RESUMEN
Through in-depth study of the properties and reaction mechanisms of catalysts, it is possible to better optimize catalytic systems and improve reaction efficiency and selectivity. This remains one of the challenges in the field of catalysis. Therefore, the research and design of catalysts play crucial roles in understanding and optimizing catalytic reaction mechanisms. A robust 2D zinc-based MOFs (Zn-HA) supported Co(II) ion catalyst (Zn-HA@Co) has been designed and synthesized via a coordination-assisted strategy for ß-alkylation of secondary alcohols with primary alcohols. The characterization demonstrated that the anchoring of Co(II) on Zn-HA via coordination could efficiently enhance the Co(II) ion dispersity and interaction between Co(II) and Zn-HA MOFs. Importantly, the density functional theory results have provided mechanistic insights into the energy of the HOMO and LUMO of the Zn-HA@Co catalyst as well as the energy change of the entire process after interacting with the reactants and the specific energy changes of each orbital. The synthesized Zn-HA@Co MOFs effectively lower the energy barrier of the catalytic reaction process. We expect that our research and design of catalysts will serve as valuable guideline for understanding and optimizing catalytic reaction mechanisms.
RESUMEN
This study investigates the enhancement of hydraulic lime mortar (HLM) using varying contents of metakaolin (MK) to improve its application in the restoration of historic buildings. Samples from historic structures were analyzed, and the effects of different MK contents on the physical and mechanical properties of HLM were examined. The reaction mechanism and microstructural changes were evaluated using XRD and SEM analysis. The results indicated that increasing MK levels in HLM led to a decrease in fluidity, with fluidity reducing by 4.8% at 12% MK. The addition of MK increased water consumption for standard consistency by 5.4% and shortened the final setting time by 10.2%. MK consumption promoted secondary hydration, enhancing compressive strength by up to 98.1% and flexural strength by up to 55.1%, and increasing bonding strength by 26.9%. The density of HLM improved with MK addition, slightly reducing moisture content by 4.5% and water absorption by 4.6%, while the water vapor transmission properties decreased by 50.9%, indicating reduced porosity. The elastic modulus of the mortar increased significantly from 2.19 GPa to 7.88 GPa with the addition of MK, enhancing rigidity and crack resistance. The optimal blend for restoration materials was found to be 9.0% MK and 25.0% heavy calcium carbonate and was characterized by moderate mechanical strength, enhanced early strength, commendable permeability, minimal risk of cracking, and ease of application. This blend is highly suitable for the rehabilitation of historic structures.