Directing the Breathing Behavior of Pillared-Layered Metal Organic Frameworks via a Systematic Library of Functionalized Linkers Bearing Flexible Substituents
Directing the Breathing Behavior of Pillared-Layered Metal Organic Frameworks via a Systematic Library of Functionalized Linkers Bearing Flexible Substituents
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DOI：
10.1021/ja302991b
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发表时间：
2012-06-06
影响因子：
15
通讯作者：
Fischer, Roland A.
中科院分区：
文献类型：
--
作者：
Henke, Sebastian;Schneemann, Andreas;Fischer, Roland A.
柔性金属有机骨架（MOFs），也被称为软多孔晶体（SPC），显示可逆的结构转变依赖于吸附的客体分子的性质和数量。在最近的研究中，已经报道了有机连接基的共价官能化可以影响或甚至整合M0 F中的框架柔性（“呼吸”）。然而，这种响应特性的合理微调是非常可取的，但也具有挑战性。在这里，我们提出了一个强大的方法，有针对性地操纵的响应性和框架的灵活性的一个重要的家庭的柱撑层状的MOFs的基础上的母体结构[Zn-2（bdc）（2）（dabco）1（bdc = 1，4-benzenedicarboxylate; dabco = 1，4-diazabicyclo[2.2.2]octane）。功能化的bdc-型连接体（fu-bdc），其中携带额外的悬挂侧基在不同位置的苯核心（烷氧基不同的链长与不同的功能和极性），库被生成。材料[Zn-2（fu-bdc）（2）（dabco）]（n）的合成产生高响应性MOF的相应集合。母体MOF仅具有弱柔性;然而，[Zn-2（fu-bdc）（2）（dabco）]（n）的取代骨架在除去客体时急剧收缩，并在吸附DMF（N，N-二甲基甲酰胺）、EtOH或CO2等时再次膨胀，而N-2几乎不被吸附并且不打开窄孔形式。这些“呼吸”动力学归因于作为固定化“客体”的悬挂侧链，其与移动的客体分子以及与它们自身和与框架骨架相互作用。无客体、收缩形式和气体吸附行为（相变压力、滞后回线）的结构细节高度依赖于连接体处的取代基的性质，因此可以使用我们的方法进行调整。将我们的官能化连接体库与混合组分MOF（固溶体）的概念相结合，提供了非常丰富的定制结构动力学和响应性的额外维度。以不同比率实施两种不同官能化的连接剂产生具有增加的固有复杂性的多组分单相[Zn-2（fu-bdc”）（2x）（fu-bdc”）（2-2x）（dabco）]（n）M0 F（0 < x < 1），其特征在于其气体吸附性质对所施加的组分比率的非线性依赖性。因此，这种柱撑层状MOFs的响应行为可以通过官能化连接体的智能组合来广泛调节。
Flexible metal organic frameworks (MOFs), also referred to as soft porous crystals (SPCs), show reversible structural transitions dependent on the nature and quantity of adsorbed guest molecules. In recent studies it has been reported that covalent fiinctionalization of the organic linker can influence or even integrate framework flexibility ("breathing") in MOFs. However, rational fine-tuning of such responsive properties is very desirable but challenging as well. Here we present a powerful approach for the targeted manipulation of responsiveness and framework flexibility of an important family of pillared-layered MOFs based on the parent structure [Zn-2(bdc)(2)(dabco)1 (bdc = 1,4-benzenedicarboxylate; dabco = 1,4-diazabicyclo[2.2.2]octane). A library of functionalized bdc-type linkers (fu-bdc), which bear additional dangling side groups at different positions of the benzene core (alkoxy groups of varying chain length with diverse functionalities and polarity), was generated. Synthesis of the materials [Zn-2(fu-bdc)(2)(dabco)](n) yields the respective collection of highly responsive MOFs. The parent MOF is only weakly flexible; however, the substituted frameworks of [Zn-2(fu-bdc)(2)(dabco)](n) contract drastically upon guest removal and expand again upon adsorption of DMF (N,N-dimethylformamide), EtOH, or CO2, etc., while N-2 is hardly adsorbed and does not open the narrow-pored form. These "breathing" dynamics are attributed to the dangling side chains that act as immobilized "guests", which interact with mobile guest molecules as well as with themselves and with the framework backbone. The structural details of the guest-free, contracted form and the gas sorption behavior (phase transition pressure, hysteresis loop) are highly dependent on the nature of the substituent at the linker and can therefore be adjusted using our approach. Combining our library of functionalized linkers with the concept of mixed-component MOFs (solid solutions) offers very rich additional dimensions of tailoring the structural dynamics and responsiveness. Implementation of two differently functionalized linkers in varying ratios yields multicomponent single-phased [Zn-2(fu-bdc')(2x)(fu-bdc")(2-2x)(dabco)](n) MOFs (O < x < 1) of increased inherent complexity, which feature a non-linear dependence of their gas sorption properties on the applied ratio of components. Hence, the responsive behavior of such pillared-layered MOFs can be extensively tuned via an intelligent combination of functionalized linkers.