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...

This review provides an overview of crucial roles that MOFs have played in constructing non-noble ORR catalysts.

A novel nanoporous metal−organic framework NPC-4 with excellent thermal stability was assembled from 2,3,5,6-tetramethylbenzene-1,4-diisophthalate (TMBDI) and the paddle-wheel secondary building unit (Cu 2 (COO) 4 ). The porous structure comprises a single type of nanoscale cage (16 Å diameter) interconnected by windows (5.2 × 6.3 Å), which give a high pore volume. CH 4 (195−290 K), CO 2 (198−303 K), N 2 (77 K), and H 2 (77 K) adsorption isotherms were studied for pressures up to 20 bar. NPC-4 exhibits excellent methane and carbon dioxide storage capacities on a volume basis with very high adsorbate densities, under ambient conditions. Isobars were investigated to establish the relationship for adsorption capacities over a range of storage temperatures. The isosteric enthalpies of adsorption for both CH 4 and CO 2 adsorption did not vary significantly with amount adsorbed and were ∼15 and ∼25 kJ mol −1 , respectively. The adsorption/desorption kinetics for CH 4 and CO 2 were investigated and activation energies, enthalpies of activation, and diffusion parameters determined using various kinetic models. The activation energies for adsorption obtained over a range of uptakes from the stretched exponential kinetic model were 5.1− 6.3 kJ mol −1 (2−13.5 mmol g −1 ) for CO 2 and 2.7−5.6 kJ mol −1 (2−9 mmol g −1 ) for CH 4 . The activation energies for surface barriers and diffusion along pores for both CH 4 and CO 2 adsorption obtained from a combined barrier resistance diffusion model did not vary markedly with amount adsorbed and were <9 kJ mol −1 . Comparison of kinetic and thermodynamic parameters for CH 4 and CO 2 indicates that a surface barrier is rate determining at high uptakes, while intraparticle diffusion involving diffusion through pores, consisting of narrow windows interconnecting with nanocages, being rate determining at very low uptakes. The faster CH 4 intraparticle adsorption kinetics compared with CO 2 for NPC-4 was attributed to faster surface diffusion due to the lower isosteric enthalpy of adsorption for CH 4 .