Qi-Kui Liu

Highly efficient iodine species enriching and guest-driven tunable luminescent properties based on a cadmium(II)-triazole MOF.

The first example of highly efficient iodine enrichment based on a Cd(II)-triazole MOF (1) via both molecular sorption and ion-exchange approaches is reported.

Encapsulation of Ln3+ hydrate species for tunable luminescent materials based on a porous Cd(II)-MOF

This work builds on the recently developed guest-driven approach for the construction of tunable luminescent materials based on porous metal–organic frameworks (MOFs). The porous heteroatom-rich Cd(II)-MOF (1) material has been obtained by the reaction of Cd(NO3)2 with 3,5-bis(3-carboxyphenyl)-1,2,4-triazole)/4,4′-bis(4-pyridyl)ethane in solution. Compound 1 features (4,4) sheets which interlock together to generate a 2-fold interpenetrating robust framework containing ellipse-like channels with pore dimensions of ca. 9 × 11 A. In particular, 1 is able to trap lanthanide hydrate cationic species such as Eu(H2O)83+ and Tb(H2O)83+ and to sensitize their emissions in the solid state. Furthermore, the emission colors could be tuned by changing the co-doped Eu3+/Tb3+ ratio in the Cd(II)-MOF to provide barcode-like luminescent materials.

Independent 1D nanosized metal-organic tube: anion exchange, separation, and anion-responsive luminescence.

Three independent 1D metal-organic nanotubes AgL(2)X(2) [X = PF(6)(-) (1), ClO(4)(-) (2), and SbF(6)(-) (3)] with anion exchange, separation, and anion-responsive photoluminescence are reported.

Copper(I) Metal–Organic Framework: Visual Sensor for Detecting Small Polar Aliphatic Volatile Organic Compounds

A porous Cu(I)-MOF [H2O⊂Cu2(L)2I2; L = 1-benzimidazolyl-3,5-bis(4-pyridyl)benzene], which can be a visual and luminescent sensor for detecting small polar aliphatic volatile organic compounds (VOCs), such as alcohols, ketones, and halocarbons, is reported. The naked-eye and luminescent detection limitations for these VOCs are 5 and 1 ppm, respectively.

Co(II)-MOF: A Highly Efficient Organic Oxidation Catalyst with Open Metal Sites

A porous Co(II)-MOF (1) was synthesized by the combination of a bent imidazole-bridged ligand and p-phthalic acid (PTA) with Co(OAc)2 under solvothermal conditions. This Co(II)-MOF (1) is able to undergo a reversible MeOH substitution reaction on the Co(II) center via a single-crystal-to-single-crystal process. The desolvated Co(II)-MOF (2) with the open Co(II) sites is very stable (up to 350 °C). Furthermore, 2 is a highly active heterogeneous catalyst for various organic substrates oxidation in the presence of tert-butyl hydroperoxide (TBHP) under milder conditions. The importance of open Co(II) sites in 2 for the organic substrates oxidation is directly evidenced by the single-crystal X-ray diffraction.

A porous Cd(II)-MOF-coated quartz fiber for solid-phase microextraction of BTEX

The utilization of a porous Cd(II)-MOF ([Cd(L)2(ClO4)2]·H2O) (L = 4-amino-3,5-bis(4-pyridyl-3-phenyl)-1,2,4-triazole) with good thermal/chemical stability for solid-phase micro-extraction (SPME) is reported. The Cd(II)-MOF thin films are expediently in situ grown on quartz fiber in solution, exhibiting high sensitivity and selectivity towards volatile benzene, toluene, o-, m-, p-xylene, and ethylbenzene (termed as BTEX) aromatics. The limits of detection for BTEX are 0.01–0.001 μg L−1.

Cd(II)-MOF: adsorption, separation, and guest-dependent luminescence for monohalobenzenes.

A series of isostructural 2-fold interpenetrating 2D Cd(II)-MOFs, namely G⊂CdL2(OTs)2 (G = THF (1), PhF (2), PhCl (3), PhBr (4), PhI (5), L = 1,2-bis[(3-(pyridin-4-yl)phenoxy]ethane, and OTs(-) = p-toluenesulfonate anion), have been successfully synthesized from the flexible ethylene glycol ether-bridging ligand L and Cd(OTs)2 in solution. The CdL2(OTs)2 framework contains squarelike nonpolar channels, and the encapsulated guest molecules can be removed by heating (150 °C) to generate a guest-free host framework which is able to reversibly adsorb monohalobenzenes PhX (X = F, Cl, Br, I) in the liquid phase under ambient conditions without loss of framework integrity. Furthermore, it can effectively separate these monohalobenzenes and exhibits a clear affinity for monohalobenzenes according to the following order: PhI > PhBr > PhCl > PhF. In addition, PhX⊂CdL2(OTs)2 exhibits guest-dependent luminescence properties.

A self-assembled Pd6L8 nanoball for Suzuki–Miyaura coupling reactions in both homogeneous and heterogeneous formats

A self-assembled nano-sized Pd6L8 (L = 1,3,5-tris(4′-pyridyloxadiazole)-2,4,6-triethylbenzene) ball was constructed based on a new oxadiazole-containing tripod. In H2O–EtOH mixed-solvent system, Pd(II)-ball displays excellent performance in Suzuki–Miyaura cross-coupling reactions at low catalyst loading under ambient conditions in a homogeneous fashion. Furthermore, it shows heterogeneous catalyst nature in o-xylene and can be reused without loss of catalytic activity.

Fabrication of Cd(II)-MOF-based ternary photocatalytic composite materials for H2 production via a gel-to-crystal approach.

Cd(II)-MOF-based ternary composite materials of CdS@Cd(II)-MOF@TiO2 were prepared by a unique TiO2 induced gel-to-crystal approach. CdS@Cd(II)-MOF@TiO2 was demonstrated to be a highly active photocatalyst for hydrogen production under visible light based on water photolysis.

Reversible adsorption and separation of chlorocarbons and BTEX based on Cu(II)-metal organic framework

A new non-interpenetrating 2D Cu(II)-metal organic framework has been successfully synthesized from the carbazole-bridging organic ligand L and Cu(NO3)2 in solution. The CuL2(NO3)2 framework contains square-like channels and the n-butyl groups on L face toward the channel center to form the typical hydrophobic pores. In addition, the reported CuL2(NO3)2 host can reversibly upload various VOCs such as CH2Cl2, CHCl3 and BTEX (benzene, toluene, ethylbenzene, o-xylene, m-xylene, and p-xylene) under ambient conditions without loss of framework integrity. Furthermore, it is able to effectively separate CH2Cl2 from CHCl3, benzene from toluene/ethylbenzene/xylene and toluene from ethylbenzene/xylene in the liquid phase. The selectivity for chlorocarbons is derived from the substrate polarity, while the host–guest hydrophobic interaction might be the dominating factor for BTEX affinity.