Truxene-based porous polymers synthesized through the simple "solvent knitting" strategy from hexamethyl or tribenzyl truxene-based monomers (TxPP1 and TxPP2), and their corresponding TxPP@TiO2 hybrids are used as photocatalysts for H2 production from water using methanol as sacrificial agent, under UV-Vis light. These polymers present higher hydrogen evolution rate (HER) than TiO2, and remarkable thermo-and photo-stabilities. Hybrids TxPP-TiO2 exhibited intensely enhanced photocatalytic activity compared to TiO2 or TxPPs alone. In the presence of platinum (1%) as cocatalyst, HER from TxPP1@T-10 significantly boosted reaching values above 21000 µmol.g -1 .h -1 which to the best of our knowledge, represents the highest HER reported for hybrids based on TiO2 and conjugated porous polymers. Interestingly, small structural differences of the corresponding truxene monomers result in different photocatalytic behavior. We focused here on gaining insight on the charge transfer mechanism and rationalizing the different photocatalytic performances in order to establish clear structure-activity relationships. In fact, photoluminescence and transient absorption spectroscopy demonstrated that the remarkably enhanced photocatalytic activity of the most active hybrids (TxPP1@TiO2) can be attributed to the efficiently photogenerated electron-hole separation by a direct Z-scheme mechanism, while lower 2 performance of TxPP2@TiO2, is probably due to a less efficient heterojunction type II charge transfer mechanism.

In 2011, a new type of hyper-cross-linked polymers (HCPs) arose, known as knitting aromatic polymers (KAPs), characterized by their extraordinary chemical and thermal stability, by their porosity properties, and above all, for the simplicity of their synthesis based on the union of aromatic monomers, without any previous functionalization. The next logical step was the incorporation of metals within these networks, as support for different soluble molecular catalysts or metal nanoparticles (NPs). Thus, the number of metal-containing KAPs has been gradually growing in the past decade, and we have considered that now, in the 10th anniversary of the first KAPs reported, a review of all the metal-containing KAPs and their application as heterogeneous metal catalysts is mandatory. In this review, the most relevant characteristics of all KAPs that contain metals are summarized, divided into two large groups, either as metal complexes or as metal NPs, and classified according to the type of metal incorporated. Finally, the catalytic activities were compared based on the metal employed in each studied reaction, and the future goals of these types of materials are commented on.

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