Zhibao Li

High and selective CO2 uptake, H2storage and methanol sensing on the amine-decorated 12-connected MOF CAU-1

The amine-decorated microporous metal–organic framework CAU-1 was readily synthesized and activated using a home-made efficient protocol. It exhibited a high heat of adsorption for CO2, high CO2 uptake capacity, and an impressive selectivity for CO2 over N2. At 273 K and up to 1 atm, CO2 uptake capacity can reach as much as 7.2 mmol g−1. Comparatively, the CH4 and N2 uptakes at 273 K and 1 atm were only 1.34 mmol g−1 and 0.37 mmol g−1, respectively. The CO2/N2 selectivity was 101 : 1 at 273 K. The isosteric heat of adsorption (Qst) for CO2 was ∼48 kJ mol−1 at the onset of adsorption, and it decreases to ∼28 kJ mol−1 at higher CO2 pressures. Furthermore, CAU-1 can adsorb 2.0 wt% and 4.0 wt% hydrogen at 77 K under 1 atm and 30 atm, respectively. The adsorption characteristics of CAU-1 for methanol investigated in situ with a quartz crystal microbalance (QCM), indicated that this particular MOF structure can be used as a highly sensitive sensor for methanol detection such as direct methanol fuel cells.

Mesoporous metal–organic frameworks: design and applications

Metal–organic frameworks (MOFs), which are constructed from the assembly of organic ligands with metal ions or metal clusters, have high potential applications in the fields of gas storage, separations and catalysis. MOFs involving mesopores are considered to have specific performance in such fields. In this mini review, we are mainly focussing on the recent developments in mesoporous MOFs including the design strategies and their most important applications.

Enhanced selectivity of CO2 over CH4 in sulphonate-, carboxylate- and iodo-functionalized UiO-66 frameworks

Three new functionalized UiO-66-X (X = -SO(3)H, 1; -CO(2)H, 2; -I; 3) frameworks incorporating BDC-X (BDC: 1,4-benzenedicarboxylate) linkers have been synthesized by a solvothermal method using conventional electric heating. The as-synthesized (AS) as well as the thermally activated compounds were characterized by X-ray powder diffraction (XRPD), diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, thermogravimetric (TG), and elemental analysis. The occluded H(2)BDC-X molecules can be removed by exchange with polar solvent molecules followed by thermal treatment under vacuum leading to the empty-pore forms of the title compounds. Thermogravimetric analysis (TGA) and temperature-dependent XRPD (TDXRPD) experiments indicate that 1, 2 and 3 are stable up to 260, 340 and 360 °C, respectively. The compounds maintain their structural integrity in water, acetic acid and 1 M HCl, as verified by XRPD analysis of the samples recovered after suspending them in the respective liquids. As confirmed by N(2), CO(2) and CH(4) sorption analyses, all of the thermally activated compounds exhibit significant microporosity (S(Langmuir): 769-842 m(2) g(-1)), which are comparable to that of the parent UiO-66 compound. Compared to the unfunctionalized UiO-66 compound, all the three functionalized solids possess higher ideal selectivity in adsorption of CO(2) over CH(4) at 33 °C.

Nanosized Cu-MOFs induced by graphene oxide and enhanced gas storage capacity

Various MOFs with tailored nanoporosities have recently been developed as potential storage media for CO2 and H2. The composites based on Cu-BTC and graphene layers were prepared with different percentages of graphene oxide (GO). Through the characterization analyses and gas adsorption experiments, we found that the nanosized and well-dispersed Cu-BTC induced by the incorporation of GO greatly improved the carbon dioxide capture and hydrogen storage performance of the composites. The materials obtained exhibited about a 30% increase in CO2 and H2 storage capacity (from 6.39 mmol g−1 of Cu-BTC to 8.26 mmol g−1 of CG-9 at 273 K and 1 atm for CO2; from 2.81 wt% of Cu-BTC to 3.58 wt% of CG-9 at 77 K and 42 atm for H2). Finally, the CO2/CH4 and CO2/N2 selectivities were calculated according to single-component gas sorption experiment data.