Prevalent in consumer goods, electronic devices, and medical implants, vulcanized polysiloxanes are a highly versatile class of materials.  This need to address versatile applications confers both benefits and synthetic challenges, most notably the design of catalyst systems that facilitate rapid, robust, and efficient syntheses while limiting cost and environmental or physiological toxicity.  To address this challenge, this work introduces a novel metal- and solvent-free approach to the vulcanization of polysiloxanes.  The reaction of poly(methylhydrosiloxane) with a range of mono- and diketone crosslinkers, facilitated by the metal-free catalyst tris-(pentafluorophenylborane), affords a large family of vulcanized polysiloxane gels with crosslink densities tunable by variation of both polymer functionality and crosslinker structure.  We anticipate that these findings will contribute to the development of environmentally benign alternatives to transition metal catalysts and promote the expansion of vulcanized polysiloxanes to additional applications.