High-Performance, Scalable Wood-Based Filtration Device with a Reversed-Tree Design

Water shortage is one of the most pressing challenges across the world. Wood, a natural and sustainable material, possesses a unique hierarchical three-dimensional (3D) interconnected microstructure featuring vertically aligned microchannels (vessels and tracheids) along the tree growth direction that are lined with micropores (ray cells, pits, and nanopores). This structure renders wood highly desirable for a wide range of emerging applications and particularly as a cost-effective filtration material. Herein, we demonstrate a novel “cross-flow” filtration device based on a wood filter decorated with Pd nanoparticles, in which methylene blue (MB) transports perpendicular to the longitudinal direction through ray cells, pits, and nanopores, as well as along the longitudinal direction through the vessel channels and tracheids. In this manner, we achieve strong MB–catalyst interactions by the intermittent changes in the flow direction (i.e., a breakdown of the unidirectional nature of water transport) that are generated as the MB flows through the small-diameter micropores and along the microchannel structure. Consequently, the device exhibits excellent performance for the reduction of MB with a high flow rate of up to 1.6 × 104 L kg–1 h–1, a high treatment efficiency of ∼99%, and a high turnover frequency of 2.2 molMB molPd–1 min–1, representing the highest value among various reported Pd-based catalytic devices. This high-performance wood-based cross-flow filtration device provides a new material platform for the efficient reduction of MB, which can be extended to a range of other materials such as organic pollutants and heavy metal removal.