RESUMO
Precisely controlling the coordination microenvironment and electronic features of polynuclear secondary building units (SBUs) in coordination polymers (CPs) is an efficient approach to governing their fundamental performance. Here, different multinuclear SBUs (binuclear, trinuclear, and pentanuclear SBUs for 1-3, respectively) were introduced into Cd-based CPs, which were used as frictional electrode materials, to clarify the contributions of polynuclear Cd-SBUs through the output of triboelectric nanogenerators (TENGs). The results demonstrated that 1-TENG with binuclear Cd-SBUs possessed the highest output, whereas 3-TENG with the pentanuclear Cd-SBUs indicated the minimum output, suggesting that the binuclear Cd-SBUs in 1 lost electrons most readily and generated much more charge, which was further confirmed by density functional theory calculations. This work opened a new prospect to confirm the gaining/losing capability of polynuclear Cd-SBUs in CPs and provided an effective approach to tuning both the stability and functionality of polynuclear CPs as frictional pair materials to regulate the output of CPs-based TENGs.
RESUMO
A main difficulty in C-H bond functionalization is to undertake the catalyst control accurately where the reaction takes place. In this work, to achieve highly effective and regioselective single-site catalysts, a three-dimensional (3D) rhombus-like framework of {[Mn(Hidbt)DMF]·H2O}n (1) [H3idbt = 5,5'-(1H-imidazole-4,5-diyl)-bis(2H-tetrazole)] containing coordinated DMF molecules was constructed. For the dissolution-recrystallization structural transformation process, attractive structural transformations proceeded from 1 to a new crystalline species formulated as {[Mn3(idbt)2(H2O)2]·3H2O}n (2) with a 3D windowlike architecture, and then the Mn ions in 2 could be exchanged with Cu ions through cation exchange in a single-crystal to single-crystal fashion to produce the Cu-exchanged product {[Mn2Cu(idbt)2(H2O)2]·3H2O}n (2a), which had a windowlike framework like that of 2. Furthermore, 2 and 2a were used as heterogeneous catalysts for the regioselective C-H halogenation of phenols with N-halosuccinimides (NCS and NBS) to produce the site selective single monohalogenated products. It was found that the catalytic activity and site selectivity of 2a were much higher than those of 2, because the unique structural features of 2a with the uniformly dispersed CuII active centers served as a single-site catalyst with a site-isolated and well-defined platform to promote the C-H halogenation reaction in regiocontrol and guide an orientation that favored the para selectivity during the reaction process.
RESUMO
Precise control over the morphology and size of coordination polymers (CPs) is crucial for extending these inorganic-organic materials to many advanced applications, in particular for heterogeneous catalysis. In this work, two Zn-based CPs, {[Zn3(idbt)2(4,4'-dmbpy)2]·H2O}n (1) and {[Zn3(idbt)2(H2O)3]·H2O}n (2) (H3idbt = 5,5'-(1H-imidazole-4,5-diyl)-bis-(2H-tetrazole), 4,4'-dmbpy = 4,4''-dimethyl-2,2'-bipyridine), were synthesized through solvothermal reactions. The morphologies and particle sizes of 1 and 2 could be controlled from large scale to nanoscale by regulating the amount of poly(vinyl alcohol) (PVA). Furthermore, for the conversion reactions of nitromethylbenzenes into benzoic acids, the catalytic properties of nanoscale 1 and 2 were much more efficient than those of large size of 1 and 2, because of the benefit of readily accessible active sites in the nanoscale sized particles, which provide a tunable and functionalizable platform for the conversion reaction by minimizing the diffusion distance but do little for the selectivity.