Porosity plays a clearly important role in geology. It controls fluid storage in aquifers, oil and gas fields and geothermal systems, and the extent and connectivity of the pore structure control fluid flow and transport through geological formations, as well as the relationship between the properties of individual minerals and the bulk properties of the rock. In order to quantify the relationships between porosity, storage, transport and rock properties, however, the pore structure must be measured and quantitatively described. The overall importance of porosity, at least with respect to the use of rocks as building stone was recognized by TS Hunt in his “Chemical and Geological Essays” (1875, reviewed by JD Dana 1875) who noted:

Over the past two decades there has been heightened concern about, and an improving scientific description of, the impacts of increasing carbon dioxide concentrations in Earth’s atmosphere. Despite this concern, the global rate of addition of carbon dioxide to the atmosphere by the burning of fossil fuel, now approaching 10 Gton C/yr, continues to increase, and at an accelerating rate (Fig. 1a). Although many still hope and believe that carbon emissions can be arrested at near the current rates, and decreased over the remainder of the 21^st century, there is as yet little evidence that this is...

Metal-Organic Frameworks (MOF) have been identified as highly efficient nanoporous adsorbents for CO₂ storage. In particular, Mg-MOF-74 has been shown to promise exceptionally high CO₂ sorption. Although several studies have reported adsorption isotherms of CO₂ in Mg-MOF-74, the effect of inter-crystalline spacing in Mg-MOF-74 on the sorption of CO₂ has not been addressed. These effects have been shown to be profound for a quadrupolar molecule like CO₂ in the case of silicalite (Phys. Chem. Chem. Phys. 22 (2020) 13951). Here, we report the effects of inter-crystalline spacing on the adsorption of CO₂ in Mg-MOF-74, studied using grand canonical Monte Carlo (GCMC) simulations. The inter-crystalline spacing is found to enhance adsorption at the crystallite surfaces. Larger inter-crystalline spacing up to twice the kinetic diameter of CO₂ results in higher adsorption and larger crystallite sizes suppress adsorption. Magnitudes of the inter-crystalline space relative to the kinetic diameter of the adsorbed fluid and the surface to volume ratio of the adsorbent crystallites are found to be important factors determining the adsorption amounts. The results of this study suggest that the ideal Mg-MOF-74 sample for CO₂ storage applications should have smaller crystallites separated from each other with an inter-crystalline space of approximately twice the kinetic diameter of CO₂.

Throughout Earth’s crust and upper mantle, fluids play the dominant role in transporting and concentrating Earth’s energy and mineral resources (Liebscher and Heinrich 2007). Furthermore, the flux of fluids, which act as both reaction media and reactants, strongly influences the genesis and evolution of many different kinds of rocks. Among many different types of fluids, those containing volatile carbon, hydrogen and oxygen (C-H-O) species tend to dominate in the lithosphere along with various electrolytes and silica. These fluids commonly contain methane as both a major constituent and an important energy source. Conventional natural gas deposits reside in sedimentary...

Research in the deep terrestrial biosphere is driven by interest in novel biodiversity and metabolisms, biogeochemical cycling, and the impact of human activities on this ecosystem. As this interest continues to grow, it is important to ensure that when subsurface investigations are proposed, materials recovered from the subsurface are sampled and preserved in an appropriate manner to limit contamination and ensure preservation of accurate microbial, geochemical, and mineralogical signatures. On February 20th, 2014, a workshop on “Trends and Future Challenges in Sampling The Deep Subsurface” was coordinated in Columbus, Ohio by The Ohio State University and West Virginia University faculty, and sponsored by The Ohio State University and the Sloan Foundation’s Deep Carbon Observatory. The workshop aims were to identify and develop best practices for the collection, preservation, and analysis of terrestrial deep rock samples. This document summarizes the information shared during this workshop.