Nanoporous Zn^II/Tb^III–Organic Frameworks for CO₂ Conversion

Abstract

Zn II Tb III (CO 2 ) 3 (H 2 O)] clusters and the desigened bifunctional ligand of H 6 TDP engendered one highly robust anionic), which featured two types of nanochannels decorated with density open metal sites and free oxygen atoms on the wall. To the best our knowledge, NUC-7 represented one novel kind of heterometallic Zn II /Ln III -organic 3D honeycomb MOFs with exposed tetra-coordinated Zn II -metal sites as Lewis acid sites. Subsequent studies indicated that NUC-7 could highly adsorb CO 2 and catalyze the cycloaddition of various epoxides into related carbonates with the help of cocatalyst TBAB under lukewarm conditions of 1 atm and 80 °C. Meanwhile, NUC-7 exhibited the effectively selective sensitivity for discriminating Fe 3+ in aqueous solution by luminescence quenching. It could be inferred that the excellent characteristics including large void volume, high porosity, active open metal sites, and uncoordinated carboxylate oxygen atoms as Lewis acid and base sites rendered NUC-7 one ideal platform for gas reservoir, specific catalyst, and luminescence sensing.

Lanthanide Coordination Polymers through Design for Exceptional Catalytic Performances in CO2 Cycloaddition Reactions

“…To assess the maneuvering performance, yields of the reactions using 0.50 and 0.031 mol % of the catalysts were additionally determined using mesitylene as the internal standard (entry 6 and 19), disclosing the satisfying values of >80% for Ib and >74% for IIb (Figures S11–S14). Compared with the other CPs/MOFs used in the reactions conducted under ambient CO 2 pressure and solvent-free condition (Table S7), ,− the TONs and TOFs reported here are worth noting as they are among the top-tier. In general, a long reaction time was required if complete conversion and high TONs were to be achieved, which on the other hand would aggravate the corresponding TOFs.…”

“…The coexistence of the Lewis acidic Eu III with vacant coordination sites and the Brønsted acidic −COOH and −OH as well as the Lewis basic −NN– bond, the phenyl rings, and the lone-paired electron containing O atoms in the vicinity of Eu III (Figure ) should, in principle, promote the catalytic activities of Ib and IIb. − …”

“…The copresence of Lewis acidic and basic motifs within the frameworks was also reported to enhance the catalysis since the Lewis basic motifs can help in transfixing CO 2 in close vicinity of the Lewis acid. Some previous CPs/MOFs devised based on this strategy were through the use of, for instance, the lone-paired electron containing N atom of 1,1′-(propane-1,3-diyl)­bis­(1 H -pyrazole-3,5-dicarboxylic acid) (PDC) in [Zn 3.5 (PDC) 2 (H 2 O) 10 ] and (5-5′-(1 H -1,2,4-triazole-3,5-diyl) diisophthalic acid in copper-based MOFs and the uncoordinated carboxylate O atoms in {[(CH 3 ) 2 NH 2 ]­[Zn II Tb III (TDP)­(H 2 O)]·3DMF·3H 2 O} n . Apart from the Lewis acidic and basic motifs, the catalytic activities of CPs/MOFs can also be improved in the presence of Brønsted acids, which may interact with both CO 2 and epoxide, e.g., −OH in [Zn 5 (OH) 2 (DBTA) 2 (H 2 O) 4 ] (H 4 DBTA = 2,2′-dihydroxy-1,1′-binaphthyl-3,3′,6,6′-tetrakis-(4-benzoic acid)) and −NH 2 as well as −COOH in [Zn 3 (L) 3 (H 2 L)·2DMF·H 2 O] (L = 2-aminoterephthalic acid) …”

“…The copresence of Lewis acidic and basic motifs within the frameworks was also reported to enhance the catalysis since the Lewis basic motifs can help in transfixing CO 2 in close vicinity of the Lewis acid. Some previous CPs/MOFs devised based on this strategy were through the use of, for instance, the lonepaired electron containing N atom of 1,1′-(propane-1,3diyl)bis(1H-pyrazole-3,5-dicarboxylic acid) (PDC) in [Zn 3.5 (PDC) 2 (H 2 O) 10 ] 20 and (5-5′-(1H-1,2,4-triazole-3,5diyl) diisophthalic acid in copper-based MOFs 21 and the 22 Apart from the Lewis acidic and basic motifs, the catalytic activities of CPs/ MOFs can also be improved in the presence of Brønsted acids, which may interact with both CO 2 and epoxide, e.g., −OH in [Zn 5 (OH) 2 (DBTA) 2 (H 2 O) 4 ] (H 4 DBTA = 2,2′-dihydroxy-1,1′-binaphthyl-3,3′,6,6′-tetrakis-(4-benzoic acid)) 23 and −NH 2 as well as 24 In the quest of high-performance catalysts, these strategies were considered and three new series of Ln III based CPs/ MOFs were fabricated using 3,3′,5,5′-azobenzenetetracarboxylic acid (H 4 abtc) as an organic linker; [Ln III According to the literature, 25 there is also a high tendency for at least one −COOH of H 4 abtc to remain protonated in the derived frameworks, which should be able to function as a Brønsted acid. Here, single-crystal structures of Ib (Eu III ), If (Ho III ), IIb (Eu III ), and IIIb (Eu III ) are described.…”

Nanochannel {InZn}–Organic Framework with a High Catalytic Performance on CO2 Chemical Fixation and Deacetalization–Knoevenagel Condensation

“…The excellent adsorption performance for CO 2 displayed by NUC-42a should be attributed to the coexisting Lewis acid–base sites including the exposed In III and Zn II sites, uncoordinated O carboxyl and N pyridine atoms, and the large conjugated π-electron system of TDP 6– , which render a much higher CO 2 concentration in the microporous channel, consequently facilitating the cycloaddition of epoxides with CO 2 around active sites. , Thereby, on the basis of the reported theoretical calculations and our experimental studies, − a proposed reaction mechanism during the chemical fixation of CO 2 catalyzed by NUC-42a is shown in Figure . First, epoxide is activated by the Lewis acid In III and Zn II sites along with the formation of a metal–epoxide adduct, leading to the unstable state of the ternary ring.…”