ABSTRACT
Porous liquids are fluids with the permanent porosity, which can overcome the poor gas solubility limitations of conventional porous solid materials for three phase gas-liquid-solid reactions. However, preparation of porous liquids still requires the complicated and tedious use of porous hosts and bulky liquids. Herein, we develop a facile method to produce a porous metal-organic cage (MOC) liquid (Im-PL-Cage) by self-assembly of long polyethylene glycol (PEG)-imidazolium chain functional linkers, calixarene molecules and Zn ions. The Im-PL-Cage in neat liquid has permanent porosity and fluidity, endowing it with a high capacity of CO2 adsorption. Thus, the CO2 stored in an Im-PL-Cage can be efficiently converted to the value-added formylation product in the atmosphere, which far exceeds the porous MOC solid and nonporous PEG-imidazolium counterparts. This work offers a new method to prepare neat porous liquids for catalytic transformation of adsorbed gas molecules.
ABSTRACT
Metal N-heterocyclic carbenes (M-NHCs) on the pore walls of a porous metal-organic framework (MOF) can be used as active sites for efficient organic catalysis. Traditional approaches that need strong alkaline reagents or insoluble Ag2O are not, however, suitable for the incorporation of NHCs on the backbones of MOFs because such reagents could destroy their frameworks or result in low reactivity. Accordingly, development of facile strategies toward functional MOFs with covalently bound M-NHCs for catalysis is needed. Herein, we describe the development of a general and facile approach to preparing MOFs with covalently linked active M-NHC (M = Pd, Ir) single-site catalysts by using a soluble Ag salt AgOC(CF3)3 as the source and subsequent transmetalation. The well-defined M-NHC-MOF (M = Pd, Ir) catalysts obtained in this way have shown excellent catalytic activity and stability in Suzuki reactions and hydrogen transfer reactions. This provides a general and facile strategy for anchoring functional M-NHC single-site catalysts onto functionalized MOFs for different reactions.
ABSTRACT
The unique applications of porous metal-organic framework (MOF) liquids with permanent porosity and fluidity have attracted significant attention. However, fabrication of porous MOF liquids remains challenging because of the easy intermolecular self-filling of the cavity or the rapid settlement of porous hosts in hindered solvents that cannot enter their pores. Herein, we report a facile strategy for the fabrication of a MOF liquid (Im-UiO-PL) by surface ionization of an imidazolium-functionalized framework with a sterically hindered poly(ethylene glycol) sulfonate (PEGS) canopy. The Im-UiO-PL obtained in this way has a CO2 adsorption approximately 14 times larger than that of pure PEGS. Distinct from a porous MOF solid counterpart, the stored CO2 in Im-UiO-PL can be slowly released and efficiently utilized to synthesize cyclic carbonates in the atmosphere. This is the first example of the use of a porous MOF liquid as a CO2 storage material for catalysis. It offers a new method for the fabrication of unique porous liquid MOFs with functional behaviors in various fields of gas adsorption and catalysis.
ABSTRACT
A new strategy to prepare soluble homogeneous catalysts is developed by introducing imidazolium into cationic calix[4]arene-based metal-organic cages (MOCs). The soluble MOCs show high activity and recyclability in the cycloaddition reaction of CO2 without the addition of any co-catalysts. This method provides new inspiration to design highly efficient catalysts by combining the advantages of homogeneous and heterogeneous catalysis.
ABSTRACT
Three cationic capsule-shaped Zr-based metal-organic polyhedra (MOPs) with different cavity sizes were successfully constructed through the self-assembly of trinuclear zirconocene clusters and imidazolium-functionalized dicarboxylic ligands. Owing to the imidazolium groups in the MOPs, they show good CO2 adsorption uptake. Moreover, the halogen anions of the imidazolium groups and Brønsted acid sites (-OH) in the Zr-based knots are in close proximity, making these MOPs able to catalyze synergistically the cycloaddition reaction of CO2 with epoxides into cyclic carbonates. This is the first report of using MOPs as catalysts for this reaction without the addition of a cocatalyst.
ABSTRACT
An imidazolium-functionalized mesoporous cationic Cr-based metal-organic framework (MOF) with high densities of positive charges was synthesized for the first time via a mixed-solvent strategy. The cationic mesoporous Cr-based MOF showed excellent adsorption performances in the removal of dichromate Cr2O72- from water with a large uptake of 321 mg g-1 and good regeneration ability.
