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Developing efficient heterogeneous catalysts for chemical fixation of CO2to produce high-value-added chemicals under mild conditions is highly desired but still challenging. Herein, we first reported an approach to prepare a novel catalyst (Ag@NCNFs), featuring Ag nanoparticles (NPs) embedded within porous nitrogen-doped carbon nanofibers (NCNFs), via growing a Ag metal–organic framework on one-dimensional electrospun nanofibers followed by pyrolysis. Benefiting from the abundant nitrogen species and porous structure, Ag NPs is well dispersed in the obtained Ag@NCNFs. Catalytic studies indicated that Ag@NCNFs exhibited excellent catalytic activity for the three-component coupling reaction of CO2, secondary amines, and propargylic alcohols to generate β-oxopropylcarbamates under mild conditions with a turnover number (TON) of 16.2, and it can be recycled and reused at least 5 times without an obvious decline in catalytic activity. The reaction mechanism was clearly clarified by FTIR, NMR, 13C isotope labeling, control experiments, and density functional theory calculations. The results suggest that Ag@NCNFs and 1,8-diazabicyclo[5.4.0]undec-7-ene can synergistically activate propargylic alcohol to react with CO2, and then the generated α-alkylidene cyclic carbonate was invaded by secondary amine to produce β-oxopropylcarbamate. Importantly, to the best of our knowledge, this is the first experimental and theoretical investigation on this reaction.

Four new and interesting Ln4clusters formulated as [Ln4(NO3)2(acac)4(HL1)2(CH3OH)2]·2(CH3CN)] (Ln = Gd(1), Dy(2); H4L1 = 2-(hydroxymethyl)-2-(((2-hydroxynaphthalen-1-yl)methylene)amino)propane-1,3-diol); acac = acetylacetone) and [Ln4(NO3)2(acac)4(L2)2(CH3CH2OH)2] (Ln = Gd(3), Dy(4); H3L2 = 2-(((2-hydroxynaphthalen-1-yl)methylene)amino)-2-methylpropane-1,3-diol; acac = acetylacetone) were designed and constructed. Single-crystal X-ray studies indicate that all clusters have a defect dicubane topology in which four Ln(III) are on a plane bond with an arrangement of a parallelogram with the μ3-O bridge. The difference between the two series of clusters lies in the change of the ligand substituent and terminal coordinated solvent molecules. All Ln(III)-based clusters 1–4have exhibited excellent solvent stability. The magnetic investigation suggests that clusters 1and 3possess a different magnetothermal effect (−ΔSm= 35.24 J kg–1K–1for 1, and −ΔSm= 36.68 J kg–1K–1for 3). In addition, the diversity in the environment of the metal center leads to the distinct dynamic behavior of Ueff/kB(21.27 K for 2and 1.96 K for 4) and τ0(1.43 × 10–7s for 2and 2.43 × 10–6s for 4). More importantly, clusters 1–4as heterogeneous catalysts can efficiently catalyze the reaction of CO2with bromopropylene oxide and aromatic amine to synthesize oxazolidinones under mild conditions. By comparison, clusters 1and 2show higher catalytic activity than 3and 4, in which the Brønsted acidic −OH groups working together with Lewis acid metal sites improve the catalytic activity of Ln(III)-based clusters 1and 2. To the best of our knowledge, it is the first example of Ln(III)-based clusters that show good magnetic property and high catalytic activity simultaneously by regulating the coordination environment of Ln(III) ions. Our work provided a promising direction for regulating properties of multifunctional polynuclear Ln(III)-based clusters via changing the coordinated environment of the metal center. It also helps inspire the development of polynuclear Ln(III)-based multifunctional materials.

A series of bifunctional Ln(III)-based coordination polymers (CPs) {Ln(L)(DMA)2(NO3)}n[Ln(III) = Eu (1), Gd (2), and Dy (3); organic ligand H2L = 2,2′-(1,3,5,7-tetrahydroxyoctahydro-4,8-ethanopyrrolo[3,4-f]isoindole-2,6(1H,3H)-diyl)diacetic acid)] have been successfully synthesized. CPs 1–3are isostructural and constructed from the dimeric Ln2unit in which two adjacent LnIIIions are bridged by two μ3-carboxyl oxygens, and the Ln2dimeric unit is connected by two NO3–ions, four DMA molecules, and four completely protonated L2–ligands forming a 2D layer structure. The magnetic research reveals that CP 2shows a significant cryogenic magnetocaloric effect (−ΔSm= 22.9 J kg–1K–1; T= 2.0 K and ΔH= 7.0 T), whereas CP 3exhibits slow magnetic relaxation property under Hdc= 0 Oe field. Additionally, the luminescence explorations revealed that CP 1can act as a recyclable luminescent probe for pollutant acetylacetone among various small organic solvent molecules, and the corresponding detection limit is 10–7mol/L. More importantly, CP 1also exhibits good catalytic performance in the cycloaddition reaction of CO2and epoxides or cyanamides under mild conditions. As far as we know, CP 1represents the first bifunctional lanthanide homogeneous catalyst that can efficiently catalyze the reaction of cyanamides/epoxides with CO2simultaneously.

A series of new Ln8clusters [Ln8(acac)4(HL)4(L)2(μ3-O)4(C2H5O)4]·2C2H5OH·2CH2Cl2(Ln(III) = Gd (1), Dy (2), and Ho (3); Hacac = acetylacetone and H2L = 2-hydroxy-benzoic acid (5-hydroxymethyl-furan-2-ylmethylene)-hydrazide) have been designed and constructed using a multiple coordination site Schiff base ligand (H2L) as  well  as a β-diketonate auxiliary ligand.  The structures, magnetic properties, and catalytic performance of clusters 1–3have been studied. X-ray crystallography data revealed that clusters 1–3possess similar structures with two chair-form Ln4cores bridged by four μ3-O atoms. Clusters 1–3display extensive and high solvent stability. Magnetic analysis exhibits that cluster 1possesses a comparably large magnetocaloric effect (−ΔSm= 33.06 J kg–1K–1at 2.0 K and 7.0 T). AC susceptibility measurement suggests that cluster 2exhibits single-molecule magnet behavior under zero-field conditions. What’s more, all clusters can effectively convert CO2with epoxides. The highest yield is 98% at 70 °C 0.1 MPa catalyzed by 1. In addition, cluster 1can be reused three times with a negligible loss of catalytic activity.