About

The Xiao lab is a synthetic inorganic and materials chemistry group at the University of Washington.

Research topics

• Chemistry
• Organic chemistry
• Computer Science
• Nanotechnology
• Materials science
• Composite material
• Chemical physics
• Chemical engineering
• Physical chemistry
• Engineering

Selected publications

• Synthesis and crystal structures of a family of bimetallic complexes with phenyl-substituted bridging tetraoxolene ligands

  Acta Crystallographica Section C Structural Chemistry · 2025-05-01

  articleSenior author

  Seven dinuclear metal complexes and one trinuclear metal complex have been synthesized using the redox-active diphenyl-substituted tetraoxolene 2,5-dihydroxy-3,6-diphenyl-1,4-benzoquinone (H 2 Ph 2 dhbq, C 18 H 12 O 4 ) as a bridging ligand and tris[(pyridin-2-yl)methyl]amine (TPA, C 18 H 18 N 4 ) as a tetradentate terminal ligand. Single-crystal X-ray diffraction data confirm the final redox states of all components, revealing both expected and unexpected redox behavior across the eight reported complexes. Metal complexes with the formula [ M II 2 (Ph 2 dhbq 2− )(TPA) 2 ] 2+ can be synthesized from Mn, Fe, Co, Ni, Zn, and Ru, using either the oxidized ligand H 2 Ph 2 dhbq or a combination of the reduced ligand H 4 Ph 2 dhbq and an in-situ oxidant. Additionally, switching to Group 13 elements, such as Ga, facilitates the formation of the related [ M III 2 (Ph 2 dhbq 4− )(TPA) 2 ] 2+ complex, wherein the ligand remains in its initial reduced state.

  PublisherDOI

• Controlling Metal-Organic Framework Crystallization via Computer Vision and Robotic Handling

  ChemRxiv · 2025-04-11 · 1 citations

  preprint

  Traditional experimental techniques for metal–organic frameworks (MOFs) crystal growth are often time-consuming due to the need for manual bench chemistry and data analysis. In this study, we integrated laboratory automation with computer vision to accelerate the synthesis and characterization of Co-MOF-74, a framework containing coordinatively unsaturated Co(II) sites. By utilizing a liquid-handling robot, we significantly improved the efficiency of precursor formulation for solvothermal synthesis, saving approximately one hour of manual hands-on labor per synthesis cycle. We developed an accelerated characterization strategy using high-throughput optical microscopy and computer vision to identify the quality of crystallization outcomes. Our computer vision framework, Bok Choy, enables automated feature extraction from microscopic images, improving the analysis efficiency by approximately 35 times compared to manual analysis methods. Using this integrated workflow, we systematically performed a rapid screening of synthesis parameters and examined how each parameter influences the crystal morphology. Furthermore, by varying solvent compositions, we rapidly screened synthesis conditions that modulate crystal formation, identifying regimes that promote isolated crystallization, clustering, or lack of growth. The resulting structured dataset linking synthesis conditions to crystal morphology provides a scalable foundation for machine learning-driven materials discovery. The combination of high-throughput experimentation and automated data analysis establishes a cost-effective and widely applicable platform for accelerating the discovery and optimization of functional materials, with broad applications in catalysis, energy storage, and beyond.

  PublisherDOI

• Permanently porous cycloparaphenylene nanohoops <i>via</i> supramolecular engineering

  Chemical Science · 2025-11-20 · 3 citations

  articleOpen accessSenior authorCorresponding

  In this work, we establish carbon nanohoops as versatile tectons for permanently porous molecular crystals with well-defined supramolecular architectures, novel functionality, and surface areas exceeding 900 m 2 g −1 .

  PublisherOA PDFDOI

• Controlling metal–organic framework crystallization <i>via</i> computer vision and robotic handling

  Journal of Materials Chemistry A · 2025-01-01 · 4 citations

  articleOpen access

  A closed-loop robotic and computer vision system was developed to control and quantify MOF crystallization outcomes.

  PublisherOA PDFDOI

• Truncating 2D Framework Materials Down to a Single Pore: Synthetic Approaches and Opportunities

  Accounts of Chemical Research · 2025-05-19 · 5 citations

  articleSenior authorCorresponding

  ConspectusIn this Accounts article, we summarize our recent work on truncating conjugated two-dimensional framework materials down to a single pore, or a single macrocycle. Conjugated 2D architectures have emerged as one of the most synthetically adaptable motifs for coupling semiconductivity and porosity in metal-organic frameworks (MOFs) and covalent organic frameworks (COFs). However, despite their prevalence, 2D architectures have several limitations. In particular, the strong interlayer π-π stacking can limit both processability and the accessibility of internal active sites. We have found that simple macrocycles preserve key aspects of 2D framework structure and function, including porosity and out-of-plane electrical conductivity, while providing improved processability, surface tunability, and mass transport properties. In this article, we first describe our synthetic approach and general design considerations. Specifically, we show how ditopic analogues of the tritopic ligands commonly found in the synthesis of 2D MOFs and COFs can be used to achieve a diverse library of conjugated macrocycles that resemble fragments of semiconducting frameworks in both form and function. The length of the peripheral side chains, the size of the aromatic core, and the solubility of intermediates are all key variables in favoring selective macrocycle formation over undesired linear polymers and oligomers. Next, we highlight the unique advantages that macrocycles provide, including improved processability, atomically precise surface tunability, and greater active site accessibility. In particular, the identity of the peripheral side chains dramatically impacts both solubility and colloidal stability as well as crystal size and morphology. We further show how the solution processability and nanoscale dimensions of macrocycles can simplify electronic device fabrication and improve electrochemical performance. Finally, we end with a forward-looking discussion on how macrocycles offer a unique bridge between conjugated molecules and extended frameworks, enabling new application areas and fundamental science.

  PublisherDOI

• Permanently Porous Cycloparaphenylene Nanohoops via Supramolecular Engineering

  ChemRxiv · 2025-10-23

  articleSenior author

  Cycloparaphenylenes, also called carbon nanohoops, are a class of strained macrocycles recognized for their unique size-dependent optoelectronic properties, rich host–guest chemistry, and resemblance to carbon nanotubes. In this work, we establish carbon nanohoops as versatile tectons for permanently porous molecular crystals with well-defined supramolecular architectures and novel functionality. Using fluorinated nanohoops as precursors, we have synthesized seven new difluorodibenzodioxin-, methoxy-, and catechol boron bromide-functionalized derivatives. Structural characterization by single crystal X-ray and electron diffraction reveals porous structures stabilized by diverse noncovalent interactions, including π–π, CH–π, and boron–π interactions. In difluorodibenzodioxin nanohoops, robust intratubular π–π stacking guides the formation of nanotubular arrays with surface areas exceeding 700 m2/g. Remarkably, the nanotubular structure persists even in the presence of peripheral functionalization, enabling the formation of surface-decorated nanotubes. In contrast, boron bromide-derivatized nanohoops adopt an unusual 3D pore network that maximizes boron–π interactions. Due to the unique curvature of the carbon nanohoops, dense molecular packing is frustrated and the Lewis acidic boron centers remain partially exposed, leading to enhanced CO2 binding. Together, this work provides a blueprint on how substituted cycloparaphenylenes can be used to achieve permanently porous molecular materials with targeted structure and function.

  PublisherDOI

• A Recyclable Supramolecular Redox Mediator for Reductive Electrosynthesis

  Inorganic Chemistry · 2025-11-07 · 1 citations

  articleSenior authorCorresponding

  Redox mediators are often used in organic electrosynthesis to increase the rate of electron transfer between the electrode and substrate, allowing reactions to proceed at milder potentials and with greater selectivity. Herein, we highlight how supramolecular cages can provide unique benefits as redox mediators. Specifically, we show that tetrahedral [M4L6]8+ cages functionalized with redox-active perylene diimide (PDI) groups mediate the electroreduction of vicinal dihalides to the corresponding trans-alkenes. Relative to monomeric analogues, the cage architecture provides two key benefits. First, a greater than 2-fold rate enhancement was observed with the PDI-functionalized cage compared with a monomeric reference compound. The observed rate enhancement is attributed to the cage architecture, which limits the aggregation-induced inhibition of catalytic activity. In addition to its higher activity, the PDI cage is also fully recyclable. Due to changes in solubility upon electrochemical reduction, the cage reversibly deposits on the working electrode at the end of the reaction, allowing it to be readily recycled and reused up to five times with no loss in activity.

  PublisherDOI

• Engineering Bimetallic Active Sites in Metal–Organic Frameworks: Challenges and Opportunities

  Chemistry of Materials · 2024-05-15 · 15 citations

  articleSenior authorCorresponding

  Examples of two metal centers working synergistically to catalyze challenging chemical transformations can be found throughout biological and synthetic systems. In each case, specific metal identities, ligand environments, and metal–metal distances are required. The structural precision needed to engineer a productive, surface-supported bimetallic active site represents an opportunity for metal–organic frameworks. In this perspective, we summarize the different ways binuclear metal active sites have been synthesized in metal–organic frameworks and applied in catalysis. Selected examples from the literature will be highlighted to illustrate both the diversity of synthetic approaches as well as the diversity of bimetallic structures.

  PublisherDOI

• Controlling the crystal packing and morphology of metal–organic macrocycles through side-chain modification

  ChemRxiv · 2024-05-05 · 1 citations

  preprintOpen accessSenior author

  Supramolecular nanotubes constructed from the self-assembly of conjugated metal–organic macrocycles provide a unique collection of materials properties, including solution processability, porosity, and electrical conductivity. Here we show how small modifications to the macrocycle periphery subtly alter the noncovalent interactions governing self-assembly, leading to large changes in crystal packing, crystal morphology, and materials properties. Specifically, we synthesized five distinct copper-based macrocycles that differ in either the steric bulk, polarity, or hydrogen-bonding ability of the peripheral side-chains. We show that increased steric bulk leads to more disordered π–π stacking and lower electrical conductivity, whereas hydrogen-bonding groups lead to more ordered intermolecular interactions and a dramatic increase in crystallite size. Together, these results establish side-chain engineering as a rich toolkit for controlling the packing structure, particle morphology, and bulk properties of conjugated metal–organic macrocycles.

  PublisherOA PDFDOI

• Nitrogen‐Rich Conjugated Macrocycles: Synthesis, Conductivity, and Application in Electrochemical CO ₂ Capture

  Angewandte Chemie · 2024-12-05

  articleOpen accessSenior authorCorresponding

  Abstract Here we report a series of nitrogen‐rich conjugated macrocycles that mimic the structure and function of semiconducting 2D metal–organic and covalent organic frameworks while providing greater solution processability and surface tunability. Using a new tetraaminotriphenylene building block that is compatible with both coordination chemistry and dynamic covalent chemistry reactions, we have synthesized two distinct macrocyclic cores containing Ni−N and phenazine‐based linkages, respectively. The fully conjugated macrocycle cores support strong interlayer stacking and accessible nanochannels. For the metal–organic macrocycles, good out‐of‐plane charge transport is preserved, with pressed pellet conductivities of 10 −3 S/cm for the nickel variants. Finally, using electrochemically mediated CO 2 capture as an example, we illustrate how colloidal phenazine‐based organic macrocycles improve electrical contact and active site electrochemical accessibility relative to bulk covalent organic framework powders. Together, these results highlight how simple macrocycles can enable new synthetic directions as well as new applications by combining the properties of crystalline porous frameworks, the processability of nanomaterials, and the precision of molecular synthesis.

  PublisherOA PDFDOI

Recent grants

• CAREER: Bifunctional and Bimetallic Single-Site Catalysts for Sustainable Synthesis

  NSF · $741k · 2022–2027

Frequent coauthors

• Jeffrey R. Long

  University of California, Berkeley

  65 shared

• Jarad A. Mason

  43 shared

• Matthew R. Hudson

  NIST Center for Neutron Research

  39 shared

• Craig M. Brown

  NIST Center for Neutron Research

  26 shared

• Laura Gagliardi

  University of Chicago

  22 shared

• Lucy E. Darago

  22 shared

• Matthew T. Kapelewski

  ExxonMobil (United States)

  19 shared

• Ashlyn A. Kamin

  University of Washington

  19 shared

Labs

• Xiao LabPI

Awards & honors

• NSF GRFP award
• honorable mention recipients
• CPP manuscript publication
• Inorganic Chemistry publication
• Accounts of Chemical Research article