1,2-亚苯基二硫桥[FeFe]-氢化酶模拟物选择性光催化还原CO2至CO

利用基于非贵金属的分子催化剂通过光驱动催化CO2还原生成CO是将太阳能储存为化学能和缓解CO2温室效应的有效途径之一,具有重要的科学意义和潜在的应用前景.已报道的非贵金属分子催化剂,大多数对于光驱动CO2还原表现出缓慢的催化反应速率和/或对CO产物的低选择性,反应常常伴随着质子还原产氢反应,只有很少几种非贵金属分子催化剂对光催化CO2还原生成CO表现出高催化反应速率(>100 h?1)和高选择性.研究表明,双核过渡金属配合物由于分子中邻近的两个金属中心的协同催化作用,对于CO2还原生成CO的催化活性明显高于相应的单核配合物.因此,具有两个邻近的金属离子的非贵金属双核配合物有望作为CO2选择性还原的高效分子催化剂.我们最近的研究发现,具有刚性、共轭亚苯基二硫桥结构的FeFe]-氢化酶模拟物(μ-bdt)Fe2(CO)6](1,bdt=苯-1,2-二巯基)能够高活性、高选择性地光化学还原CO2至CO,而与其类似的模拟物(μ-edt)Fe2(CO)6](2,edt=乙烷-1,2-巯基)则不具有光催化还原CO2活性,表明铁铁氢化酶模拟物中硫-硫桥的结构是影响模拟物的催化性能的重要结构因素之一.可见光照射1/Ru(bpy)3]2+/BIH(BIH=1,3-二甲基-2-苯基-2,3-二氢-1H-苯并d]-咪唑)体系4.5 h,1催化生成CO的循环数(TON)为710,在初始1 h的转化率(TOF)为7.12 min^-1,CO的选择性达到97%,内量子效率为2.8%.有趣的是,向体系中加入TEOA时可以调节1的催化选择性,光化学反应能够在CO2还原产生CO和质子还原产生H2之间进行切换.此外,采用稳态荧光和瞬态吸收光谱研究了光催化体系中的电子转移,提出可能的光催化反应机理.该研究结果揭示了刚性硫-硫桥结构的氢化酶模拟物对光化学CO2还原至CO的特殊催化活性,拓展了铁铁氢化酶模拟物的催化多功能性.

Selective photocatalytic reduction of CO2 to CO mediated by a [FeFe]-hydrogenase model with a 1,2-phenylene S-to-S bridge

Photocatalytic reduction of CO2 to CO is a promising approach for storing solar energy in chemicals and mitigating the greenhouse effect of CO2.Our recent studies revealed that(μ-bdt)Fe2(CO)6](1,bdt=benzene-1,2-dithiolato),aFeFe]-hydrogenase model with a rigid and conjugate S-to-S bridge,was catalytically active for the selective photochemical reduction of CO2 to CO,while its analogous complex(μ-edt)Fe2(CO)6](2,edt=ethane-1,2-dithiolato)was inactive.In this study,it was found that the turnover number of 1 for CO evolution reached 710 for the 1/Ru(bpy)3]2+/BIH(BIH=1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzod]-imidazole)system under optimal conditions over 4.5 h of visible-light irradiation,with a turnover frequency of 7.12 min?1 in the first hour,a high selectivity of 97%for CO,and an internal quantum yield of 2.8%.Interestingly,the catalytic selectivity of 1 can be adjusted and even completely switched in a facile manner between the photochemical reductions of CO2 to CO and of protons to H2 simply by adding different amounts of triethanolamine to the catalytic system.The electron transfer in the photocatalytic system was studied by steady-state fluorescence and transient absorption spectroscopy,and a plausible mechanism for the photocatalytic reaction was proposed.