Xudong Hou

Porous Liquid: A Stable ZIF-8 Colloid in Ionic Liquid with Permanent Porosity

We reported an example of metal-organic framework (MOF)-based porous liquid by dispersing ZIF-8 ({Zn(mim)2}, mim = 2-methylimidazole) nanocrystallites in ionic liquid (IL) of [Bpy][NTf2] ( N-butyl pyridinium bis(trifluoromethyl sulfonyl)imide). Two essential challenges, stable colloid formation and porosity retention, have been overcome to prepare MOF-based porous liquid. Preventing ZIF-8 nanocrystals from aggregation before dispersing is vital to form a stable ZIF-8 colloid in IL via enhancing the interaction between ZIF-8 and IL. The resultant ZIF-8-[Bpy][NTf2] colloid is able to be stable over months without precipitating. [Bpy][NTf2] with larger ion sizes cannot occupy pores in ZIF-8, leaving the ZIF-8 cage empty for enabling access by guest molecules. The porosity of this porous liquid system was verified by positron (e+) annihilation lifetime spectroscopy and I2 adsorption in ZIF-8 in the colloid. MOF-based porous liquids could provide a new material platform for liquid-bed-based gas separations.

One-Step Synthesis of Dicyanobenzene-Derived N-doped Porous Carbon Monolayers: Porosity and NIR Photoactivity

We present a facile and one‐step synthesis of a N‐doped porous carbon (NPC) material by direct heating of dicyanobenzene in the presence of ZnCl2, free from any pre‐ or post‐treatment. The resultant NPC material features graphite‐like monolayers with a thickness of approximately 1.4u2005nm, as proven by microscopy technology. NPC shows a BET surface area of 3038.5u2005m2u2009g−1 and a narrow pore‐size distribution centered at 0.51u2005nm. As a consequence, NPC displays a high H2 uptake of up to 2.96u2005wtu2009% at 77u2005K and a CO2 adsorption capability of 23.4u2005wtu2009% at 278u2005K and 0.1u2005MPa. N‐doping leads to extension of the optical absorption of NPC into the near‐infrared (NIR) region. This N‐decorated carbon material, as the first example of a NIR‐triggered carbon photocatalyst, exhibits pronounced H2 production capabilities. Carbonization of aromatic multinitriles would be a general and facile approach to prepare multifunctional N‐doped carbon materials for gas storage and full solar spectrum driven photocatalysts.

Superficial Chiral Etching on Achiral Metal–Organic Framework for Enantioselective Sorption

Chiral recognition and separation is of general research interests in natural product separation and the pharmacy industry. In this work, we develop a novel strategy to modify achiral porous metal-organic framework (MOF) surfaces via a superficial chiral etching process (SCEP), in which reacting a presynthesized achiral MOF with a chiral ligand produces an achiral@chiral MOF core-shell hybrid composition. SCEP creates chiral species on an achiral porous MOF surface but does not change the porosity and pore structure, enabling core-shell composition enantioselective sorption. Reacting (+)-camphoric acid, (+)-Cam, and 1,4-diazabicyclo[2.2.2]octane (Dabco) with [Cu3(Btc)2] microcrystals leads to a chiral MOF of [Cu2((+)-Cam)2Dabco] crystallites attached on the surface of [Cu3(Btc)2] (Btc = 1,3,5-benzenetricarboxylate). The resulting [Cu3(Btc)2]@[Cu2((+)-Cam)2Dabco] core-shell composition displays preferred sorption kinetics toward (S)-limonene against (R)-limonene, with a similar discrimination effect with pure chiral [Cu2((+)-Cam)2Dabco]. Superficial chiral etching of the porous achiral MOF represents an economic and efficient strategy for enantioselective separation.

Green emission of indium oxide via hydrogen treatment

In this work, we prepared hydrogen treated indium oxide (H2-In2O3) and investigated the effect of hydrogen treatment on the optical and photoluminescence properties of In2O3. Hydrogen treatment has no influence on the crystal structure, but alters the intrinsic electronic structure and optical properties via introducing hydrogen induced defects such as shallow donor states (near the conduction band) and singly ionized oxygen vacancies in H2-In2O3. Both air-In2O3 (air calcinated) and H2-In2O3 show intense blue emission under UV excitation (280 nm). However, hydrogen treated In2O3 exhibited an additional green emission, which is absent in air-In2O3. This green emission arises from the passivation of singly ionized oxygen vacancies by hydrogen treatment. Hydrogen treatment could be a promising strategy to tune the electronic and optical properties of In2O3.

Exfoliating Polyoxometalate-Encapsulating Metal-Organic Framework into Two-Dimensional Nanosheets for Superior Oxidative Desulfurization

We report the exfoliation of two‐dimensional polyoxometalate‐encapsulating MOF (POM−Co‐MOF) into atomically thick nanosheets for highly efficient desulfurization application. Two‐dimensional layer‐structured MOF [Co2(H2O)4(BTX)3][PMo12O40] (BTX=1,4‐Bis(1,2,4‐triazol‐1‐ylmethyl)benzene) is featured with Keggin‐type POM wrapped in MOF skeleton via coordinating to cobalt with terminal oxygen. Wet ball‐milling and sonication assisted top‐down exfoliation in acetonitrile successfully delaminates POM‐MOF into nanosheets, which creates more accessible active sites and efficiently decreases the restriction of mass transfer during the reaction, and thus enhances the desulfurization efficiency. In comparison with bulk POM‐MOF, delaminated nanosheets exhibit a 14‐fold higher desulfurization efficiency via monitoring dibenzothiophene oxidation process (TON value of ca. 400) using H2O2 as oxidant. Meanwhile, POM−Co‐MOF nanosheets also show superior desulfurization performance in model oil system.

Conductive and Chiral Polymer-Modified Metal–Organic Framework for Enantioselective Adsorption and Sensing

We reported integration of conductivity, chirality, and porosity into MIL-101@chiral-PANI composite for synchronous chiral recognition, adsorption, and sensing toward enantiomers. The core-shell structure of MIL-101@chiral-PANI was characterized in detail by Fourier transform infrared and circular dichroism spectroscopy as well as scanning electron microscopy and transmission electron microscopy. Adsorption behaviors of carvone enantiomers over chiral PANI and MIL-101@chiral-PANI are satisfied with pseudo-first-order fitting. In comparison with chiral PANI, MIL-101@c-PANI exhibits a better enantioselectivity and much higher (>5-fold) adsorption amount over l-carvone than d-carvone. And MIL-101@c-PANI is able to recognize the chirality of carvone via electrochemical sensing, taking advantage of the electric conductivity of chiral PANI. Our result demonstrated the feasibility of applying achiral MOF for enantioselective sensing and adsorption via installing chiral and conductive gates. And this chiral polymer modification strategy represents a universal way to entitle achiral MOFs with chiral functions.