Mass Transport Based on Covalent Organic Frameworks

ConspectusMass transport is fundamental to biological systems and industrial processes, governing chemical reactions, substance exchange, and energy conversion across various material scales. In biological systems, ion transport, such as proton migration through voltage-gated proton channels, regulates cellular potential, signaling, and metabolic balance. In industrial processes, transporting molecules through solid, liquid, or gas phases dictates reactant contact and diffusion rates, directly impacting reaction efficiency and conversion. Optimizing these processes necessitates the design of efficient interfaces or channels to enhance mass transport.Crystalline porous materials, particularly covalent organic frameworks (COFs), offer an excellent platform for investigating and optimizing mass transport. With ordered, pre-engineered nano- or subnanometer pores, COFs enable confined substance transport and garnered significant attention for energy conversion, catalysis, drug delivery, adsorption, and separation applications. Deeper investigations into the mass transport mechanism in COFs at the molecular level are crucial for advancing materials science, chemistry, and chemical engineering.Our group focuses on COFs to explore multisubstance cooperative transport mechanisms and structure-activity relationships for ions, water, and gases. We have expanded the linker chemistry of COFs by developing irreversible α-aminoketone-linked COFs and introducing the irreversible Suzuki coupling reaction into COF preparation. We proposed strategies such as side-chain-induced dipole-facilitated stacking and prenucleation and slow growth to achieve record large pore sizes and highly oriented nanochannels. We implemented exfoliation and an interwoven strategy to accelerate ion transport at complex interfaces, refined gas permeability in molecular sieve-based membranes through precise pore size engineering, and elucidated the effects of pore size and hydrophobicity/hydrophilicity on water phase transition and diffusion. Building on these insights, we designed novel open framework ionomers to tailor the microenvironment of electrocatalytic interfaces and uncovered multiple substance transport mechanisms. The synergistically enhanced transport of ions, water, and gas across three-phase interfaces effectively modulates the electrochemical CO₂ reduction reaction pathway and significantly boosts the power density of proton-exchange membrane fuel cells (PEMFCs).In this Account, we summarize recent advances in COF-based ion and molecular transport, emphasizing nanochannel construction strategies, including linkage, pore size, orientation, and function gradient modulations. We discuss the functional design of COFs, correlations between pore structure and transport properties, and their applications in gas separation, energy storage, and catalysis. Finally, we outline current challenges and future opportunities in synthetic chemistry, mass transport mechanisms, and applications. By understanding mass transport phenomena from microscopic particles to macroscopic scales, this Account aims to provide molecular design strategies for optimizing multisubstance transport across three-phase interfaces, aligning mass transport with reaction processes and offering insights to enhance catalytic efficiency and energy conversion performance.