Alkali metal cation doping of metal-organic framework for enhancing carbon dioxide adsorption capacity

Metal-organic frameworks （MOFs） have attracted much attention as adsorbents for the separation of CO2 from flue gas or natural gas. Here, a typical metal-organic framework HKUST-I（also named Cu-BTC or MOF-199） was chemically reduced by doping it with alkali metals （Li, Na and K） and they were further used to investigate their CO2 adsorption capacities. The structural information, surface chemistry and thermal behavior of the prepared adsorbent samples were characterized by X-ray powder diffraction （XRD）, thermo-gravimetric analysis （TGA） and nitrogen adsorption-desorption isotherm analysis. The results showed that the CO2 storage capacity of HKUST-1 doped with moderate quantities of Li＋, Na＋ and K＋, individually, was greater than that of unmodified HKUST-1. The highest CO2 adsorption uptake of 8.64 mmol/g was obtained with 1K-HKUST-1, and it was ca. 11% increase in adsorption capacity at 298 K and 18 bar as compared with HKUST- 1. Moreover, adsorption tests showed that HKUST-1 and 1K-HKUST-1 displayed much higher adsorption capacities of CO2 than those of N2. Finally, the adsorption/desorption cycle experiment revealed that the adsorption performance of 1K-HKUST-1 was fairly stable, without obvious deterioration in the adsorption capacity of CO2 after 10 cycles.

Studies on basicity of alkali metal catron exchanged β and X zeolites by pyrrole-IR spectroscopy

The strength of basic sites has been measured by pyrrole-IR on alkali metal cation exchanged β and X zeolites, as well as NaOH loaded Naβ. The influence of cation type and the structure of zeolites on their basicity has been studied. The acidic and basic properties of the samples were investigated by NH3-TPD and isopropanol reaction. It was shown that the strength of basic sites on samples could be characterized by the shift of vNH band in the pyrrole-IR spectra. The framework oxygen charges were calculated from the Sanderson electronegativity. The changes in basic properties with various alkali metal cation are consistent with the changes of local oxygen charges of the zeolite framework.

Electrifying the future:the advances and opportunities of electrocatalytic carbon dioxide reduction in acid

Transforming carbon dioxide(CO_(2))into products using renewable electricity is a crucial and captivating quest for a green and circular economy.Compared with commonly used alkali electrolytes,acidic media for electrocatalytic CO_(2) reduction(CO_(2)RR)boasts several advantages,such as high carbon utilization efficiency,high overall energy utilization rate,and low carbonate formation,making it a compelling choice for industrial applications.However,the acidic CO_(2)RR also struggles with formidable hurdles,encompassing the fierce competition with the hydrogen evolution reaction,the low CO_(2) solubility and availability,and the suboptimal performance of catalysts.This review provides a comprehensive overview of the CO_(2)RR in acidic media.By elucidating the underlying regulatory mechanism,we gain valuable insights into the fundamental principles governing the acidic CO_(2)RR.Furthermore,we examine cutting-edge strategies aimed at optimizing its performance and the roles of reactor engineering,especially membrane electrode assembly reactors,in facilitating scalable and carbon efficient conversion.Moreover,we present a forward-looking perspective,highlighting the promising prospects of acidic CO_(2)RR research in ushering us towards a carbon-neutral society.