Sensing Properties of NH2-MIL-101 Series for Specific Amino Acids via Turn-On Fluorescence.

Metal-organic frameworks (MOFs) have been demonstrated to be desired candidates for sensing definite species owing to their tunable composition, framework structure and functionality. In this work, the NH2-MIL-101 series was utilized for sensing specific amino acids. The results show that cysteine (Cys) can significantly enhance the fluorescence emission of NH2-MIL-101-Fe suspended in water, while NH2-MIL-101-Al exhibits the ability to sense lysine (Lys), arginine (Arg) and histidine (His) in aqueous media via turn-on fluorescence emission. Titration experiments ensure that NH2-MIL-101-Fe and NH2-MIL-101-Al can selectively and quantitatively detect these amino acids. The sensing mechanism was examined and discussed. The results of this study show that the metal centers in MOFs are crucial for sensing specific amino acids.

An iron-nitrogen doped carbon and CdS hybrid catalytic system for efficient CO2 photochemical reduction.

Iron porphyrin and carbon black (CB) were utilized to fabricate an iron-nitrogen doped carbon (Fe-N-C) catalyst to create a new heterogeneous catalytic system with CdS to drive CO2 reduction to CO under UV/vis light (AM 1.5G) irradiation. The system delivers a high CO production yield of 111 mmol gcat-1 and a large turnover number (TON) of 1.22 × 103 in 8 h with a selectivity of 85%, all of which are competitive with state-of-the-art systems. The mechanism of the system was investigated by experimental and theoretical methods indicating that the high affinity between the iron active center and the *COOH intermediate facilitates the brilliant catalytic performance. This work provides a new direction for constructing heterogeneous CO2 photoreduction systems.

Coordination polymers with a pyridyl-salen ligand for photocatalytic carbon dioxide reduction.

A new ligand H2L with pyridine and salen moieties and its coordination polymers (CPs) [Mn(L)Cl]·DMF (1) and [Fe(L)Cl]·DMF (2) were synthesized and their photocatalytic activity for the conversion of CO2 into CO under visible-light irradiation was investigated. This is the first instance of pyridyl-salen-ligand based CPs for photocatalyzing CO2 reduction.

Cucurbit[7]uril-Based Metal-Organic Rotaxane Framework for Dual-Capture of Molecular Iodine and Cationic Potassium Ion.

Metal-organic rotaxane frameworks (MORFs) attracted much attention in the past years for construction of intelligent functional materials. Herein, a one-pot synthesis is reported of a three-dimensional (3D) cucurbit[7]uril (Q[7])-based MORF under hydrothermal conditions, namely Q[7]-MORF-1, formed by encapsulating the anionic benzoate moieties of the tricarboxylate ligand into the cavity of Q[7]. Furthermore, Q[7]-MORF-1 shows dual-capture capacity for iodine and K+ selectively among the alkali metal ions. The captured molecular iodine is included in the cavity of Q[7] through halogen-bonding interactions and the K+ cations are positioned at the carbonyl port of the Q[7] through K-O coordination interactions.

Solvent-Free Photoreduction of CO2 to CO Catalyzed by Fe-MOFs with Superior Selectivity.

It is deemed as a desired approach to utilize solar energy for the conversion of CO2 into valuable products, and the majority of the MOFs-based photocatalytic reductions of CO2 have focused on formic acid (HCOOH) production with an organic solvent as the reaction medium. Herein, we report a solvent-free reaction route for the photoreduction of CO2 catalyzed by Fe-MOFs, namely, NH2-MIL-53(Fe) [(Fe(OH)(NH2-BDC)]•G, NH2-MIL-88B(Fe) [Fe3O(H2O)3(NH2-BDC)3]Cl•G, and NH2-MIL-101(Fe) [Fe3O(H2O)3(NH2-BDC)3]Cl•G (NH2-BDC = 2-aminoterephthalic acid; G = guest and/or solvent molecules). Compared with the orthodox reaction route, the present out-of-the-way photocatalytic reduction of CO2 with superior selectivity to CO occurs at the gas-solid interface. The reaction procedure is environmentally friendly and provides a possibility to address the CO2 emission problem. Importantly, NH2-MIL-101(Fe) shows the highest photocatalytic activity among these Fe-MOFs due to its efficient charge separation and electron transfer.

Different functional group modified zirconium frameworks for the photocatalytic reduction of carbon dioxide.

Conversion of carbon dioxide (CO2) into useful chemicals is an important and urgent task from the energy and environment perspective. Herein, through a post-synthetic modification (PSM) approach, we synthesized three new metal-organic frameworks (MOFs) UiO-68-PSMs with different functional groups, namely, UiO-68-F, UiO-68-CH3 and UiO-68-OCH3, for the photocatalytic reduction of CO2. By introducing electron-withdrawing and electron-donating groups, UiO-68-PSMs showed different performance for the selective photocatalytic reduction of CO2 to CO because of change in charge separation and band gap of UiO caused by the presence of different functional groups.