Enhancement of CO2 Adsorption and Catalytic Properties by Fe-Doping of [Ga2(OH)2(L)] (H4L = Biphenyl-3,3',5,5'-tetracarboxylic Acid), MFM-300(Ga2).
Enhancement of CO2 Adsorption and Catalytic Properties by Fe-Doping of [Ga2(OH)2(L)] (H4L = Biphenyl-3,3',5,5'-tetracarboxylic Acid), MFM-300(Ga2).
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DOI：
10.1021/acs.inorgchem.5b02108
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发表时间：
2016-02-01
影响因子：
4.6
通讯作者：
Schröder M
中科院分区：
文献类型：
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作者：
Krap CP;Newby R;Dhakshinamoorthy A;García H;Cebula I;Easun TL;Savage M;Eyley JE;Gao S;Blake AJ;Lewis W;Beton PH;Warren MR;Allan DR;Frogley MD;Tang CC;Cinque G;Yang S;Schröder M
金属有机骨架（mof）通常是用一种金属离子合成的，而含有不同金属离子混合物的mof是一种增强和调节材料性能的方法。我们报道了用Ga(NO3)3和H4L在DMF、THF和含HCl的水的混合物中溶剂热反应3天合成[Ga2(OH)2(L)] （H4L =联苯-3,3 ',5,5 ' -四羧酸），命名为MFM-300(Ga2), （MFM = Manchester Framework Material代替NOTT名称）。MFM-300（Ga2）在四边形空间基团I4122中结晶，a = b = 15.0174(7) Å和c = 11.9111（11） Å，与Al（III）类似物MFM-300（Al2）具有相同的结构，气孔上装饰有连接Ga（III）中心的−OH基团。Fe(NO3)3和Ga(NO3)3的均相混合物与联苯-3,3 ',5,5 ' -四羧酸反应，在与MFM-300（Ga2）相似的条件下制备了同结构掺铁材料[Ga1.87Fe0.13(OH)2(L)] MFM-300（Ga1.87Fe0.13）。以Fe(NO3)3和相同的配体为原料，通过水热法制备了Fe（III）基材料[Fe3O1.5(OH)(HL)(L)0.5(H2O)3.5] MFM-310（Fe）。[MFM-310(Fe)]在正交空间群Pmn21 (a = 10.560(4) Å， b = 19.451(8) Å， c = 11.773(5) Å中结晶，并结合配体连接的μ3-氧中心三核铁簇节点，形成与MFM-300系列不同的三维无孔骨架。因此，Fe掺杂可以用来监测母体Ga（III）框架内杂原子中心的影响，而不需要合成同结构Fe（III）类似物[Fe2(OH)2(L)], MFM-300(Fe2)，这是我们迄今为止无法制备的。fe掺杂的MFM-300（Ga2）对气体吸附能力有积极的影响，特别是对CO2的吸附，其中MFM-300（Ga1.87Fe0.13）的CO2吸附能力比同金属母材提高了49%。因此，我们在此报告了基于ga的MOF的最高CO2吸收量（2.86 mmol g-1, 273 K, 1 bar）。测定了MFM-300(Ga2)-solv、MFM-300（Ga2）、MFM-300（Ga2）·2.35CO2、MFM-300(Ga1.87Fe0.13)-solv、MFM-300（Ga1.87Fe0.13）、MFM-300（Ga1.87Fe0.13）·2.0CO2的单晶x射线结构。最值得注意的是，气体负载材料的原位单晶衍射研究表明，fe掺杂对孔隙中CO2结合的分子细节有显著影响，在这些框架材料中，桥接的M-OH羟基是CO2的首选结合位点。在原位同步红外光谱测量CO2结合相对于孔中的- OH基团与上述结构分析是一致的。此外，我们发现，与MFM-300（Ga2）相比，fe掺杂的MFM-300（Ga1.87Fe0.13）对苯乙烯氧化物开环反应的催化性能有所提高，但对苯甲醛室温乙酰化反应的催化活性相似。讨论了铁掺杂在这些体系中的作用，作为增强孔隙率和母材结构完整性的机制。通过结合原位单晶x射线衍射和原位偏振红外光谱研究，获得了装载二氧化碳的MFM-300（Ga2）和混合gae类似物的关键结构见解。这些静态和动态实验表明，吸附在MFM-300（Ga2）中的CO2分子与孔表面的自由- OH基团形成氢键，并且发现了先前未观察到的分子间偶极子相互作用模式，以稳定孔内的两个CO2分子。
Metal–organic frameworks (MOFs) are usually synthesized using a single type of metal ion, and MOFs containing mixtures of different metal ions are of great interest and represent a methodology to enhance and tune materials properties. We report the synthesis of [Ga2(OH)2(L)] (H4L = biphenyl-3,3′,5,5′-tetracarboxylic acid), designated as MFM-300(Ga2), (MFM = Manchester Framework Material replacing NOTT designation), by solvothermal reaction of Ga(NO3)3 and H4L in a mixture of DMF, THF, and water containing HCl for 3 days. MFM-300(Ga2) crystallizes in the tetragonal space group I4122, a = b = 15.0174(7) Å and c = 11.9111(11) Å and is isostructural with the Al(III) analogue MFM-300(Al2) with pores decorated with −OH groups bridging Ga(III) centers. The isostructural Fe-doped material [Ga1.87Fe0.13(OH)2(L)], MFM-300(Ga1.87Fe0.13), can be prepared under similar conditions to MFM-300(Ga2) via reaction of a homogeneous mixture of Fe(NO3)3 and Ga(NO3)3 with biphenyl-3,3′,5,5′-tetracarboxylic acid. An Fe(III)-based material [Fe3O1.5(OH)(HL)(L)0.5(H2O)3.5], MFM-310(Fe), was synthesized with Fe(NO3)3 and the same ligand via hydrothermal methods. [MFM-310(Fe)] crystallizes in the orthorhombic space group Pmn21 with a = 10.560(4) Å, b = 19.451(8) Å, and c = 11.773(5) Å and incorporates μ3-oxo-centered trinuclear iron cluster nodes connected by ligands to give a 3D nonporous framework that has a different structure to the MFM-300 series. Thus, Fe-doping can be used to monitor the effects of the heteroatom center within a parent Ga(III) framework without the requirement of synthesizing the isostructural Fe(III) analogue [Fe2(OH)2(L)], MFM-300(Fe2), which we have thus far been unable to prepare. Fe-doping of MFM-300(Ga2) affords positive effects on gas adsorption capacities, particularly for CO2 adsorption, whereby MFM-300(Ga1.87Fe0.13) shows a 49% enhancement of CO2 adsorption capacity in comparison to the homometallic parent material. We thus report herein the highest CO2 uptake (2.86 mmol g–1 at 273 K at 1 bar) for a Ga-based MOF. The single-crystal X-ray structures of MFM-300(Ga2)-solv, MFM-300(Ga2), MFM-300(Ga2)·2.35CO2, MFM-300(Ga1.87Fe0.13)-solv, MFM-300(Ga1.87Fe0.13), and MFM-300(Ga1.87Fe0.13)·2.0CO2 have been determined. Most notably, in situ single-crystal diffraction studies of gas-loaded materials have revealed that Fe-doping has a significant impact on the molecular details for CO2 binding in the pore, with the bridging M–OH hydroxyl groups being preferred binding sites for CO2 within these framework materials. In situ synchrotron IR spectroscopic measurements on CO2 binding with respect to the −OH groups in the pore are consistent with the above structural analyses. In addition, we found that, compared to MFM-300(Ga2), Fe-doped MFM-300(Ga1.87Fe0.13) shows improved catalytic properties for the ring-opening reaction of styrene oxide, but similar activity for the room-temperature acetylation of benzaldehyde by methanol. The role of Fe-doping in these systems is discussed as a mechanism for enhancing porosity and the structural integrity of the parent material. Key structural insights were obtained for CO2-loaded MFM-300(Ga2) and mixed GaFe analogues by combining in situ single-crystal X-ray diffraction and in situ polarized IR spectroscopic studies. These static and dynamic experiments revealed that the adsorbed CO2 molecules in MFM-300(Ga2) form hydrogen bonds with the free −OH groups on the surface of the pores, and a previously unobserved pattern of intermolecular dipole interactions was found to stabilize two CO2 molecules within the pores.