Enhanced Gas Adsorption on Cu3(BTC)2 Metal-Organic Framework by Post-Synthetic Cation Exchange and Computational Analysis

Increased gas adsorption in a series of post-synthetically modified metal-organic frameworks (MOFs) of the type HKUST-1 was achieved by the partial cation exchange process. Manipulation of post-synthetic conditions demonstrates high tunability in the site substitution and gas adsorption properties during the dynamic equilibrium process. In this work, post-synthetic modification of Cu₃(BTC)₂ is carried on by exposure to TM²⁺ solutions (TM = Mn, Fe, Co, Ni) at different time intervals. The crystal structure, composition, and morphology were studied by powder X-ray diffraction, Fourier-transform infrared spectroscopy, inductively coupled plasma optical emission spectroscopy, and scanning electron microscopy. Structural analysis supports the retention of the crystal structure and partial substitution of the Cu metal nodes within the framework. A linear increase in the transmetalation process is observed with Fe and Co with a maximum percentage of 39 and 18%, respectively. Conversely, relatively low cation exchange is observed with Mn having a maximum percentage of 2.40% and Ni with only 2.02%. Gas adsorption measurements and surface area analysis were determined for each species. Interestingly, (Cu/Mn)₃(BTC)₂ revealed the highest CO₂ adsorption capacity of 5.47 mmol/g, compared to 3.08 mmol/g for Cu₃(BTC)₂. The overall increased gas adsorption can be attributed to the formation of defects in the crystal structure during the cation exchange process. These results demonstrate the outstanding potential of post-synthetic ion exchange as a general approach to fine-tuning the physical properties of existing MOF architectures.

Alcohol self-administration and nicotine withdrawal alter biomarkers of stress and inflammation and prefrontal cortex changes in Gβ subunits

Background: Although alcohol and nicotine are often used together, the biological consequences of these substances are not well understood. Identifying shared targets will inform cessation pharmacotherapies and provide a deeper understanding of how co-use of alcohol and nicotine impacts health, including biomarkers of stress and inflammation.Objective: We examined the effects of nicotine exposure and withdrawal on alcohol self-administration (SA), stress and inflammatory biomarkers, and a G-protein coupled receptor subunit (Gβ) in brain areas associated with drug use.Methods: Male rats were trained to SA alcohol and then received a nicotine pump (n = 7-8 per group). We assessed alcohol intake for 12 days during nicotine exposure and then following pump removal to elicit withdrawal. After the behavioral studies, we assessed plasma leptin, corticosterone, and interleukin-1β (IL-1β), and Gβ protein expression in the amygdala, nucleus accumbens (NAc), and prefrontal cortex (PFC).Results: Nicotine exposure or withdrawal did not alter alcohol intake (p > .05). Alcohol and nicotine withdrawal elevated corticosterone levels (p = .015) and decreased Gβ levels in the PFC (p = .004). In the absence of nicotine, alcohol SA suppressed IL-1β levels (p = .039). Chronic exposure to nicotine or withdrawal during alcohol SA did not alter leptin levels or Gβ expression in the amygdala or NAc (p's > .05).Conclusions: The combination of alcohol SA and nicotine withdrawal produced a persistent increase in stress biomarkers and a suppression in Gβ expression in the PFC, providing an important first step toward understanding the common biological mechanisms of alcohol/nicotine misuse.