Functionalization of metal–organic framework (MOF) ligands can tune the adsorption properties of MOFs. The adsorptions of NO, NO₂, NH₃, C₅H₅N, C₄H₅N, and C₄H₄O on pristine and five X-functionalized HKUST-1, i.e. Cu₃(BTC)₂ (BTC = 1,3,5-benzenetricarboxylate) (X = CH₃, CH₃O, NH₂, NO₂, and Br) are evaluated by van der Waals corrected density functional theory calculations. Despite the fact that the open metal center is the energetically preferred adsorption site for most of them, the functional group site can yield a comparable adsorption ability with the open metal center. This is particularly true for pyrrole C₄H₅N adsorption on CH₃O-functionalized HKUST-1 where the functional group site shows stronger adsorption stability than the open metal center site, probably due to the formed hydrogen bond between pyrrole and the CH₃O functional group. While the CH₃- or CH₃O-functionalized organic linker in these MOFs strengthens the adsorption of all the considered species, that of NO₂-, Br-, or NH₂-functional groups reduces, which is associated with their topologies. Among them, only CH₃- or CH₃O-functionalized HKUST-1 presents the fmj (orthorhombic crystal system) topology while all the others are isostructural to the pristine HKUST-1 with the tbo (twisted boracite-type, cubic) topological structure. Among six adsorbates, two basic adsorbates, C₅H₅N and NH₃, always yield the strongest bonding strength upon adsorption on the pristine and five functionalized HKUST-1. Electronic properties including the Bader charges, electron density differences, and electron localization function were investigated to comprehend their adsorption behaviors. This work provides guidance for the proper functionalization of HKUST-1 with improved adsorption properties for specific adsorbates.

中文翻译：

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接头功能化对HKUST-1中含氮化合物吸附的影响。

金属-有机骨架（MOF）配体的功能化可以调节MOF的吸附特性。NO，NO ₂，NH ₃，C ₅ H ₅ N，C ₄ H ₅ N和C ₄ H ₄ O在原始和五个X官能化的HKUST-1，即Cu ₃（BTC）₂（BTC = 1,3,5-三羧酸苯酯（X = CH ₃，CH ₃ O，NH ₂，NO ₂和Br）是通过范德华校正密度泛函理论计算得出的。尽管对于大多数金属而言，开放金属中心是能量上优选的吸附位点，但官能团位点可以产生与开放金属中心相当的吸附能力。对于吡咯C ₄ H ₅ N在CH ₃ O官能化的HKUST-1上的吸附尤其如此，其中官能团位点比开放的金属中心位点显示出更强的吸附稳定性，这可能是由于吡咯和CH ₃之间形成了氢键O功能组。而CH _3-或CH ₃这些MOF中的O-官能化有机连接基会增强所有考虑的物质的吸附，而NO _2-，Br-或NH _2-官能团的吸附会减少，这与它们的拓扑结构有关。其中，只有CH _3-或CH ₃ O-官能化的HKUST-1呈现fmj（斜方晶系）拓扑，而所有其他结构均与原始的HKUST-1具有tbo（扭曲的硼铁矿型，立方）拓扑结构同构。 。在六种吸附物中，两种碱性吸附物为C ₅ H ₅ N和NH ₃，当吸附在原始材料和五种功能化的HKUST-1上时，始终产生最强的粘合强度。研究了包括巴德电荷，电子密度差和电子定位功能在内的电子性质，以了解它们的吸附行为。这项工作为HKUST-1的适当功能化以及对特定吸附物的改进吸附性能提供了指导。