MolX: Enhancing Large Language Models for Molecular Learning with A Multi-Modal Extension
Large language models (LLMs) exhibit limited molecular structural understanding—especially when relying solely on one-dimensional textual representations like SMILES—hindering their effectiveness in chemistry. Method: We propose MolX, a lightweight multimodal extension module that jointly encodes SMILES sequences, 2D molecular graphs (via GNNs), and expert-crafted molecular fingerprints. MolX is trained via multitask contrastive learning while keeping the LLM backbone frozen. Contribution/Results: MolX establishes the first “frozen-LLM + multimodal alignment” paradigm, introducing only 0.53%–0.82% additional trainable parameters. It achieves significant improvements over baselines across four downstream tasks—including molecule-to-text translation and retrosynthetic planning—while supporting both zero-shot inference and fine-tuning deployment. This enhances cross-task generalization of LLMs in chemistry without architectural modification or full-parameter adaptation.