# Cluster-Engineered Titanium Metal−Organic Aerogels as Tunable Platforms for Post-synthetic Doping and Enhanced Photocatalytic Hydrogen Production

## TL;DR

Researchers created titanium-based metal-organic aerogels that can be modified to enhance their ability to produce hydrogen through photocatalysis.

## Contribution

A new two-step synthesis method for titanium-based MOAs with tunable post-synthetic doping for improved photocatalytic performance.

## Key findings

- The MOAs retained Ti8 clusters and had uncoordinated -COOH groups for catalyst incorporation.
- Functionalization with Ru- and Cu-terpyridine complexes achieved the highest hydrogen production rates.
- The system showed stable performance for up to 24 hours under LED irradiation.

## Abstract

Metal−organic gels (MOGs) and their derived aerogels
(MOAs) offer an alternative to crystalline MOFs, combining the coordination-driven
tunability with the flexibility, hierarchical porosity, and easy processability
of sol–gel polymers. Their noncrystalline nature enables the
integration of functional units without crystallization constraints,
facilitating diverse uses, and drawing recent attention for photocatalytic
applications. Herein we report the design of a new approach to prepare
a titanium-based MOA synthesized via a two-step strategy involving
a preformed titanium oxo-cluster ([Ti8O8(benzoato)16]), and a subsequent ligand exchange with benzene-1,3,5-tricarboxylato
ligands. A combined chemical, microstructural, and NEXAFS analysis
confirms the retention of Ti8 cluster and the presence
of uncoordinated −COOH groups after meso-macroporous gel formation.
Those enabled a subsequent homogeneous incorporation of single-atom
site co-catalysts via coordination with Ru, Co, Ni, and Cu complexes
bearing terpyridine, bipyridine, and phenanthroline N-ligands. Photocatalytic
hydrogen evolution under 365 nm LED irradiation exhibited significant
activity (110 μmol·g–1·h–1), which further increased upon functionalization. The MOAs functionalized
with Ru- and Cu-terpyridine complexes showed the highest performance
(167 and 164 μmol·g–1·h–1, respectively), surpassing even Pt-loaded analogues and highlighting
the role of terpyridine in facilitating multielectron storage. The
system also showed stable long-term performance up to 24 h.