Ordered open channels found in two-dimensional covalent organic frameworks (2D COFs) could enable them to adsorb carbon dioxide. However, the frameworks dense layer architecture results in low porosity that has thus far restricted their potential for carbon dioxide adsorption. Here we report a strategy for converting a conventional 2D COF into an outstanding platform for carbon dioxide capture through channel-wall functionalization. The dense layer structure enables the dense integration of functional groups on the channel walls, creating a new version of COFs with high capacity, reusability, selectivity, and separation productivity for flue gas. These results suggest that channel-wall functional engineering could be a facile and powerful strategy to develop 2D COFs for high-performance gas storage and separation.Covalent organic frameworks (COFs), a class of crystalline porous polymers that allow the atomically precise integration of building blocks into periodicities, have emerged as a new platform for designing advanced organic materials with periodic structures. [1][2][3][4][5] Two-dimensional (2D) COFs have limited surface areas and small pore volumes as a result of their dense p-stacking layer structure, which greatly restricts their potential as a porous medium for the adsorption of gases such as carbon dioxide, methane, and hydrogen. With the exception of two examples utilizing azine [2b] and boronate [3d] linkages that interact with specific gas molecules to exhibit good capacity, the majority of 2D COFs have very low performance in gas adsorption. To improve this situation, we present a strategy that explores the channel walls for functional engineering and demonstrate its significance and effectiveness in the design of 2D COFs for high-performance gas adsorption and separation.The advantage of the dense layer structure of 2D COFs is that this architecture enables the dense incorporation of functional groups onto the channel walls. This structural benefit compensates for the low porosity of 2D COFs. We observed that functional engineering of the channel walls converts a conventional 2D COF into an outstanding carbondioxide-capture material. We demonstrated this strategy by using a conventional imine-linked 2D COF (Figure 1 a,b, [HO] 100 % -H 2 P-COF) as a scaffold with porphyrin at the vertices and phenol units on the pore walls; this 2D COF exhibits a low capacity for carbon dioxide adsorption. The phenol groups undergo a quantitative ring opening reaction with succinic anhydride that decorates the channel walls with open carboxylic acid groups (Figure 1 a,c, [HO 2 C] 100 % -H 2 P-COF). The content of carboxylic acid units on the channel walls was tuned by adjusting the content of phenol groups through a three-component condensation system with a mixture of 2,5-dihydroxyterephthalaldehyde (DHTA) and 1,4-phthalaldehyde (PA) as the wall components (Figure 1 ). Various analytic methods revealed that the DHTA-to-PA molar ratios integrated into [HO] X % -H 2 P-COFs were identical to those empl...

Ordered π-columns and open nanochannels found in covalent organic frameworks (COFs) could render them able to store electric energy. However, the synthetic difficulty in achieving redox-active skeletons has thus far restricted their potential for energy storage. A general strategy is presented for converting a conventional COF into an outstanding platform for energy storage through post-synthetic functionalization with organic radicals. The radical frameworks with openly accessible polyradicals immobilized on the pore walls undergo rapid and reversible redox reactions, leading to capacitive energy storage with high capacitance, high-rate kinetics, and robust cycle stability. The results suggest that channel-wall functional engineering with redox-active species will be a facile and versatile strategy to explore COFs for energy storage.

Secondary active transporters use electrochemical gradients provided by primary ion pumps to translocate metabolites or drugs "uphill" across membranes. Here we report the ion-coupling mechanism of cystinosin, an unusual eukaryotic, proton-driven transporter distantly related to the proton pump bacteriorhodopsin. In humans, cystinosin exports the proteolysis-derived dimeric amino acid cystine from lysosomes and is impaired in cystinosis. Using voltage-dependence analysis of steady-state and transient currents elicited by cystine and neutralization-scanning mutagenesis of conserved protonatable residues, we show that cystine binding is coupled to protonation of a clinically relevant aspartate buried in the membrane. Deuterium isotope substitution experiments are consistent with an access of this aspartate from the lysosomal lumen through a deep proton channel. This aspartate lies in one of the two PQ-loop motifs shared by cystinosin with a set of eukaryotic membrane proteins of unknown function and is conserved in about half of them, thus suggesting that other PQ-loop proteins may translocate protons.