Creating ordered two-dimensional (2D) metal–organic framework (MOF) nanomaterials is conducive to understanding the structure–property relationship for rationally designing high-efficiency electrocatalysts. However, the controllable synthesis of ultrathin MOF nanosheets with predesigned structures and anticipative properties is still a great challenge. Here, we reported an electrolyte-assisted electrochemical approach to in situ exfoliate the intrinsic 2D MOF crystals with the Ni4Ln cluster as a secondary building unit (SBU) into ultrathin metal–organic nanosheets. Notably, the electric current density of the oxygen evolution reaction rapidly increases from 9.4 to 31.0 mA cm–2 at 1.8 V and the Tafel slope reduces from 150 to 87 mV dec–1, originating from electrochemically delaminating the thick 2D MOF precursors into ultrathin (∼4 nm) nanosheets to expose more catalytic active sites. Furthermore, the electrocatalytic oxygen evolution reaction (OER) activity of these 2D heterometallic MOF nanosheets can be effectively manipulated through precisely altering the lanthanide component of the Ni4Ln SBU in the layered MOFs. Density functional theory calculations reveal that the lanthanide ion of the SBU affects the adsorption and desorption capacity of active nickel centers to OER-relevant species, leading to the difference of the catalytic activity.

Three one‐dimensional ladder‐like coordination polymers consisting of Cd6 metalloring as the building unit, {[Cd4LCl4]·3H2O}n (1), {[Cd3L(ClO4)(H2O)]ClO4·3H2O}n (2), and {[Cd6(L)2(NO3)2(CH3OH)(H2O)](NO3)2·2CH3OH·5H2O}n (3), were solvothermally constructed from a carboxylic functionalized bisazamacrocyclic ligand 4,4′‐bis((4,7‐bis(2‐carboxyethyl)‐1,4,7‐triazacyclonon‐1‐yl)methyl)‐1,1′‐biphenyl (H4L). These compounds dispersed in ethanol show the multiple emissions originating from the monomeric and intramolecularly overlapping biphenyl moieties which could be sensitively quenched by picric acid (PA) and 4‐nitrophenol (4‐NP) through the effective fluorescence resonance energy transfer process. The differential fluorescent responses of each compound on exposure to PA and 4‐NP individually make the convenient ratiometric discrimination of two analytes based on the fluorescent intensity ratio (I320/I360) attainable, and 1 and 2 as ratiometric chemosensors for PA present a broad linear detection range from 4 to 300 μM with detection limits of 0.84 and 0.93 μM, respectively. Furthermore, the blue light emission of 1 under an ultraviolet lamp could be selectively quenched by PA even in the presence of all other interfering nitroaromatic pollutants, which empowers the fast visual detection of PA by naked eye.

Understanding the structure-property relationship of catalysts is the key to designing and manufacturing catalysts with high chemical activity and durability. [1][2][3][4] Since the active sites on the surface of heterogeneous catalysts cannot be clearly defined and quantified in contrast to their homogeneous opponents, as a result, the blossom in the realm of heterogeneous catalysis is often hindered by the difficulty of identifying the active sites on the catalyst surface. [5][6][7][8][9] The situation becomes more complicated especially when the surface of catalysts featuring versatile potential active sites or multiple catalytical active sites cooperate to promote a transformation process. [10][11][12][13] Although many available in situ and ex situ experimental techniques along with computational methods have been developed to solve these puzzles, sometimes the clear and accurate identification of active sites on the catalysts is still a challenging task. [14][15][16][17][18] In addition, how to quantitatively graft the highly active catalytic sites to the certain lattice positions of the solid catalyst to achieve high-efficient catalysis is another huge challenge for rational design and synthesis of heterogeneous catalysts with excellent performance. [19][20][21] Metal-organic frameworks (MOFs) are an important class of inorganic-organic hybrid porous materials featuring the characteristics of the tailorable structure, easy characterization, high specific surface area, and adjustable pore size. [22,23] These advantages not only bestow MOFs with the potential to be high-performance catalysts, but also make them the ideal platform for studying the structure-property relationships. [24][25][26][27] Furthermore, highly active sites can be introduced into the specific lattice positions during the construction of MOFs-based catalysts by direct solvothermal synthesis or post-synthetic methods (including post-synthetic modification, post-synthetic protection, and post-synthetic exchange) to boost the catalytic activity. [28][29][30] However, the thermal or chemical stability of most MOFs under catalytic conditions is usually poor, which limits their practical application. [31,32] The mixed-nickel and iron oxide/oxyhydroxide (NiFeO x H y ) nanosheets are a kind of inorganic layered compound composed of main layer and interlayer anions, where the bivalent or trivalent nickel/iron ions in the main layer coordinate with anionic

Two cyclen-based multidentate N,O ligands, 1,4,7,10-tetrazazcyclododecane-N, N 0 ,N 00 ,N 000 -tetra-p-methylbenzoic acid (H 4 L 1 ) and 1,4,7,10-tetrazazcyclododecane-N,N 0 ,N 00 ,N 000 -tetra-p-cinnamic acid (H 4 L 2 ), were reacted with Zn (II) salts leading to a four-fold interpenetrated 3D binodal PtS-type network {[Zn 2 (HL 1 ) Cl]Á5H 2 O} n (Zn-1) along with a 1D ribbon-like polymeric chain {[Zn 3 (HL 2 ) Cl 3 (H 2 O) 2 ]Á2CH 3 COCH 3 Á3H 2 O} n (Zn-2). Both two compounds exhibited excellent water stability in a wide pH range from 2 to 12 and emitted either UV or visible blue-purple light. They can behave as recyclable fluorescent probes for highly selective sensing of nitrophenols with low detection limits. Additionally, the blue-purple emission of Zn-2 can be efficiently quenched by PA with a concentration as low as 20 μM; thus, the naked-eye detection of PA can be fulfilled under a 365 nm UV lamp. Based on the DFT calculation and spectral analysis evidences, it can be proposed that the selective detection of nitrophenols by two Zn (II) compounds is owing to a synergistic effect of different quenching mechanisms along with the interactions between probes and analytes.