High gas storage capacities and stepwise adsorption in a UiO type metal–organic framework incorporating Lewis basic bipyridyl sites

Abstract

A UiO type MOF with Lewis basic bipyridyl sites was synthesized and structurally characterized. After being activated by Soxhlet-extraction, this MOF exhibits high storage capacities for H 2 , CH 4 and CO 2 , and shows unusual stepwise adsorption for liquid CO 2 and solvents, indicating a sequential filling mechanism on different adsorption sites.Developing an effective system for carbon dioxide capture from anthropogenic emissions and finding appropriate mediums for energy gas (i.e., H 2 and CH 4 ) storage have been long term challenges, and will be increasingly urgent in future. 1 Physical sorption using solid state absorbents provides efficient alternatives owing to fast kinetics and high energy efficiency. 2 Indeed, some pilot plants for carbon dioxide capture and methane storage using solid state absorbents have been realized by some research groups. 3 Established as a new class of crystalline porous materials, metal-organic frameworks (MOFs) provide ideal platforms for such applications due to their intriguing structures, high surface area and tuneable functional pore environments. 4 In order to achieve high gas storage capacities or high selectivity, extensive efforts have been devoted to increase the affinity of frameworks with gas molecules, such as generating open metal sites 5 or tuning pore environments by immobilizing functional groups on the pore surface. 6 Immobilizing functional groups appears to be a promising strategy to tune the adsorption properties, especially for enhancing CO 2 binding strength by incorporating Lewis basic sites. However, the conventional strategy of anchoring the functional groups has some drawbacks. Along with the modification of the pore environments, the space occupation or blockage of functional groups always decreases the pore volume as well as specific surface areas significantly, which contrariwise lower the gas uptake capacities. 7 In this respect, the N-heterocyclic ligands are more attractive due to their benefits of constructing isomorphic MOFs and incorporating functional Lewis basic sites into the pore surface without declining their original pore spaces. 8 The UiO types of MOFs are an emerging class of MOFs that attract broad interest. 9 The highly porous structures and excellent stability of these types of MOFs allow them to be promising materials for the targets of CO 2 capture and energy gas storage. Up to now, extensive studies have been conducted based on UiO MOFs and their derivatives synthesized by functionalization/ modification on organic linkers. 10 Nevertheless, the gas sorption studies on UiO type MOFs incorporating Lewis basic pyridyl sites have never been investigated so far. The outstanding structural characteristics and excellent stability of UiO type MOFs motivate us to incorporate the pyridyl moieties into the frameworks, with the anticipation that it would further enhance the gas uptake capacities by anchoring the Lewis basic sites onto the pore surface but without sacrificing its original high porosity and exceptional robustness. He...

Concentration Dependent Dimensionality of Resonance Energy Transfer in a Postsynthetically Doped Morphologically Homologous Analogue of UiO-67 MOF with a Ruthenium(II) Polypyridyl Complex

“…31 As a consequence, a number of reports have emerged demonstrating post-synthetic metalation of UiO-67-DCBPY by a variety of different metals and metal complexes. 32,33 These presumably coordinate to the DCBPY ligands of the MOF to form transition metal coordination complexes in situ incorporated directly into the backbone of the UiO-67 MOF.…”

Tuning the cavities of zirconium-based MIL-140 frameworks to modulate CO2adsorption

“…2c). 33 in which the substitution of bpdc ligands with bpydc led to an enhancement in the CO 2 uptake to 8.0 wt% at 1 bar and 293 K. 33 Considering the isostructural relationship between MIL-140C and MIL-140C-25, and their theoretical pore volumes, the enhanced CO 2 capacity of the latter can be attributed to the incorporation of the Lewis basic bipyridyl sites, and potentially the presence of missing-linker defects. In the present case, at 0.15 bar and 293 K, the CO 2 volumetric capacity decreased in the order MIL-140A- (Fig.…”

Nitrogen-doped porous carbons from bipyridine-based metal-organic frameworks: Electrocatalysis for oxygen reduction reaction and Pt-catalyst support for methanol electrooxidation

“…Since bpdc contains two donor sites, it can connect three metal centers. However, some hard metal ions such as lanthanide or early transition metals prefer to bind bpdc only via the oxygen atoms in bpdc [35,36]. In contrast, Zn (II), a borderline Lewis acid, is coordinated by both the O and N atoms as shown in some complexes that bpdc act as ligand [37].…”