Thinking Outside the Cage: Controlling the Extrinsic Porosity and Gas Uptake Properties of Shape-Persistent Molecular Cages in Nanoporous Polymers
Thinking Outside the Cage: Controlling the Extrinsic Porosity and Gas Uptake Properties of Shape-Persistent Molecular Cages in Nanoporous Polymers
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DOI：
10.1021/acs.chemmater.5b01346
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发表时间：
2015-06-09
影响因子：
8.6
通讯作者：
Coskun, Ali
中科院分区：
文献类型：
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作者：
Buyukcakir, Onur;Seo, Yongbeom;Coskun, Ali
我们提出了一种新的策略，引入本地秩序到无定形纳米多孔聚合物使用形状持久的有机笼化合物作为分子构建块的多孔笼框架（pCAGEs）的合成没有任何金属催化剂在环境友好的条件下。我们已经证明，通过改变有机连接体的大小和尺寸，可以控制纳米多孔聚合物内的有机笼的非本征孔隙率，从而使我们能够调节无定形pCAGE的表面积和气体吸收特性。pCAGE（SA（BET）= 628.7-844.3 m（2）g（-1））显示出显著高的CO2吸收能力（在1 bar，273 K下高达4.21 mmol g（-1）），具有突出的CO2/N-2 IAST选择性（高达100）。与先前报道的三嗪基聚合物不同，pCAGE在高负载下对CO2显示出高达42.9 kJ mol（-1）的异常等排吸附热（Q（st））值。我们将CAGE对CO2的高亲和力归因于CAGE单体的超微孔性（固有孔隙率）所产生的“笼效应”的存在。为了证明笼效应，我们合成了一个控制聚合物纳入半CAGE作为单体单元。与CAGE和pCAGE相比，所得聚合物显示出显著更低的Q（st）值，表明存在笼效应。此外，在对照聚合物的情况下，对表面积的控制完全丧失，从而显示了CAGE单体作为结构单元的重要性和所产生的局部有序性。
We present a new strategy to introduce local-order into amorphous nanoporous polymers using shape-persistent organic cage compounds as molecular building blocks in the synthesis of porous cage frameworks (pCAGEs) without any metal catalyst under environmentally benign conditions. We have demonstrated that by varying the size and dimension of the organic linkers extrinsic porosity of organic cages within nanoporous polymers can be controlled, thus allowing us to tune the surface area and gas uptake properties of amorphous pCAGEs. pCAGEs (SA(BET) = 628.7-844.3 m(2) g(-1)) revealed significantly high CO, uptake capacities (up to 4.21 mmol g(-1) at 1 bar, 273 K) with prominent CO2/N-2 IAST selectivities (up to 100). Unlike previously reported triazine-based polymers, pCAGEs showed exceptional isosteric heats of adsorption (Q(st)) values up to 42.9 kJ mol(-1) for CO2 at high loading. We attribute the high affinity of CAGE toward CO2 to the presence of a "cage effect" arising from ultramicroporosity (intrinsic porosity) of CAGE monomers. To prove the cage effect, we have synthesized a control polymer incorporating half-CAGEs as monomeric units. The resulting polymer showed substantially lower Q(st) values compared to the CAGE and pCAGEs indicating the presence of the cage effect. In addition, the control over the surface area in the case of control polymer was lost completely, thus showing the importance of CAGE monomers as building blocks and the resulting local-order.