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Selective CO2 adsorption and catalysis conversion of CO2 to high value-added chemicals not only gives an effective way to reduce the concentration of CO2 but also provides the precursors for industrial manufacturing of chemicals and fuels. With well-defined frameworks, flexible modifiability, and permanent porosity, metal–organic frameworks (MOFs) can be the ideal platforms for CO2 utilization applications. In this work, a copper functionalized-zirconium MOF, denoted Zr-CPB-Cu (CPB = 1,2,3,4,5,6-hexakis(4-carboxyphenyl)-benzene), was successfully produced via post-metalation of copper(II) ions into a presynthesized Zr-CPB MOF. The bimetallic Zr-CPB-Cu containing two open metal sites (Zr4+ and Cu2+), polarized groups (e.g., uncoordinated –COOH, monodentate carboxylates, and acetate anions), accessible triangular channels, and permanent porosity (SBET = 420 m2 g−1) revealed outstanding selective CO2 adsorption and catalytic activity for the oxidative carboxylation of CO2 and olefins. As a proof of concept, the Zr-CPB-Cu showed higher low-pressure capacities of CO2, CH4, and N2 at room temperature and larger CO2 selectivities over N2 and CH4 than those of the parent Zr-CPB. As for catalysis of CO2 conversion, the Zr-CPB-Cu catalyst exhibited exceptional performance in direct synthesis of styrene carbonate from styrene and CO2 with 97% conversion of styrene, and 92% yield of styrene carbonate in the presence of anhydrous TBHP oxidant and under mild conditions (1 atm of CO2, 80 °C, and 12 h). Notably, the catalytic activity of Zr-CPB-Cu outperformed that of the parent Zr-CPB and other MOFs, and the recovered Zr-CPB-Cu can be reused up to six times without considerable reduction in catalytic activity. Our result envisaged an effective approach for the elaboration of MOFs as efficient heterogeneous catalysts for CO2 separation and catalytic conversion of CO2. [ABSTRACT FROM AUTHOR]

The acylamide functionalized tetra-carboxylic acid (H4CDA) has been successfully employed for the formation of two robust 3D-MOFs, Cd-CDA-MOF and Cu-CDA-MOF, having open metal sites with two distinct and diverse network topologies namely diamondoid and PCU. The Cd-CDA-MOF is shown to act as an efficient heterogeneous catalyst for the Knoevenagel condensation reaction under mild and ambient conditions. The Cu-CDA-MOF demonstrates excellent catalytic activity for the Chan–Lam coupling reaction with a considerably high turnover number. The heterogeneous catalytic activity of the MOFs can be attributed to the coordinatively unsaturated open metal sites of the activated frameworks. The MOFs are found to be recyclable with almost uniform catalytic activity. [ABSTRACT FROM AUTHOR]

A non-porous version of SU-101 (herein n-SU-101) was evaluated for the CO2 cycloaddition reaction. The findings revealed that open metal sites (Bi3+) are necessary for the reaction. n-SU-101 displays a high styrene oxide conversion of 96.6% under mild conditions (3 bar and 80 °C). The catalytic activity of n-SU-101 demonstrated its potential application for the cycloaddition of CO2 using styrene oxide. [ABSTRACT FROM AUTHOR]

Building metal–organic frameworks (MOFs) covalently modified by onium halides is a promising approach to develop efficient MOF-based heterogeneous catalysts for the cycloaddition of CO2 to epoxides (CCE) into cyclic carbonates. Herein, we report a novel zirconium-based MOF covalently modified by methyl pyridinium bromide, Zr6O4(OH)4(MPTDC)2.2(N-CH3-MPTDC)3.8Br3.8 ((Br−)CH3-Pyridinium-MOF-1), where MPTDC denotes 3-methyl-4-pyridin-4-yl-thieno[2,3-b] thiophene-2,5-dicarboxylate. The structure and composition of this complex were fully characterized with PXRD, NMR, XPS, TEM and so on. CO2 adsorption experiments show that (Br−)CH3-Pyridinium-MOF-1 has a higher affinity for CO2 than its electrically neutral precursor, which should be attributed to the fact that charging frameworks containing pyridinium salt have stronger polarization to CO2. (Br−)CH3-Pyridinium-MOF-1 integrated reactive Lewis acid sites and Br− nucleophilic anions and exhibited efficient catalytic activity for CCE under ambient pressure in the absence of co-catalysts and solvents. Furthermore, (Br−)CH3-Pyridinium-MOF-1 was recycled after five successive cycles without substantial loss in catalytic activity. The corresponding reaction mechanism also was speculated. [ABSTRACT FROM AUTHOR]

Organic and inorganic building blocks are used to construct a class of metal–organic frameworks (MOFs) that exhibit tremendous chemical tunability. In this study, a novel zirconium-based MOF UiO-66-(alkyne)2 with a di-alkyne tag was obtained through solvothermal pre-synthesis, which provides a potential covalent binding site for post-synthesis modification. On this basis, a gentle post-synthesis modification strategy based on covalency was expanded for introducing diverse metals, and a family of isostructural tailored materials (UiO-66-alkyne-Co, UiO-66-(alkyne-Co)2 and UiO-66-(alkyne-Ni)2) with base metals Ni or Co were designed and synthesized successfully. Among them, di-alkyne tagged UiO-66-(alkyne-Co)2 has shown unprecedented remarkable performance as a heterogeneous catalyst for the Knoevenagel reaction, completely converting benzaldehyde in just 5 min at room temperature, to our knowledge, faster than the reported MOF catalysts. Moreover, UiO-66-(alkyne-Co)2 maintains high stability and functionality after five cycles, and the catalytic activity is also preserved in the gram level scale-up experiment, indicating that UiO-66-(alkyne-Co)2 has great potential for practical application in the formation of C–C bonds. In a sense, this research provides an ideal platform for anchoring the required functional groups on alkyne-modified MOFs, which lays a foundation for finding more potential applications of MOF materials in the future. [ABSTRACT FROM AUTHOR]

Two model porphyrin metal–organic frameworks were used for the incorporation of Rh(I) species by a post-synthetic metallation under mild conditions. As a result, new rhodium MOFs (Rh/MOFs), Rh/PCN-222 and Rh/NU-1102, were synthesized and structurally characterized. To illustrate the potential of this catalytic platform, we use Rh/MOFs as phosphine-free heterogeneous catalysts in the hydrogenation of unsaturated hydrocarbons under mild reaction conditions (30 °C and 1 atm H2). We found that for our Rh/MOFs an activation step is required during the first run of the catalytic process. The presence of Rh–CO moieties allowed us to monitor the activation pathway of the catalyst under a H2 atmosphere, by in situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). After activation, the catalyst remains highly active during the subsequent catalytic cycles. This simple post-synthetic modification approach presents new possibilities for the utilization of Rh-based catalytic systems with robust porphyrin-based MOFs as supports. [ABSTRACT FROM AUTHOR]

A novel polyoxovanadate-based copper(I)–organic framework, [CuI(bib)]4{VV4O12} (V–Cu–MOF, bib = 1,4-bis(1H-imidazoly-1-yl)benzene), is facilely synthesized under mild hydrothermal conditions. The structure of the V–Cu–MOF is constructed from a cyclic {V4O12}4− polyanion cluster and a 1D chain Cu(I)–MOF ([CuI(bib)]+). The presence of the {V4O12}4− cluster stabilizes the Cu(I)–MOF with Cu(I) as the center, thereby improving the stability of the V–Cu–MOF and enabling it to stably exist in various solvents and pH = 2–12 solutions. Additionally, the V–Cu–MOF as a heterogeneous catalyst can catalyze the carboxylative cyclization of CO2 and propargylic alcohols to high value-added α-alkylidene cyclic carbonates at room temperature, and the conversion and selectivity are almost 100%. More importantly, no obvious decrease in the yield of the α-alkylidene cyclic carbonate is observed after ten cycles. These results indicate the excellent catalytic activity and sustainability of the V–Cu–MOF. Research on the mechanism of the catalytic reaction suggests that the high-density Cu(I) sites in the V–Cu–MOF are the catalytically active centers for activating the C≡C bonds of propargylic alcohols. To the best of our knowledge, this is the first example of polyoxometalate-based metal–organic framework catalyst for catalyzing the conversion of CO2 to value-added α-alkylidene cyclic carbonates at room temperature. [ABSTRACT FROM AUTHOR]

The efficient and selective aerobic oxidation of alcohols has been investigated with judicious combinations of europium-incorporated and/or TEMPO ((2,2,6,6-tetramethylpiperidin-1-yl)oxyl)-functionalized zirconium-based porous metal–organic frameworks (MOFs). Although MOFs are well-known catalytic platforms for the aerobic oxidation with radical-functionalities and metal nanoparticles, these systematic approaches involving metal cations and/or radical species introduce numerous interesting aspects for cooperation between metals and TEMPO for the aerobic oxidation of alcohols. The role of TEMPO as the oxidant in the heterogeneous catalytic aerobic oxidation of alcohols was revealed through a series of comparisons between metal-anchored, TEMPO-anchored, and metal and TEMPO-anchored MOF catalysis. The fine tunability of the MOF allowed the homogeneously and doubly functionalized catalysts to undergo organic reactions in the heterogeneous media. In addition, the well-defined and carefully designed heterogeneous molecular catalysts displayed reusability along with better catalytic performance than the homogeneous systems using identical coordinating ligands. The role of metal-cation fixation should be carefully revised to control their coordination and maximize their catalytic activity. Lastly, the metal cation-fixed MOF displayed better substrate tolerance and reaction efficiencies than the TEMPO-anchored MOF or mixture MOF systems. [ABSTRACT FROM AUTHOR]

Incorporating catalytic units into a crystalline porous matrix represents a facile way to build high-efficiency heterogeneous catalysts, and by rational design of the porous skeleton with appropriate building blocks the catalytic performance can be significantly enhanced for a series of organic transformations owing to the synergistic effect from the multicomponent and confined porous microenvironment around catalytically active sites. Herein, we demonstrate that the design and synthesis of a porous polyoxometalate-based metal–organic framework YL2(H2O)2[CrMo6O18(PET)2]·4H2O (POMOF-1) constructed from Anderson-type [CrMo6O18(PET)2] (PET = pentaerythritol), which can be employed as a multifunctional platform for synthesis of N-containing compounds via selective oxidative coupling with amines. POMOF-1 features microporous 1D channels defined by Y3+ and L, with [CrMo6O18(PET)2] arranged orderly between adjacent Lvia electrostatic interactions. Upon using POMOF-1 as a catalyst and H2O2 as an oxidant, a variety of amines could be effectively converted to value-added amides, imines and azobenzenes via the oxidative cross-coupling with alcohols or homo-coupling. In particular, POMOF-1 showed dramatically improved activity for the N-formylation reaction owing to the synergistic and confinement effect, with the yield of amides up to 95% and 4 times higher than that of homogeneous [CrMo6O18(PET)2]. Meanwhile, the oxidative homo-coupling of arylmethylamines and arylamines can be facilely tuned by adjustment of the amount of oxidant, solvent and additive, affording imines and azobenzenes in high selectivity and yield, respectively. POMOF-1 is robust and can be reused for 5 cycles with little loss of catalytic activity and structural integrity. The work demonstrates that the combination of catalytically active POMs with crystalline porous MOFs holds great potential to build robust and recyclable heterogeneous systems with enhanced activity and selectivity for multifunctional catalysis. [ABSTRACT FROM AUTHOR]

A novel metal–organic framework (MOF) based on strontium alkaline-earth metal and 2-amino-1,4-benzenedicarboxylic acid (NH2-bdc) has been developed. This material is formed by a linear succession of face-sharing strontium polyhedra bridged by an organic ligand molecule to give a three-dimensional network with rhombohedral one-directional channels. This MOF is stable in polar organic solvents and up to 250 °C. The basic catalytic activity of both strontium metal nodes and amino groups of the ligand was tested in Knoevenagel condensation reactions. The influence of the temperature and reaction solvent over the catalytic performance of the MOF catalyst was demonstrated. The strontium/amino-containing MOF material evidenced a remarkable activity as compared to other conventional alkaline oxides typically used as reference basic solid catalysts. The novel MOF material showed remarkable activity and structural stability during five consecutive catalytic runs with no evidence of activity loss under the best reaction conditions found in this study. [ABSTRACT FROM AUTHOR]

A novel mixed-valence polyoxovanadate-based copper–organic framework, [CuI(bbi)]2{[CuI(bbi)]2V IV2 VV8O26}·2H2O (NENU-MV-5, bbi = 1,1′-(1,4-butanediyl)bis(imidazole)), was facilely synthesized from routine reagents under mild hydrothermal conditions. Using NENU-MV-5 as a heterogeneous catalyst without any co-catalyst, one-step oxidative cleavage of β-O-4 lignin into phenols and aromatic acids with high catalytic activity and selectivity was realized under an oxygen atmosphere. No obvious decrease in activity was observed after five cycles, which indicates the excellent stability and sustainability of NENU-MV-5. The perfect catalytic performance of NENU-MV-5 can be attributed to the multi-site synergistic effect of the mixed-valence VV–O–VIV sites on polyoxovanadate for the oxidation of β-O-4 alcohol to β-O-4 ketone and the Cu(I) sites on the framework for the rapid cleavage of the Cα–Cβ bond of β-O-4 ketone. This system represented the first co-catalyst-free example for the one-step selective degradation of lignin catalyzed by a well-defined crystalline catalyst with definite composition and structure in a single solvent. [ABSTRACT FROM AUTHOR]