Thermochemistry of a Biomimetic and Rubisco-Inspired CO2 Capture System from Air

Abstract

In theoretical studies of chemical reactions the reaction thermochemistry is usually reported for the stoichiometric reaction at standard conditions (∆G˝, ∆H˝, ∆S˝). We describe the computation of the equilibrium concentrations of the CO 2-adducts for the general capture reaction CO 2 + Capture System Õ CO 2-adduct (GCR) and the rubisco-type capture reaction CO 2 + Capture System Õ CO 2-adduct + H 2 O (RCR) with consideration of the reaction CO 2 (g) Õ CO 2 (aq) via Henry's law. The resulting equations are evaluated and graphically illustrated as a function of atmospheric CO 2 concentration and as a function of temperature. The equations were applied to the thermochemistry of small molecule rubisco-model reactions and series of additional model reactions to illustrate the range of the Gibbs free enthalpy for the effective reversible capture and of the reaction entropy for economic CO 2 release at elevated temperature. A favorable capture of free enthalpy is of course a design necessity, but not all exergonic reactions are suitable CO 2 capture systems. Successful CO 2 capture systems must allow for effective release as well, and this feature is controlled by the reaction entropy. The principle of using a two-pronged capture system to ensure a large negative capture entropy is explained and highlighted in the graphical abstract. It is hoped that the presentation of the numerical examples provides useful guidelines for the design of more efficient capture systems.

Exceptionally High CO2 Adsorption at 273 K by Microporous Carbons from Phenolic Aerogels: The Role of Heteroatoms in Comparison with Carbons from Polybenzoxazine and Other Organic Aerogels

“…Equations (1) and (2) are proposed based on extensive theoretical work on CO 2 capture via solution‐phase formation of carbamate with, for example, methylamine, and follow the same enthalpic/entropic arguments . Specifically, given that CO 2 entering micropores has already paid a severe entropic penalty, and thus considering bond energies alone, Equation (1) is slightly endothermic (by about 17 kcal mol −1 ), while Equation (2) is about energy neutral.…”

“…Equations (1) and (2) are proposed based on extensive theoretical work on CO 2 capture via solution-phase formation of carbamate with, for example, methylamine, and follow the same enthalpic/entropic arguments. [75][76][77] Specifically, given that CO 2 entering micropores has already paid a severe entropic penalty, [78] and thus considering bond energies alone, Equation (1) is slightly endothermic (by about 17 kcal mol −1 ), while Equation (2) is about energy neutral. Those estimates support: a) the higher Q 0 values for RES-derived carbons relative to those from PBO and PA, and b) the much higher uptake of CO 2 by EC-RF-D and EC-RF-O relative to EC-PBO, which has practically identical material properties with the former two, as discussed above.…”

A search for selectivity to enable CO2 capture with porous adsorbents

“…3B). 40 This mechanism developed during millions of years by nature for efficient CO 2 capture may serve as an inspiration to create similar, but potentially even more effective sorption materials. For illustration: a binding of one CO 2 molecule per at least 52 000 mass units and the rather poor dynamics would indeed be difficult to accept from a technical system.…”

From Molecular Precursors to Nanoparticles—Tailoring the Adsorption Properties of Porous Carbon Materials by Controlled Chemical Functionalization

“…Nature is impressively showing how precisely adsorption properties can be tuned if these functionalization tools are wisely combined and site‐specific interaction is provided. Some of the examples are an enzyme found in plants with the most selective CO 2 capture mechanism, Ribulose‐1,5‐bisphosphate carboxylase/oxygenase (RubisCO),20a,26 carbonic anhydrase that converts and transports CO 2 , and metalloprotein hemoglobin that has the function to transport O 2 in vertebrates 27b,28. Inspired by the control that nature achieves, materials chemists are more and more focusing on the development of methods for transferring these principles from biology to carbon‐based materials.…”