduced hydrogen evolution; metal hydride

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國家自然科學(xué)基金項目(2014CB239402, 2013CB834505和2013CB834804)項目資助

10.7517/j.issn.1674-0475.2015.05.411

1674-0475(2015)05-0411-06

2015-04-24收稿, 2015-05-30錄用